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Recent Applications of Magnetic Solid-phase Extraction for Sample Preparation

August 2019
Chromatographia 82(8)

August 2019
82(8)

DOI:10.1007/s10337-019-03721-0

Authors:

Chiara Cavaliere

Sapienza University of Rome

Giorgia la barbera

Sapienza University of Rome

Carmela maria Montone

Sapienza University of Rome

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This minireview is dedicated to the discussion of analytical methods based on magnetic solid-phase extraction for the investigation of different analyte classes in complex matrices. Magnetic solid-phase extraction represents one of the most exploited approaches for sample preparation, which benefits from the development of new materials and from the coupling with other purification and clean-up strategies. New materials are continuously described for the isolation and enrichment of a variety of compounds, from small molecules to biologic macromolecules. Such magnetic materials developed for magnetic solid-phase extraction are discussed in this minireview, spanning across different types of materials, from the more traditional magnetic nanoparticles functionalized with polymers, to molecularly imprinted polymers, but also graphene, carbon nanotubes, graphitized carbon black, metal organic frameworks, covalent organic frameworks, composite materials, biopolymers (polydopamine, chitosan), materials from wastes and natural products and the newly introduced knitting aromatic polymers. The magnetic solid-phase extraction methods are collected from the recent literature and organized in sections based on the target analyte classes, which include drugs, endocrine-disrupting compounds, pesticides, polycyclic aromatic hydrocarbons, metals, toxins, peptides, proteins, metabolites and a final chapter dedicated to applications to other common pollutants, contaminants and multiresidue methods. A selection of recent applications and variations of the traditional magnetic solid-phase extraction protocols is discussed for food, environmental and biologic matrices. Finally, the compliance of magnetic solid-phase extraction with the principles of green analytical chemistry is also briefly discussed, with recent examples, indicating the use of waste or sustainable materials, development of green material preparations and reduction of organic solvents as the main strategies for future development of environmentally friendly magnetic solid-phase extraction methods. Graphical Abstract Open image in new window

Graphical representation of the main steps involved in an MSPE protocol

…

Development of MSPE since the introduction in 1999. Milestones antecedent to the definition of MSPE but conceptually related are also shown in shaded colours

…

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Chromatographia (2019) 82:1251–1274

https://doi.org/10.1007/s10337-019-03721-0

REVIEW

Recent Applications ofMagnetic Solid‑phase Extraction forSample

Preparation

AnnaLauraCapriotti1· ChiaraCavaliere1· GiorgiaLaBarbera1· CarmelaMariaMontone1· SusyPiovesana1 ·

AldoLaganà1

Received: 3 January 2019 / Revised: 18 March 2019 / Accepted: 11 April 2019 / Published online: 24 April 2019

Abstract

This minireview is dedicated to the discussion of analytical methods based on magnetic solid-phase extraction for the investi-

gation of diﬀerent analyte classes in complex matrices. Magnetic solid-phase extraction represents one of the most exploited

approaches for sample preparation, which beneﬁts from the development of new materials and from the coupling with other

puriﬁcation and clean-up strategies. New materials are continuously described for the isolation and enrichment of a variety

of compounds, from small molecules to biologic macromolecules. Such magnetic materials developed for magnetic solid-

phase extraction are discussed in this minireview, spanning across diﬀerent types of materials, from the more traditional

magnetic nanoparticles functionalized with polymers, to molecularly imprinted polymers, but also graphene, carbon nano-

tubes, graphitized carbon black, metal organic frameworks, covalent organic frameworks, composite materials, biopolymers

(polydopamine, chitosan), materials from wastes and natural products and the newly introduced knitting aromatic polymers.

The magnetic solid-phase extraction methods are collected from the recent literature and organized in sections based on the

target analyte classes, which include drugs, endocrine-disrupting compounds, pesticides, polycyclic aromatic hydrocarbons,

metals, toxins, peptides, proteins, metabolites and a ﬁnal chapter dedicated to applications to other common pollutants,

contaminants and multiresidue methods. A selection of recent applications and variations of the traditional magnetic solid-

phase extraction protocols is discussed for food, environmental and biologic matrices. Finally, the compliance of magnetic

solid-phase extraction with the principles of green analytical chemistry is also brieﬂy discussed, with recent examples,

indicating the use of waste or sustainable materials, development of green material preparations and reduction of organic

solvents as the main strategies for future development of environmentally friendly magnetic solid-phase extraction methods.

Published in the topical collection Recent Trends in Solid-Phase

Extraction for Environmental, Food and Biological Sample

Preparation with guest editors Anna Laura Capriotti, Giorgia La

Barbera and Susy Piovesana.

* Susy Piovesana

susy.piovesana@uniroma1.it

1 Department ofChemistry, Università di Roma “La

Sapienza”, Piazzale Aldo Moro 5, 00185Rome, Italy

1252 A.L.Capriotti et al.

1 3

Graphical Abstract

Keywords Magnetic solid-phase extraction· Sample preparation· Magnetic materials· Sample clean-up· Pre-

concentration

Abbreviations

ACN Acetonitrile

NTf2 Bis(triﬂuoromethylsulfonyl)imide

CHG-AFS Chemical hydride generation-atomic

ﬂuorescence spectrometry

COFs Covalent organic frameworks

DLLME Dispersive liquid–liquid

microextraction

EtOH Ethanol

EGDMA Ethylene glycol dimethacrylate

IMAC Immobilized metal aﬃnity

chromatography

NPs Magnetic nanoparticles

MSPE Magnetic solid-phase extraction

MOFs Metal organic frameworks

MOAC Metal oxide aﬃnity chromatography

MeOH Methanol

MWCNTs Multi-walled carbon nanotubes

PDA Polydopamine

PTh-DBSNa/Fe3O4 Polythiophene-sodium dodecyl ben-

zene sulfonate/Fe3O4

QuEChERS Quick, Easy, Cheap, Eﬀective, Rug-

ged and Safe

[VAFMIM]Cl 1-Vinyl-3-(2-amino-2-oxoethyl)

imidazolium chloride

Introduction

Sample preparation, also called pre-treatment, has an impor-

tant role in any analytical method and becomes fundamental

for the analysis of complex matrices, i.e., food, biologic and

environmental samples. Sample preparation allows enrich-

ing and isolating the target analytes, thus reducing matrix

eﬀects and interfering compounds. As such, sample prepa-

ration is unavoidable for trace analysis. Sample preparation

based on the interaction with a solid phase is probably the

most common approach in any analytical method and com-

prises an array of strategies that diﬀer based on the nature

of the employed stationary phase [1]. Among the diﬀerent

approaches in SPE, the use of magnetizable materials has

been becoming increasingly important and popular because

of the advantages of this format over conventional packed

SPE. Magnetic solid-phase extraction (MSPE) was devel-

oped by Šafaříková and Šafařík in Ref. [2] and consists of

a magnetic material dispersed into a sample solution and

easily and swiftly recovered by application of a magnetic

ﬁeld. MSPE allows bypassing common issues with conven-

tional packed SPE, such as sorbent packing problems, high

back pressure or clogging [3]. In a typical MSPE protocol,

magnetic nanoparticles (NPs) are incubated with a liquid

sample (the unprocessed sample, diluted liquid sample or

extract) for a time ranging between few minutes to hours,

to allow the adsorption on the material of the target ana-

lytes and equilibrium (however, adsorption experiments are

often empirical and do not aim at elucidating the type of

mechanism involved) (Fig.1). The NPs are recovered from

the bulk solution by application of a magnet, although other

1253Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

approaches are possible as well, such as centrifugation or

ﬁltration. After recovery of the magnetic material and a pos-

sible washing step to remove weakly bound species, the ana-

lytes are ﬁnally eluted. A proper solvent or solvent mixture

is optimized to desorb the analytes from the magnetic NPs

and recover them for further processing. HPLC coupled to

UV-Vis spectroscopy or MS is often the preferred analysis

approach (Fig.1).

Diﬀerent magnetic materials have been developed since

the introduction of MSPE in 1999 (Fig.2).

The analytical applications to MSPE have been recently

reviewed for graphene composites, polymers, carbon nano-

tubes, ionic liquids, deep eutectic solvents, metal organic

frameworks (MOFs), boronate aﬃnity materials, host-guest

molecular recognition by supramolecules, MIPs, aptamers

[4], polydopamine (PDA) [5] and MIPs and MIP-carbon

composites [6]. Covalent organic frameworks (COFs) are

materials made up of light elements (H, O, C, N, B, Si) con-

nected with organic monomers via strong covalent bonds, in

a novel type of ordered crystalline porous polymers. COFs

are characterized by a low crystal density, large speciﬁc

surface area, highly regular porosity, tunable pore size and

excellent thermal stability. COFs have been employed in sev-

eral technologic applications, including sample preparation

in magnetic fashion [1]. MOFs represent a recent develop-

ment of nanoporous materials: they are hybrid porous mate-

rials made up by coordination bonds between metal clusters

and organic ligands. They have attracting features, such as

the ultrahigh speciﬁc surface area (typically range from

1000 to 10,000m2g−1), well-deﬁned pore structure, tunable

chemistry and high thermal stability, and their application as

sorbents for biomolecules was recently reviewed [7].

In this context, the aim of this minireview is providing an

overview of the latest developments in sample preparation

Fig. 1 Graphical representation of the main steps involved in an MSPE protocol

Fig. 2 Development of MSPE

since the introduction in 1999.

Milestones antecedent to the

deﬁnition of MSPE but concep-

tually related are also shown in

shaded colours

1254 A.L.Capriotti et al.

1 3

by MSPE. Some selected applications to diﬀerent samples,

from food to biologic and environmental samples, were

selected among those most recently reported in the litera-

ture. The overview is not a comprehensive one and aims at

providing the recent trends in the application of magnetic

materials for SPE.

Investigation ofContaminants inFood,

Environmental andBiologic Matrices

Magnetic Solid‑phase Extraction ofDrugs

MSPE of drugs was reviewed in 2016 [8]. Since then, sev-

eral other examples have been described in the literature.

Magnetic graphene composites and derived material have

been recently reviewed [4], and include applications to

antibiotics (sulfonamides, ﬂuoroquinolones, tetracycline,

cephalosporins), analgesics and anti-inﬂammatory drugs

(naproxen, diclofenac, ibuprofen) in different matrices

(wastewater, food and biologic ﬂuids). Recently, a magnetic

graphene oxide composite with β-cyclodextrin was devel-

oped for investigation of carbamazepine, phenytoin and

diazepam in plasma samples. The method was coupled with

HPLC–DAD (Table1) [9]. Non-graphene magnetic carbon

composite materials were recently used for the enrichment

of the antiepileptic drugs oxcarbazepine, phenytoin, and

carbamazepine from human plasma, urine and cerebrospi-

nal ﬂuid. The composite was prepared by functionalization

with multi-walled carbon nanotubes (MWCNTs) of Fe3O4

NPs covered with PDA (Table1). The MSPE method was

coupled with HPLC–DAD analysis [10].

Traditional coated magnetic NPs were used in recent

MSPE applications. Polythiophene-sodium dodecyl ben-

zene sulfonate/Fe3O4 (PTh-DBSNa/Fe3O4) was used for the

enrichment of lorazepam and clonazepam from biologic ﬂu-

ids. The MSPE was coupled with dispersive liquid–liquid

microextraction (DLLME) clean-up by a deep eutectic sol-

vent and HPLC–UV detection. The method resulted in a fast

procedure, and was competitive with a previously published

work (Table1) [11].

Surfactant-coated Fe3O4@decanoic acid NPs were

recently employed for the enrichment of both hydropho-

bic and hydrophilic drugs from human urine. MSPE was

combined with DLLME clean-up and GC-FID analysis. A

method was developed for urine samples using model com-

pounds, i.e., venlafaxine, as a hydrophilic model drug and

desipramine and clomipramine as hydrophobic model drugs

(Table1) [12].

MIPs were recently reviewed in their application to analy-

sis of drugs in both environmental samples and food and bio-

logic samples [13]. For further reading on this topic, there is

also a recent review on MIPs for the extraction of antibiotics

in milk, which features MSPE applications to penicillin V,

sulfamethazine, oxacillin, oﬂoxacin, ciproﬂoxacin and lome-

ﬂoxacin, oxytetracycline, tetracycline, chlortetracycline,

doxycycline and sulfamethoxazole. Finally, magnetic MIPs

were employed for the investigation of macrolide antibiotics

in food and hexamethylenetetramine in milk [6].

Hybrid materials conjugating carbon supports with

polymers have been described in drug analysis. Recently, a

magnetic reduced graphene oxide functionalized with poly-

ethyleneimine was used for the enrichment of trace polar

non-steroidal anti-inﬂammatory drugs in diﬀerent water

matrices. Fe3O4 was covered with polyethyleneimine by a

one-pot hydrothermal approach and then the ﬁnal composite

was fabricated by simple self-assembly between the posi-

tively charged polyethyleneimine and the negatively charged

graphene oxide sheets via electrostatic interaction followed

by chemical reduction of graphene oxide. The incorporation

of reduced graphene oxide allowed increasing the aﬃnity

for polar drugs. A method with HPLC–DAD detection was

developed (Table1) [14].

Carbon materials conjugated with MIPs have also been

employed for MSPE of drugs. For instance, in a recent

report, an MWCNT-based magnetic MIP was synthesized

and applied for the selective extraction and pre-concen-

tration of sotalol in biologic ﬂuid samples (human urine

and plasma) by ultrasonic-assisted dispersive solid-phase

microextraction. The material was prepared by MIP syn-

thesis in presence of carboxyl-modiﬁed MWCNTs, Fe3O4

NPs, the monomer (acrylamide) and cross-linker (ethylene

glycol dimethacrylate, EGDMA). A method was optimized

for recovery of the target analyte and HPLC–UV detection

(Table1) [15].

Magnetic NPs superﬁcially coated with polymers are a

traditional approach in the preparation of magnetic mate-

rials for MSPE, and the approach was still used in recent

works. For instance, Fe3O4 NPs, coated by grafting copoly-

merization with poly (N-vinylcaprolactam) and 3-allyloxy-

1,2-propanediol, were used for the pre-concentration of the

antibiotic cefexime in human plasma and urine samples. The

method was optimized and coupled with HPLC–DAD. The

polymer used for coating is a thermo-sensitive polymer, with

potential application in drug delivery. Indeed, during method

optimization a temperature-dependent interaction with the

analyte was observed; in fact, a temperature increase from

15 to 32°C reduced the hydrophobic features of the thermo-

sensitive polymer and, unsurprisingly, aﬀected the loading

of hydrophilic drugs, which was also decreased (Table1)

[16].

MOF magnetic NPs were used for the enrichment of

drugs, including sulfonamides in shrimp, chicken and pork

samples [17]. MOFs were recently employed in combina-

tion with HPLC–MS for the investigation of seven non-

steroidal anti-inﬂammatory drugs (meloxicam, carprofen,

1255Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

Table 1 Summary of MSPE methods discussed in the cited papers

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Magnetic gra-

phene oxide-

β-cyclodextrin

polymer

Phenytoin,

carbamazepine,

diazepam

Plasma (deprotein-

ized)

25mgM; 20min

incubation;

elution: 1mL

MeOH; evapora-

tion

HPLC–DAD 11.89–

47.10ngmL−1 39.62–

157.01ngmL−1 ≤ 5.82% 77.44–100.93% [9]

Fe3O4@PDA–

MWCNTs

Oxcarbazepine,

phenytoin, carba-

mazepine

Human plasma,

urine, and cer-

ebrospinal ﬂuid

15mgM in 5mL

sample (pH 6);

1.5min incuba-

tion; elution:

2.5mL MeOH;

evaporation

HPLC–DAD 0.4–3.1ngmL−1 –≤ 8.2% 92.8–96.5% [10]

Polythiophene-

sodium dodecyl

benzene sulfonate/

Fe3O4

Clonazepam,

lorazepam

Human urine,

plasma (depro-

teinized)

17mgM in 8mL

sample (pH 7);

elution: 245 µL

MeOH; DLLE

with deep eutec-

tic solvent

HPLC–UV 12–15ngmL−1;

5–7ngmL−1 40–45ngmL−1;

18–25ngmL−1 ≤ 6.9% 49–52%, 38–39% [11]

Fe3O4@decanoic

acid

Venlafaxine,

desipramine,

clomipramine

Human urine 6mgM in urine/

water, 1:2 (v/v,

pH 10); 15min

incubation;

elution: 1mL

0.03mol L−1

HCl in ACN;

DLLME with 20

µL chloroben-

zene;

GC-FID 0.0025–

0.004µgmL−1 –≤ 13.7% 58.0–82.4% [12]

Fe3O4@polyethyl-

eneimine@reduced

graphene oxide

Diclofenac, nap-

roxen, ketoprofen

Groundwater, tap

and river water

5mgM in 10mL

sample (pH 4);

5min incuba-

tion; elution:

200 µL MeOH/

NH3 (19:1, v/v):

evaporation

HPLC–DAD 0.2µg L−1 1 μg L−1 ≤ 8.75% 91.20–101.13% [14]

Magnetic MWCNT-

MIP (sotalol

imprinted

poly(acrylamide-

co-EGDMA)

Sotalol Human urine,

plasma

15mgM in sample

(pH 7); 22min

incubation;

washing: water;

elution: 10mL

MeOH/acetic

acid (9:1, v/v);

evaporation

HPLC–UV 0.31ngmL−1 –≤ 4.5% 94.6–102.5% [15]

1256 A.L.Capriotti et al.

1 3

Table 1 (continued)

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Fe3O4@poly

(N-vinylcaprolac-

tam-co-3-allyloxy-

1,2-propanediol)

Cefexime Human plasma,

urine

10mgM in 20mL

sample (pH 5);

5min incubation;

elution: 250 µL

MeOH/acetic

acid (97:3, v/v)

HPLC–DAD 4.5 × 10−4 μgmL−1 –≤ 4.11% 71–89% [16]

Fe3O4@MIL-

100(Fe)

7 non-steroidal

anti-inﬂamma-

tory drugs

Urban and

pharmaceutical

wastewater, lake,

ﬁshpond feed

water

25mgM in 50mL

sample (pH 5);

45min incuba-

tion; elution:

1mL ACN/

HCOOH (99:1,

v/v); evaporation

HPLC–MS 0.02–0.09µg L−1 0.06–0.30µg L−1 ≤ 9.6% 75.2–105.2% [18]

PDA dendrimer

functionalized with

Fe3O4

Ibuprofen,

diclofenac, nap-

roxen

Water 25mgM in 50mL

sample (pH 7);

5min incubation;

elution: 1mL

MeOH/acetic

acid (95:5, v/v);

evaporation

HPLC–UV 0.05–0.08ngmL−1 0.15–0.20ngmL−1 ≤ 7.3 93.6–98.9% [19]

Fe3O4@reduced

graphene oxide

Phthalates Water 60mgM in 25mL

sample (pH 6);

1min incubation;

N2 for drying;

elution: 4mL

CH2Cl2; evapora-

tion

HPLC–MS – 6–178ng L−1 ≤ 20% 70–120% [20]

Magnetic graphitized

carbon black

10 UV ﬁlters

(benzophenones,

p-aminobenzo-

ates)

Lake, river water 100mgM in

50mL sample

(pH 7); 30min

incubation;

elution: 10mL

ACN with 0.05%

HCOOH; evapo-

ration

HPLC–MS 1–5ng L−1 2–10ng L−1 ≤ 15% 85–114% [21]

Hollow porous

NiMn2O4 nano-

spheres-decorated

cellulose-based

carbon ﬁbres

6 bisphenol ana-

logs

Water, plastic food

containers

30mgM in

200mL sample;

30min incuba-

tion; elution:

5mL MeOH;

evaporation

HPLC–UV 0.56–0.83ngmL−1 1.85–2.76ngmL−1 ≤ 4.2% 84.3–103.5% [22]

1257Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

Table 1 (continued)

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Fe3O4@MIP (tri-

closan imprinted

poly(methacrylate-

co-EGDMA))

Triclosan Water 8mgM in 15mL

sample (pH

3); incubation

30min, 35°C;

HPLC–UV 0.20µg L−1 0.66µg L−1 ≤ 4.5% 89.5–108.4% [23]

Fe3O4@PDA 4 estrogens, 6

mycoestrogens, 8

phytoestrogens

Lake, river water 90mgM in 25mL

sample; 15min

incubation;

elution: 5mL

MeOH (2 ×);

evaporation

HPLC–MS 0.0003–0.01μg

L−1 0.0028–0.10μg

L−1 ≤ 22% 72–102% [24]

Covalent triazine

framework/Fe2O3

7 phenolic pollut-

ants

Water 40mgM in 25mL

sample; 30min

incubation; elu-

tion: 2mL ACN

(× 3)

HPLC–UV 0.09–0.53ngmL−1 –≤ 9.9% 84–97.7% [25]

Magnetic

MWCNT@PDA/

zeolitic imida-

zolate framework-8

composite (MMP/

ZIF-8)

5 triazole fungi-

cides

Water 10mgM in 5mL

sample; 2min

incubation;

elution: 0.5mL

acetone (3 ×);

evaporation

GC–MS 0.08–0.27µg L−1 –≤ 9.65% 83.4–98.3% [26]

M-M-ZIF-67 9 organochlorine

pesticides

Water 6mgM in 5mL

sample; 20min

incubation; elu-

tion: 2mL ACN

(2 ×); evapora-

tion

GC–MS 0.07–1.03µg L−1 –≤ 8.5% 74.9–116.3% [27]

Fe3O4@SiO2@MIP

(ametryn imprinted

poly(2-vinylpyri-

dine-co-EGDMA))

Ametryn Fruit, vegetables

(extracts)

1mgM in 1mL

sample; 2h incu-

bation; elution:

1mL MeOH

HPLC–UV 25nmol L−1 82nmol L−1 – 100% [29]

Fe3O4@SiO2@C8 9 pesticides Fruit and vegeta-

bles juices

100mgM in

30mL sample

with 20% NaCl

(w/v); extrac-

tion by gravity

(4 ×); elution:

1mL MeOH;

DLLME with

1,1,2-trichloro-

ethane

GC-FID 0.03–0.09µg L−1 0.09–0.29µg L−1 ≤ 8% 64–82% [30]

1258 A.L.Capriotti et al.

1 3

Table 1 (continued)

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Fe3O4/triphenylphos-

phine and benzene

knitting aromatic

polymer

Metoxuron, monu-

ron, chlortoluron,

monolinuron,

buturon

Juice, milk and

soymilk

25mgM in

100mL sample;

20min incuba-

tion; elution:

0.2mL ACN

HPLC–UV 0.05–0.30ngmL−1 0.17–1.00ng·mL−1 ≤ 8.4% 91.8–106.5% [31]

Magnetic activated

carbon

16 PHAs Waters, wastewa-

ter, sewage, soil

25mgM in

500mL sample;

30min incuba-

tion; elution:

1.55mL ACN/

toluene (96.7:3.3,

v/v); DLLME

GC–MS 0.1–0.5ngkg−1 0.4–0.8ngkg−1 ≤ 8.66% 74.8–102.6% [32]

Fe3O4@SiO2@C60 16 PAHs Tea 40mgM in

100mL sample;

6min incubation;

elution: 0.5mL

hexane and

0.5mL acetone

GC–MS 0.8–14.3ng L−1 2.6–47.6ng L−1 ≤ 10.6% 98.5–106.7% [33]

Magnetic graphene

oxide@polystirene

4 PAHs Water 15mgM in 20mL

sample with

20% NaCl (w/v);

5min incubation;

elution: 5mL

hexane; evapora-

tion

GC-FID 3–10pgmL−1 –≤ 7.4% 69.5–88.7% [34]

Magnetic graphene/

MWCNTs/PDA

16 PAHs Pond water 20mgM in 50mL

sample; 5min

incubation;

elution: 1.5mL

ACN with

100mg anhy-

drous Na2SO4;

evaporation

GC–MS 0.1–3.0ng L−1 0.3–9.0ng L−1 ≤ 9.6% 62.2–95.4% [35]

Fe3O4@mSiO2-Ph-

p-toluenesulfonic

acid

15 PAHs Soil (extract) 15mgM; 20min

incubation;

elution: 7mL

CH2Cl2/acetone,

1:1, v/v); evapo-

ration

GC–MS 0.07–0.41 ng g−1 0.24–1.37 ng g−1 ≤ 11.23% 86.85–110.01% [36]

1259Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

Table 1 (continued)

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Fe3O4@polyani-

line@ dicationic

ionic liquid-NTf2

5 PAHs Water, sludge, soil 15mgM in 30mL

sample; 20min

incubation;

elution: 1.5mL

ACN; evapora-

tion

GC–MS 0.0008–0.2086µg

L−1 0.0024–0.6320µg

L−1 ≤ 5.6% 80.2%–111.9% [37]

Fe3O4@(chitosan-

Se)2

Pb(II), Cd(II),

Ni(II), Cu(II)

Sausage, drinking

water, waste-

water

8mgM (with

100mg Na2CO3

and 100mg citric

acid) in 10mL

sample (pH 6);

eﬀervescence

(30s); elution:

300 μL 3mol

L−1 HNO3

Microﬂame AAS 0.15–2.0ngmL−1 0.7–6.3ngmL−1 ≤ 4.1% 96–103% [40]

Fe3O4@catechol Cd(II), Co(II),

Cr(III), Cu(II),

Mn(II), Ni(II),

Pb(II)

Well and mineral

water, apples,

pomegranate,

watermelon, kiwi

70mgM in 60mL

sample (pH 9);

9min incuba-

tion; elution: 250

µL 0.3mol L−1

EDTA

ICP-OES 0.2–0.9 μg L−1 –≤ 6.6% 95–98% [41]

Fe3O4@MnO2As(III) Water (river, lake,

spring, rain)

10mgM in 50mL

sample; 30min

incubation;

washing: water;

elution: 5mL

0.5mol L−1 HCl

CHG-AFS 2.9 ng L−1 –≤ 4.8% 85.6–115% [42]

C. micaceus biosorb-

ent

Co(II), Hg(II) Potato, cabbage,

ketchup, green

pepper, meat,

tuna, chicken,

milk, tap,

mineral and river

water

100mgM (packed

in cartridge),

30mL sample;

washing: water;

elution: 5mL

1mol L−1 HCl

ICP-OES 0.04–

0.017ng mL−1 0.056–

0.12ngmL−1 ≤ 3.7% 98.5–99.1% [43]

Magnetic nanogra-

phene

Zearalenone Corn (extract) 20mgM in 2mL

sample; 15min

incubation;

elution: 1mL

MeOH with 0.5%

formic acid

HPLC-ﬂuores-

cence

0.5mg L−1 0.13mg L−1 < 4% 79.3–80.6% [45]

1260 A.L.Capriotti et al.

1 3

Table 1 (continued)

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Magnetic graphitized

carbon black

6 mycoestrogens Cow milk 100mgM in

48mL sample;

30min incuba-

tion; elution:

10mL CH2Cl2/

MeOH (80:20,

v/v); evaporation

HPLC–MS 3–9ng L−1 8–15ng L−1 ≤ 22% 93–107% [46]

Magnetic graphitized

carbon black

4 aﬂatoxins, OTA,

ZEN

Corn meal, durum

wheat ﬂour

(extracts)

50mgM in

25mL; 30min

incubation;

washing: water;

elution: 5mL

CH2Cl2/MeOH

(80:20, v/v) with

0.2% formic

acid; evaporation

HPLC–MS 0.05–1.0µgkg−1 0.05–2.2µgkg−1 ≤ 20% 63–89% [47]

Fe3O4-MWCNT-

NH2

Aﬂatoxin B1,

zearalenone

Wheat ﬂour

(extract)

6mgM in 3mL

sample (pH 5.5);

25min incuba-

tion; elution:

0.2mL acetone

(3 ×)

HPLC–DAD 0.15, 0.24ngg−1 0.52, 0.83ngg−1 ≤ 6.6% 88.8–96.0% [48]

Fe3O4@MIP

(deoxynivale-

nol imprinted

poly(methacrylic

acid-co-divinylben-

zene))

6 mycotoxins Rice (extract) 30mgM in 10mL

sample; elution:

1mL MeOH/

NH3 (98:2, v/v);

evaporation

HPLC–MS 0.001–

0.003μg·kg−1 0.003–

0.01μgkg−1 ≤ 7.3% 6.3–103.1% [50]

Co3O4@C@

MIP (3-cou-

marincarboxy-

lateas imprinted

poly(methacrylic

acid-co-EGDMA))

5 aﬂatoxins Corn 80mgM; 10min

incubation;

washing: 3mL

water; elution:

1.2mL ACN/

water (60:40,

v/v)

HPLC–MS 0.05–0.07ngmL−1 0.15–0.22ngmL−1 ≤ 5.1% 75.1–99.4% [51]

3D hollow porous

CdFe2O4 micro-

spheres

Acid Red, Congo

Red, Sunset

Yellow

sport drinks, jelly

and fruit ﬂavored

candies

40mgM in

150mL sample;

40min incuba-

tion; elution:

4mL EtOH/

Na3PO4 (3:2,

v/v); evaporation

HPLC–UV 0.54–1.00ngmL−1 1.79–3.35ngmL−1 ≤ 4.1% 87.0–100.7% [52]

1261Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

Table 1 (continued)

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Copper phthalocya-

nine dyed acrylic

felt

Crystal violet,

Safranin O

Water 1 × 1 textile square

in 100mL

sample (pH 7);

3h incubation;

elution: 2mL

MeOH

UV–VIS spectros-

copy

2.66mg L−1;

2.17mg L−1 8.87mg L−1;

7.23mg L−1 – 50–80% [53]

Chitosan on mag-

netic textile

Blue fountain ink

dye (acid blue

93)

Water (standard

solution or paper

extract)

1 × 1 textile square

in 300mL

sample (pH 7);

4h incubation;

elution: 3mL

0.01mol L−1

NaOH

UV–VIS spectros-

copy

– – – – [54]

Chitosan on mag-

netic textile

Tartrazine, azoru-

bine, Indigo

carmine

Dyes solutions 2 × 2 textile square

in 100mL

sample; 2h incu-

bation; washing:

water

Image analysis ~20 µg L−1 –≤ 15% – [55]

Poly(methyl meth-

acrylate)@gra-

phene oxide/Fe3O4

nanocomposite

Aniline, N,N-

dimethylaniline,

o-toluidine, and

3-chloroaniline

Water 25mgM in 30mL

sample (pH 6);

5min incubation;

elution: 150 µL

CH2Cl2

GC-FID 2 and 6pgmL−1 –≤ 8.6% 90.3–99.0% [56]

Fe3O4@PEG@MIP

(propanamide

imprinted chitosan)

Acrylamide Biscuits (extract) 40 mgM in 15mL

sample (pH 5);

20min incuba-

tion; elution:

2mL MeOH/

NH3 (90:10, v/v);

evaporation

HPLC–UV 1.3µgkg−1 4.4µgkg−1 ≤ 4.1% 86.0–98.3% [57]

Fe3O4@SiO2/

graphene oxide/β-

cyclodextrin/ionic

liquid

7 plant growth

regulators

Vegetables

(extract)

60mgM in 5mL

sample (pH 2);

5min incuba-

tion; elution:

2mL MeOH/

NH3 (95:5, v/v);

evaporation

HPLC–MS 0.01–0.18 μgkg−1 0.03–0.58 μgkg−1 ≤ 10.4% 80.4–108.0% [58]

Fe3O4-MWCNTs 48 veterinary

drugs, 13

pesticides, 13

mycotoxins

Egg (QuEChERS

extract)

15mg in 2mL

sample; 1min

incubation;

supernatant fur-

ther processed

HPLC–MS – 0.1–17.3µg kg−1 ≤ 20% 60.5–114.6% [59]

1262 A.L.Capriotti et al.

1 3

Table 1 (continued)

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Fe3O4@SiO2@

PAF-6

Phenol, 2,4,6-trini-

trophenol, naph-

thalene, naphthol,

bisphenol A,

2,4-dichlorophe-

nol and 3-nitro-

chlorobenzene

Water 60mgM in

300mL sample

(pH 6); 5min

incubation;

elution: 2.5mL

ACN (2 ×);

evaporation

HPLC–UV/ﬂuo-

rescence

0.08–5.02 ngmL−1 –≤ 9.1% 84.0–94.0% [60]

Fe3O4@SiO2@

graphene oxide

4 cytokinins Tobacco leaves

(extract)

20mgM in 4mL

sample (pH 5);

20min incuba-

tion; elution:

2mL water/ACN

(20:80, v/v, 3 ×);

evaporation

HPLC–MS 93–120pgmL−1 –≤ 12.5 82.6–97.3% [74]

Fe3O4@MIP

(6-mercaptopu-

rine imprinted

poly(methacrylate-

co-EGDMA))

6-Mercaptopurine,

thioguanine

Human plasma

(deproteinized)

100mgM in 5mL

sample (pH 5);

30min incuba-

tion; washing:

2mL EtOH;

elution: 2mL

MeOH/NH3

(95:5, v/v)

HPLC–MS 0.382,

0.333μgmL−1 1.158,

1.009μgmL−1 ≤ 1.778 85.94–103.03% [75]

Fe3O4@NH2 (CB

[6]) NH2

7 salvianolic acids Danshen (extract) 1mgM in 1mL

sample; 20min

incubation;

elution: 1mL

MeOH/acetic

acid (60:20, v/v)

HPLC–DAD 12.50ngmL−1 53.8ngmL−1 ≤ 9.7% 5.1% to 106.5% [76]

Fe3O4@SiO2@

MIP (cheleryth-

rine imprinted

poly(methacrylate-

co-EGDMA))

Chelerythrine Plant (extract) 20mgM in 5mL

extract; 60min

incubation; elu-

tion with 2mL

MeOH/acetic

acid, 9:1 (v/v);

evaporation

HPLC–UV – – – – [77]

Porous magnetic

β-cyclodextrin

polymer

Tumor markers

(p-hydroxy-

benzoic acid,

p-cresol)

Human urine 20mgM in

10mL; 20min

incubation; elu-

tion: MeOH/BR

buﬀer pH 10, 9:1

(v/v)

HPLC–DAD 1.016, 5.714μg

L−1 –≤ 3.19 88.82–104.34% [78]

1263Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

Table 1 (continued)

Material (M) Analytes Sample MSPE procedure Detection LOD LOQ RSD (%) Recovery (%) References

Fe3O4@chitosan@

MIP with deep

eutectic solvent

imprinted with

catechin

(+)-Catechin,

(−)-epicatechin,

(−)-epigallocat-

echin gallate

Black tea (extract) 100mgM in 1mL

sample; 30min

incubation;

washing: 2mL

water; elution

1mL MeOH/

acetic acid, 9:1

(v/v)

HPLC–UV 0.15–0.50µgmL−1 0.50–1.50µgmL−1 ≤ 6.84% 88.3–98.1% [79]

Fe3O4@SiO2@MIP

with ternary deep

eutectic solvent

Theophylline,

theobromine,

(+)-catechin

hydrate, caﬀeic

acid

Green tea (extract) 200mgM in

100mL sample;

30min incuba-

tion; elution:

2.5mL MeOH

(2 ×)

HPLC–UV – – – 91.82, 92.13,

89.96, 90.73%

[80]

Fe3O4@SiO2@

carboxymethyl-β-

cyclodextrin

Paraquat, diquat Water (river, reser-

voir, tap)

100mgM in

150mL sample

(pH 12); 10min

incubation;

elution: 100 µL

0.3mol L−1 HCl

(2 ×)

HPLC–DAD 0.8µg L−1; 0.9µg

L−1 – < 9.6% 70.2–100.0% [85]

Fe3O4@graphitic

carbon submicro-

cubes

Dimethyl phtha-

late, diethyl

phthalate, benzyl

butyl phthalate,

dibutyl phthalate,

dicyclohexyl

phthalate

Beverages, plastic

(bottles, extract)

25mgM in 25mL

sample; 10min

incubation; 400

µL ACN (3 ×)

HPLC–UV 0.09–0.28μg

L−1 (beverage)

0.01–0.03μgg−1

(plastic)

–≤ 8.8% 80.0–112.8% [88]

Magnetic carbon

material from

pomelo peels

8 parabens, 7 ﬂuo-

roquinolones

Water (lake, river,

tap, waste, res-

ervoir)

50mgM in

100mL sample

(pH 3); 11min

incubation;

elution: 0.5mL

ACN

HPLC–DAD 0.011–0.053µg

L−1 0.037–1.53 < 10% 77–116% [89]

Magnetic hal-

loysite nanotubes/

[C16mimBr] hem-

imicelles

Methyl red, methyl

orange

Water (tap, lake) 60mgM in

200mL sample

(pH 7); 7min

incubation¸

washing: water;

elution: 1mL

MeOH (2 ×)

HPLC–DAD 0.042µg L−1;

0.050µg L−1 0.12µg L−1;

0.16µg L−1 < 5.4% 85–93% [87]

The material (M), target analytes, MSPE procedure, detection and main analytical ﬁgures are reported for every reference

ref reference, MeOH methanol, ACN acetonitrile, CHG-AFS chemical hydride generation-atomic ﬂuorescence spectrometry, EtOH ethanol)

1264 A.L.Capriotti et al.

1 3

indometacin, tolfenamic acid, diclofenac, naproxen and

mefenamic acid) in environmental water samples. The mate-

rial [a core–shell Fe3O4@MIL-100(Fe)] contained MIL-

100(Fe), which is a representative MOF constituted by a

mixed tetrahedron Fe(III) and trimesic acid (Table1) [18].

Polyamidoamine dendrimer functionalized with Fe3O4

was recently used for extraction of three non-steroidal anti-

inﬂammatory drugs (ibuprofen, diclofenac and naproxen)

in environmental water. A good general performance of

the method could be accomplished in combination with

HPLC–UV detection (Table1) [19].

Magnetic Solid‑phase Extraction

ofEndocrine‑disrupting Compounds

Magnetic graphene composites and derived materials have

been recently reviewed for MSPE of endocrine-disrupting

compounds [4] and include applications to phthalates, bis-

phenols and phenols in water and fruit juice. More recent

MSPE applications, which exploit graphene-related mag-

netic materials, include the use of Fe3O4 NPs coated with

reduced-graphene oxide as sorbent for the extraction of 14

phthalic acid esters (i.e., benzylbutyl phthalate,bis-2-n-

butoxyethyl phthalate, dibutyl phthalate, diisobutyl phtha-

late, dicyclohexylphthalate, bis-2-ethoxyethyl phthalate,

diisodecyl phthalate, diisononyl phthalate, bis-isopentyl

phthalate, bis-(2-methoxyethyl) phthalate, dimethyl phtha-

late, di-n-octyl phthalate, bis-n-pentyl phthalate, dipropyl

phthalate) from water samples (mineral, pond and waste-

water) [20]. The method was optimized and coupled with

HPLC–MS (Table1).

Other carbon materials diﬀerent from graphene have

been used for MSPE of endocrine-disrupting chemicals.

For instance, magnetized graphitized carbon black was used

for enrichment of ten UV ﬁlters belonging to the chemi-

cal classes of benzophenones (4,4′-dihydroxybenzophe-

none, 4-hydroxy-2-methoxybenzophenone-5-sulfonic acid,

2,2′,4,4′-tetrahydroxybenzophenone, 4-hydroxybenzophe-

none, 2,4-dihydroxybenzophenone, 2,2-dihydroxy-4-meth-

oxybenzophenone, 2-hydroxy-4-methoxy-benzophenone)

and p-aminobenzoates [p-aminobenzoic acid, ethyl 4-amin-

obenzoate, 2-ethylhexyl 4-(dimethylamino)benzoate] from

water. A method coupled with HPLC–MS was developed

and ﬁnally applied to environmental surface water samples

(Table1) [21]. Carbon ﬁbers magnetized with inexpensive

hollow porous NiMn2O4 nanospheres were used for the

extraction of six bisphenol analogs [2,2-bis (4-hydroxyphe-

nyl) propane, 4,4′-dihydroxy diphenylmethane, 4,4′-(1-phe-

nylethylidene) bisphenol, 4,4′-thiodiphenol, 4,4′-isopro-

pylidenedi-o-cresol, 4,4-dihydroxydiphenyl sulfone] from

drinking water, plastic food containers and sea water sam-

ples. The material was produced by a green hydrothermal

synthesis and calcination of recyclable cotton wool as a

carbon ﬁber source. The material was highly porous with a

large surface area, which improved the binding of the target

analytes. A method was optimized and coupled with HPLC

analysis (Table1) [22].

Among other materials used for endocrine-disrupting

chemical MSPE, there are magnetic COFs, which were

used to enrich estrogens in urine, bisphenols in human

serum and aqueous solution and perﬂuorinated compounds

in water [1], and magnetic MIPs, which were applied to

diethylstilbestrol, hexestrol, dienestrol and bisphenol A in

water, orange juice and milk and phthalate esters in bever-

age and environmental water samples [6]. MIPs supported

on magnetic NPs were used for MSPE of triclosan, an anti-

microbial agent used in personal care products. Triclosan

was used as template, methacrylic acid as functional mono-

mer and EGDMA as cross-linker. The MSPE method was

coupled with HPLC–UV detection. The material showed a

good selectivity for analog compounds, except triclocarban

(Table1) [23].

Dopamine can be polymerized under mild conditions to

produce PDA, a very versatile material characterized by high

hydrophilicity and biocompatibility; moreover, PDA can be

produced on a variety of surfaces because of the special

adhesion properties that it displays. PDA chemistry was also

exploited in the MSPE of endocrine-disrupting compounds

for enrichment of phenols in environmental waters. Fe3O4@

PDA-MIP was used for the enrichment of bisphenol A,

tetrabromobisphenol A, 2,4,6-tribromophenol and (S)-1,1′-

bi-2-naphthol and diethylstilbestrol [5]. Fe3O4@PDA was

used for isolation and enrichment of 17 compounds with

estrogenic activity (4 estrogens, 6 mycoestrogens and 7

phytoestrogens, including the estrogenic metabolite equal)

in surface water samples by a multiresidue MSPE coupled

with HPLC–MS analysis (Table1) [24]. Hybrid composites

of PDA with magnetic graphene were applied for MSPE of

phthalates [5].

Other recent applications of MSPE of endocrine-dis-

rupting chemicals reported in the literature include a mag-

netic triazine material employed for investigation of seven

phenolic pollutants (phenol, 4-nitrophenol, 2-nitrophenol,

2-chlorophenol, 4-chloro-3-methylphenol, 2,4-dichloro-

phenol and 2,4,6-trichlorophenol) in environmental water

samples (tap, spring and pond water samples, Table1) [25].

Magnetic Solid‑phase Extraction ofPesticides

Magnetic graphene composites and derived materials have

been recently reviewed in MSPE of peptides [4] and are

mainly applied to organophosphorous pesticides, but also

carbamate pesticides, pyretroid pesticides, triazole fungi-

cides, triazine herbicides and phenoxy acid herbicides in dif-

ferent matrices (fruit juices, water, milk, vegetables). Other

carbon materials were exploited in composite production. A

1265Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

novel magnetic zinc-based zeolitic imidazolate framework

has been prepared using a magnetic MWCNT@PDA nano-

composite as the magnetic core and support, which provided

the ﬁnal material with an improved adsorption capacity. The

material was applied to ﬁve triazole fungicides (propicona-

zole, difenoconazole, epoxiconazole, fenbuconazole and

ﬂuuquinconazole) in environmental water samples (tap,

river, well, pond water) by GC–MS analysis (Table1) [26].

A magnetic nanocarbon-based composite was used for

the analysis of nine organochlorine pesticides [α-, β-, γ- and

δ-hexachlorocyclohexane, 1,1-dichloro-2,2-bis(4-chlorophe-

nyl)ethane; 2-(2-chlorophenyl)-2-(4-chlorophenyl)-1,1-di-

chloroethene, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene,

1,1,1-trichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)

ethane, and 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane]

in water (tap, river and underground water samples). Speciﬁ-

cally, magnetic carbon nanotubes were used as support for

Fe3O4 NPs and zeolitic imidazolate frameworks to produce

the derived composite (M-M-ZIF-67) (Table1) [27].

The use of MIPs in pesticide analysis was recently

reviewed. Magnetic MIPs were used for the extraction of

propoxur in apple, orange and pear, organochlorine pesti-

cides in water, diazinon in fruits, acephate in cabbage and

spinach samples, atrazine, terbuthylazine, propazine and

simazine in wheat, soybean and corn, and carbendazim

and chloroacetamides in water [28]. Moreover, examples of

MSPE applications using magnetic MIPs have been recently

discussed for the analysis of the fungicide carbendazim in

vegetables [6]. Among the recent reports of MIPs in MSPE

of pesticides, there is an ametryn-imprinted polymer used to

functionalize Fe3O4@SiO2 NPs. Computational simulation

was used to identify the best monomer for MIP production,

i.e., 2-vinylpyridine, which was used with the cross-linker

EGDMA. The method was optimized for the extraction of

ametryn from fruit and vegetable extracts (tomato, cap-

sicum, strawberry) and coupled to HPLC–UV detection

(Table1) [29].

MSPE methods using MOFs were applied to pesticide

analysis in lettuce, to pyrethroids in tea samples, to insecti-

cides in fruit and vegetables and to herbicides in rice. MOF-

derived carbon materials were used for MSPE of carbamate

pesticides in apples, herbicides in grapes and bitter gourd

and neonicotinoid insecticides in water and fatmelon [17].

Combinations of MSPE with clean-up strategies have also

been described. For instance, Fe3O4@SiO2@C8 NPs were

used for extraction and pre-concentration of nine pesticides

(diazinon, ametryn, chlorpyriphos, penconazole, haloxyfop-

R-methyl, oxadiazon, diniconazole, tebuconazole and fenaz-

aquin,) in combination with DLLME clean-up. The method

aimed at analysis of trace pesticides in fruits and vegetables

(onion, cucumber, grape and tomato), previously extracted

to produce juices. In this work, the MSPE was performed

in unconventional fashion within a narrow-bore tube. The

magnetic material was forced through the sample by grav-

ity, and then a magnet was used to move the sorbent back to

the top of the tube and repeat the process for a total of four

times (Table1) [30].

New materials and sorbents can have interesting appli-

cations in MSPE. For instance, magnetic knitting aromatic

polymers have only recently been suggested as new MSPE

sorbents and used to validate a method for ﬁve phenylurea

herbicides (metoxuron, monuron, chlortoluron, monolinu-

ron and buturon) in bottled mixed juice, milk and soymilk

samples. Knitting aromatic polymers are hyper-cross-linked

polymers that were prepared via a Friedel-Crafts reaction in

the speciﬁc case by one-pot knitting copolymerization of tri-

phenylphosphine and benzene with Fe3O4, without the need

for expensive noble metal catalysts to produce a microporous

material. The MSPE method was coupled with HPLC–UV

detection (Table1) [31]. Although the method was validated

only for the ﬁve herbicides, still the MSPE was extended

to other organic pollutants, i.e., seven PAHs (naphthalene,

ﬂuorene, acenaphthene, phenanthrene, anthracene, ﬂuoran-

thece, pyrene), four chlorophenols (2-chlorophenol, 4-chlo-

rophenol, 2,4-dichlorophenol, 2,3-dichlorophenol) and four

phthalates (diethyl phthalate, dipropyl phthalate, dibutyl

phthalate, benzyl butyl phthalate), with recoveries between

66.6 and 100.3%.

Magnetic Solid‑phase Extraction ofPolycyclic

Aromatic Hydrocarbons

Magnetic graphene composites and derived materials have

been recently reviewed for PAHs MSPE [4] and mainly

include applications to water. Other carbon materials were

also used for the purpose; for instance, commercially acti-

vated carbon was recently magnetized using the traditional

procedure developed for graphene and used for enrichment

of 16 PAHs (naphthalene, acenaphthene, acenaphthylene,

fluorene, phenanthrene, anthracene, fluoranthene, pyr-

ene, chrysene, benz[a]anthracene, benzo[b]ﬂuoranthene,

benzo[k]ﬂuoranthene, benzo[a]pyrene, indeno[1,2,3-cd]

pyrene, dibenz[a,h]anthracene, and benzo[g,h,i]perylene)

in environmental samples. The developed MSPE method

was coupled with DLLME and GC–MS analysis. Two

miscible solvents were used for elution from the magnetic

material to achieve high extraction recovery and for the sub-

sequent DLLME. The method was successfully applied to

waters, wastewater, sewage and soil samples (Table1) [32].

Another example of MSPE with a carbon magnetic material

exploits fullerene. In this case, the [60] fullerene was used

to functionalize magnetic SiO2 particles and then applied to

16 priority pollutant PAHs in tea samples. The enrichment

method was coupled with GC–MS (Table1) [33]. Other

composite materials were used for the same purpose. For

instance, PAHs were enriched by MSPE using a graphene

1266 A.L.Capriotti et al.

1 3

oxide/Fe3O4@polystirene nanocomposite (Table1) [34].

Magnetic graphene was coated with polystyrene and used for

the extraction of 4 PAHs in water. Samples were analyzed

using GC-FID. The method was applied to the analysis of

spiked water samples [34].

COFs were employed for the MSPE of PAHs, mainly

from food samples, water and soil [1].

Fe3O4@PDA has been successfully used as an MSPE

sorbent for several PAHs in environmental waters [5].

Hybrid materials containing PDA with graphene and

MWCNTs were also described for MSPE of PAHs in water.

Magnetic graphene/MWCNT assemblies were function-

alized with PDA to prepare the adsorbent. The optimized

MSPE method, coupled with GC–MS analysis, was ﬁnally

applied to 16 PAHs (naphthalene, acenaphthene, acenaph-

thylene, ﬂuorene, phenanthrene, anthracene, ﬂuoranthene,

pyrene, chrysene, benz[a]anthracene, benzo[b]ﬂuoranthene,

benzo[k]ﬂuoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyr-

ene, dibenz[a,h]anthracene and benzo[g,h,i]perylene) in a

pond water sample (Table1) [35].

Functionalized magnetic silica was recently used for

PAH enrichment from soil. Speciﬁcally, phenyl-modiﬁed

magnetic mesoporous silica was synthesized with p-tol-

uenesulfonic acid. The material, Fe3O4@mSiO2-Ph-p-tol-

uenesulfonic acid, not only showed a better aﬃnity for 15

PAHs (acenaphthylene, acenaphthene, ﬂuorene, phenan-

threne, anthracene, ﬂuoranthene, pyrene, benz[a]anthra-

cene, chrysene, benzo[b]ﬂuoranthene, benzo[k]ﬂuoranthene,

benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenz[a,h]anthra-

cene and benzo[g,h,i]perylene) than the Fe3O4@mSiO2-Ph,

but also had a higher selectivity for PAHs than n-alkanes

due to the π–π interactions, which mediate adsorption. The

MSPE method was applied to soil extracts and signiﬁcantly

improved sample clean-up regarding the direct analysis or

silica clean-up (Table1) [36].

Ionic liquids are also attracting functionalization of mag-

netic materials. Composites with immobilized ionic liquids

have been proposed for MSPE of PAHs. A dicationinc

ionic liquid was prepared reacting 2,5 dichloro-p-xylene

with 1-benzylimidazole. Fe3O4 NPs, already covered with

polyaniline, were further functionalized with the dicationic

ionic liquid-bis(triﬂuoromethylsulfonyl)imide (NTf2) by the

self-assembly coating method. Pre-concentration and separa-

tion of ﬁve PAHs occurred because of the π–π interaction

between the polyaniline shell and the dicationic ionic liquid

with PAHs. The MSPE method was coupled with GC–MS

for detection in environmental samples (water, sludge, soil)

(Table1) [37].

Magnetic Solid‑phase Extraction ofMetals

The MSPE of heavy metals has been recently reviewed

for diﬀerent materials, magnetic NPs covered with silica,

oxides, imprinted or non-imprinted organic polymers,

MOFs, magnetic ionic liquids, composites with carbon

materials and biosorbents [38]. The use of magnetic gra-

phene composites and derived materials for enrichment of

heavy metals was also reviewed in 2018 [4]. Concerning

MSPE of metals using MIPs, applications to Cu(II) have

been recently reported [6]. Metals were also extensively

enriched by MSPE using MOFs, with applications to Cd(II),

Zn(II), Ni(II), Hg(II) and Pb(II) in ﬁsh and shrimps [17].

More recent MSPE applications to metals, which have not

been reported in previous reviews, include the description of

a magnetic graphene composite, where functionalization was

achieved with silica-cyanopropyl, developed for the removal

of Pb(II) ions in water. The material combined diﬀerent fea-

tures, i.e., magnetism, a triple bond for lead complexation

and porosity of SiO2. The binding process was shown to be

pH dependent, and the maximum adsorption capacity for

Pb(II) removal was found to be 111.11mgg−1 at pH 5.0

(Table1) [39]. After incubation, unbound lead was meas-

ured by ﬂame atomic absorption spectroscopy at 261.42nm.

The authors investigated the kinetics and thermodynamics

of Pb(II) binding but did not develop any analytical method

for determination or quantitation.

Biopolymers are attracting attention also in MSPE of

metals. For instance, a diphenyl diselenide composite with

Fe3O4@chitosan was recently used for separation of Pb(II),

Cd(II), Ni(II) and Cu(II) in different samples (sausage,

drinking water, wastewater). Chitosan is an abundantly

available, inexpensive, renewable, non-toxic, biocompat-

ible and biodegradable amino-polysaccharide biopolymer.

The authors described a modiﬁed version of the traditional

MSPE, where mixing is achieved by eﬀervescence. The

composite was packed into a tablet with sodium carbonate

and citric acid so that, once placed in the sample solution,

carbon dioxide gas would be released for 30s, allowing dis-

persion of the material and analyte binding (Table1) [40].

A variation of PDA chemistry has also been recently sug-

gested for isolation of trace metals. Catechol was polymer-

ized on Fe3O4 NPs to prepare a core–shell material under

mild oxidative conditions. The material thus prepared was

then used for MSPE of seven heavy metals (Cd(II), Co(II),

Cr(III), Cu(II), Mn(II), Ni(II) and Pb(II)) in water (well and

mineral) and fruit samples (apples, pomegranate, water-

melon, kiwi). The MSPE method was performed on digested

samples and coupled with ICP-OES [41]. The material was

particularly selective and sensitive because of the formation

of 1:2 metal complexes with the catechol moiety (Table1)

[42].

Nanomaterials are particularly suited for the trace analy-

sis of metals; for instance, the core shell material Fe3O4@

MnO2 was used for ultra-trace analysis of As(III). The

MSPE method was coupled with chemical hydride gen-

eration-atomic ﬂuorescence spectrometry and applied to

1267Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

environmental water samples (river, spring, rain, lake). The

slurry sampling hydride generation method allowed to sig-

niﬁcantly reduce the desorption time from a few minutes for

the traditional elution method to a few seconds, thus greatly

improving the eﬃciency of analysis (Table1) [42].

Biosorbents appear particularly attractive in the context

of MSPE of metals to comply with the need for sustainable

and eco-friendly materials. Recently, an edible but tasteless

common mushroom (Coprinus micaceus) was employed

to prepare a biosorbent for Co(II) and Hg(II). The fungal

biomass was immobilized on iron NPs and applied to food

(potato, cabbage, ketchup, green pepper, meat, tuna, chicken,

milk) and water (tap, mineral, river) samples. The biosorb-

ent was simply obtained by mixing the dried fungal biomass

with magnetic NPs and by wetting/drying cycles to improve

contact. The obtained material was ﬁnally ground and sieved

to the desired particle size. Despite the magnetic proper-

ties of the biosorbent, it was packed in a cartridge for use

(Table1) [43].

Magnetic Solid‑phase Extraction ofToxins

Nanomaterials used for assay of phytotoxins were recently

reviewed and include the description of MSPE using MOFs

for analysis of colchicine in colchicine roots, cyanide in

water (tap, ground and lake), ricin B-chain in orange juice

and caster beans and ricin A-chain in milk and water [44].

Fe3O4@PDA was used for MSPE of aﬂatoxins in liquid

foodstuﬀ samples [5]. MOFs were described for MSPE of

toxins; in particular, they were applied to domoic acid to

assess shellﬁsh poisoning [17].

Magnetic graphene composites and derived materials

have been recently reviewed and include application mainly

to aﬂatoxins in food [4]. Another application, which is not

included in the previously cited review, describes the MSPE

of zearalenone with magnetic nanografene in corn. The

method was coupled with HPLC and ﬂuorescence detec-

tion (Table1) [45]. Among the carbon materials, graphitized

carbon black was also used to prepare magnetic materials by

procedures similar to those applied to graphene. Magnetic

graphitized carbon black was used for the extraction of six

mycoestrogens (β-zearalanol, β-zearalenol, α-zearalanol,

α-zearalenol, zearalanone, zearalenone) in cow milk [46]

and six mycotoxins (aﬂatoxins G2, G1, B2 and B1, ochra-

toxin A, zearalenone) in cereals (Triticum durum ﬂour and

Zea mays meal) (Table1) [47]. Amino-modiﬁed magnetic

MWCNTs were used for MSPE of aﬂatoxin B1 and zearale-

none in wheat ﬂour samples. The material was selective and

recognized analytes with multi-aromatic rings in their struc-

ture due to π–π and hydrogen-bonding interactions (Table1)

[48]. The developed MSPE method not only was competitive

with previously reported methods, but also complied with

the principles of green analytical chemistry, as it scored 89

out of 100 on the Eco-Scale proposed by Gałuszka etal.

[49].

Magnetic MIPs have also been used for MSPE of toxins.

Applications to citrinin in rice samples and to the tumor-pro-

moter microcystins in water have already been reported [6].

Also, six mycotoxins (deoxynivalenol, 3-acetyldeoxyniva-

lenol, 15-acetyldeoxynivalenol, fusarenon-X, T-2, and HT-2

toxin) were investigated in rice using core-shell magnetic

MIP sorbents. The preparation of the material was reﬁned,

and the authors indicated that better size control could be

achieved using Fe3O4 superﬁcially covered with oleic acid.

Imprinting was achieved by precipitation polymerization

of methacrylic acid and divinylbenzene using deoxynivale-

nol as the imprinting molecule for the whole analyte class

because of the structural similarity. An MSPE method was

optimized and coupled with HPLC–MS detection (Table1)

[50]. A hybrid material containing a Co3O4 magnetic core,

coated with carbon and with an outer poly(methacrylate-co-

EGDMA) MIP shell, was recently used for MSPE of aﬂa-

toxins. The dummy template, ethyl 3-coumarincarboxylate,

was used for MIP preparation. The method was coupled with

HPLC–MS analysis and applied to the determination of aﬂa-

toxins in corn samples (Table1) [51].

Magnetic Solid‑phase Extraction ofOther Common

Pollutants, Contaminants andMultiresidue Methods

Magnetic graphene composites and derived materials have

been recently reviewed for dye analysis mainly in food [4].

Magnetic MIPs were reviewed with applications to mala-

chite green in ﬁsh samples, rhodamine B in wine and sudan

dyes (Sudan I, II, III and IV) in food [6]. MOFs were used

for MSPE enrichment of dyes, in particular triphenylmeth-

ane dyes in ﬁsh and sudan dyes in tomato juice [17]. Fe3O4@

PDA was used for the enrichment of synthetic colorants in

liquid foodstuﬀ samples [5]. Alternative magnetic materi-

als were recently proposed for the extraction of common

dyes. 3D magnetic hollow porous CdFe2O4 microspheres,

simply prepared by a one-step hydrothermal synthesis,

were applied to extraction of three azo colorants (Acid Red,

Congo Red, Sunset Yellow) in food. Compared with conven-

tional CdFe2O4 NPs, the new 3D material exhibited superior

extraction capability due to the hollow porous structure and

high speciﬁc surface area. The extraction method was com-

bined with HPLC–UV (Table1) [52]. Finally, a variation of

the usual MSPE was recently described in the literature and

applied to dye analysis. Instead of using magnetic materi-

als dispersed in a sample, a magnetic textile was prepared.

The approach exploited ligands immobilized on the textile

structure to speciﬁcally bind the target analytes and an iron

staple inserted at the top of the textile square to provide the

material with magnetic responsiveness. Textiles have the

advantage of being cheap and easy to modify. For example,

1268 A.L.Capriotti et al.

1 3

an acrylic felt was modiﬁed with copper phthalocyanine dye

and used to extract trace amounts of two dyes (crystal violet

and Safranin O). The dyes were desorbed from the textile

and measured by UV-Vis spectroscopy [53]. The textile is

particularly versatile and was also functionalized with chi-

tosan for the extraction of blue fountain ink dye (acid blue

93) from extremely diluted water extracts [54] and food acid

dye (tetrazine, azorubine, indigo carmine) [55]. In the lat-

ter example, detection and a semiquantitative analysis were

achieved directly without elution by image analysis of a

picture of the textile using a smartphone, a computer and

freeware software (Table1).

An hybrid carbon material made up of graphene

oxide conjugated to magnetite NPs and then coated with

poly(methyl methacrylate) was used for the enrichment of

aromatic amines (aniline, N,N-dimethylaniline, o-toluidine

and 3-chloroaniline), which are priority pollutants with

carcinogenic activity, from environmental water samples

coupling the MSPE with GC. The method was successfully

applied to the determination of aromatic amines in spiked

real water samples (Table1) [56].

Acrylamide is a common contaminant found in food, as

it is formed during cooking of carbohydrate-rich food at

temperatures > 120°C. In a recent report, a magnetic MIP

was proposed for acrylamide pre-concentration in biscuits.

An eco-friendly preparation, by a dummy template strategy,

was used and performed in aqueous media. Fe3O4 NPs were

ﬁrst encapsulated with a polyethylene glycol layer, and then

chitosan was polymerized and imprinted using propanamide

as dummy template. The MSPE method was coupled with

HPLC–UV analysis (Table1) [57].

Plant growth regulators, extensively used in agriculture

to improve production, are potentially toxic for humans

and animals and could contaminate food. In this regard, a

method for the determination of seven plant growth regula-

tors was developed for vegetable samples exploiting MSPE

coupled with HPLC–MS. A hybrid magnetic material was

prepared by functionalization of Fe3O4 with graphene

oxide, β-cyclodextrin and an ionic liquid (Fe3O4@SiO2/

graphene oxide/β-cyclodextrin/ionic liquid). Compared

with Fe3O4 simply functionalized with graphene oxide or

β-cyclodextrin, the ionic liquid (1-vinyl-3-octylimidazolium

1-anthraquinonesulfonic acid) endowed the material with an

improved aﬃnity due to the synergy and multiple interac-

tions established with the analyte (π–π interactions, hydro-

phobic interactions, electrostatic interactions, host-guest

inclusion complexes formation, hydrogen bonds and other

non-covalent bonds) (Table1) [58].

Among the recent reports, magnetic materials were used

as clean-up within a modiﬁed Quick, Easy, Cheap, Eﬀective,

Rugged and Safe (QuEChERS) method for the simultaneous

determination of 48 veterinary drugs (26 sulfonamides, 6

β-lactams, 7 macrolides, 3 nitroimidazoles, 2 lincosamides,

2 chloramphenicols, 2 abamectins), 13 pesticides and 13

mycotoxins in eggs and coupled with HPLC separation and

MS detection (Table1) [59]. The prepared material was

based on magnetic MWCNTs. The magnetic properties were

exploited to improve analysis times and speed up the recov-

ery of the adsorbent compared with the traditional centrifu-

gation process. This method was successfully applied to the

analysis of 48 egg samples, and 16 targets were observed.

More than 50% of the egg samples were contaminated, and

approximately 23% contained more than three kinds of

analytes.

Another recent multiresidue method exploited the

insitu preparation of core-shell magnetic porous aromatic

framework (Fe3O4@SiO2@PAF-6) NPs using cyanuric

chloride as a planar trigonal basis upon which to build a

linear piperazine linker unit. The material was applied to

the pre-concentration of seven organic pollutants (phenol,

2,4,6-trinitrophenol, naphthalene, naphthol, bisphenol A,

2,4-dichlorophenol, 3-nitrochlorobenzene) in water (well,

tap, river water, wastewater) and coupled with HPLC–UV/

ﬂuorescence. The same material was also applied to remove

> 50% of the main toxic compounds in cigarette smoke,

including phenolic compounds and benzo[a]pyrene. The

aﬃnity of the material was investigated by computational

approaches, which indicated the suitability for adsorption

of aromatic compounds, especially phenols, PAHs and

nitroaromatics, due to the π-π stacking and hydrogen-bond

interactions (Table1) [60].

Magnetic Solid‑phase Extraction ofPeptides,

Proteins andOther Biologic Macromolecules

The use of magnetic materials for sample preparation in bio-

logic matrices has been reviewed [61] with several applica-

tions, also for the isolation and enrichment of peptide and

protein biomarkers [62]. Magnetic functional materials

have been extensively exploited for phosphopeptide enrich-

ment, and they can be made up of polymers in immobi-

lized metal aﬃnity chromatography (IMAC) approaches,

or metal oxides, in metal oxide aﬃnity chromatography

(MOAC) approaches [63]. IMAC and MOAC are traditional

approaches; nevertheless, new materials exploiting aﬃnity

chromatography to metal cations or oxides are continuously

developed. For instance, a hydrophilic support for Ti4+ was

developed by polymerization of glycidyl methacrylate by a

“grafting from” approach by the activator regenerated by

the electron transfer-atom transfer radical polymerization

technique and was successfully applied to the enrichment

of phosphopeptides from cell lysate digests [64] and serum

in a shotgun proteomics workﬂow [65].

Magnetic graphene composites and derived materials

have been recently reviewed [4] and include applications to

1269Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

the enrichment of phosphopeptide and endogenous peptides

in diﬀerent biologic samples. Other carbon materials were,

nevertheless, extensively used for biologic macromolecules

enrichment. For instance, graphitized carbon black was mag-

netized with Fe3O4 and covered with TiO2 for the enrich-

ment of phosphopeptides in shotgun proteomic workﬂows

from complex cell extracts [66] and saliva [67].

PDA grown on magnetic particles was extensively used

for the extraction of biomolecules because of its easy prep-

aration, hydrophilicity and biocompatibility. Fe3O4@PDA

was used for the enrichment of genomic deoxyribonucleic

acid. Many variations have been proposed for such base

material because of the derivatization simplicity of PDA.

Metal cations were immobilized on the surface [68], along

with MOFs for enrichment of phosphopeptides. Bovine

serum albumin, bovine hemoglobin and horseradish peroxi-

dase were enriched using Fe3O4@PDA coupled with MIPs.

Hybrid materials made up of PDA with magnetic graphene

were developed and applied to diﬀerent macromolecules,

included phosphopeptides, glycopeptides and N-linked gly-

can, also with further modiﬁcation.

Magnetic MIPs were used to detect proteins, in particular

bovine hemoglobin in bull’s blood, and peptides, such as

insulin in human serum [13]. PDA can also be imprinted

with a template protein to produce an MIP. For instance,

it was recently used as the functional monomer and cross-

linker to form an imprinted layer for puriﬁcation of bro-

melain, a commercially valuable cysteine endopeptidase

enzyme. Pericarpium granati, a common biologic waste

product, was chosen as the starting carbon source for fab-

rication of biomass-derived magnetic porous carbon by

hydrothermal carbonization. A competitive study with other

proteins in a standard protein solution indicated that the

developed material distinguished proteins on the basis of the

synergistic eﬀect of the 3D complementarity and multiple

non-covalent interactions (Table1) [69]. Hybrid materials

combining an imprinted PDA shell and MWCNTs in the

core were used for speciﬁc recognition of lysozymes from

egg white [5].

Hybrid materials have also been developed for large

biomolecule analysis, such as the one that coupled Fe3O4

with MIPs and deep eutectic solvents. A polymerizable

deep eutectic solvent vinyl monomer [(3-acrylamidopro-

pyl)trimethylammouium chloride and urea, 1:2 ratio] was

polymerized using N,N’-methylene-bis-acrylamide as cross-

linker and used to prepare an MIP for bovine hemoglobin.

The prepared material showed a good aﬃnity for the tem-

plate, with an imprinting factor of 4.93. The material was

ﬁnally applied to enrich bovine hemoglobin from calf blood.

Sodium dodecyl sulfate–polyacrylamide gel electrophoresis

conﬁrmed isolation of bovine hemoglobin and absence of

bovine serum albumin, which is the most abundant protein

in blood (Table1) [70]. Older examples of this approach, in

which a deep eutectic solvent is used in combination with

magnetic NPs to produce composite materials, have been

previously discussed for bovine hemoglobin and trypsin

[71].

Another example of hybrid material for the selective

binding of proteins was prepared using ionic liquids: vinyl-

modiﬁed Fe3O4@SiO2 NPs were derivatized with an MIP

for the binding of bovine serum albumin. The MIP was

prepared using three functional monomers: a polymeriz-

able ionic liquid (1-vinyl-3-(2-amino-2-oxoethyl) imidazo-

lium chloride, [VAFMIM]Cl), N-isopropylacrylamide and

α-methacrylic acid. The ﬁnal material resulted with a hollow

cavity after etching of the silica layer and template removal.

The material was characterized and showed good selectivity

for bovine serum albumin in competitive studies with other

proteins [72].

COFs were employed for peptides and N-glycopeptides

in human serum [1]. MOF application to biomolecules was

recently reviewed [7, 73]. Magnetic versions of these mate-

rials typically include a magnetic core made up of Fe3O4

and were applied to enrichment of low abundance peptides,

phosphopeptides, glycopeptides, glycoproteins, glycans and

proteins.

Magnetic Solid‑phase Extraction

ofMetabolites andNatural Compounds

Carbon composite materials were recently described for the

enrichment of the phytohormones in plants. More speciﬁ-

cally, graphene oxide supported on Fe3O4@SiO2 NPs was

used for the enrichment of cytokinins from tobacco leaves.

The method was developed for four cytokinins and coupled

with HPLC–MS detection (Table1) [74]. Magnetic materi-

als based on PDA were used for investigation of berberine

from Cortex Phellodendri [5].

Magnetic MIPs were also used for analysis of bioac-

tive compounds. As recently reviewed [6], magnetic MIPs

were used for the investigation of the anticancer and anti-

inflammatory compound quercetagetin, which is abun-

dant in Calendula oﬃcinalis, for curcumin in food and for

polyphenolic antioxidants in Polygonatum odoratum; sur-

face-imprinted MWCNTs@PDA-MIPs were prepared for

cinnamic acid, ferulic acid and caﬀeic acid from a Radix

scrophulariae sample [5]. In a recent application, magnetic

MIPs were also used for MSPE of the anti-leukemic agent

6-mercaptopurine and its active metabolite thioguanine

in human plasma. A computational approach was used to

select the most suited monomer from ﬁve candidates, in ﬁve

solvents, by investigating the possible template-monomer

complexes. The ﬁnal material was synthesized via precipi-

tation polymerization and non-covalent imprinting from

methacrylic acid and EGDMA in methanol. The developed

1270 A.L.Capriotti et al.

1 3

MSPE method was coupled with HPLC–MS detection

(Table1) [75].

Recently, magnetic NPs coated by an amino-terminated

supramolecular cucurbit [6] uril (CB [6]) pseudorotaxane

motif were fabricated for enrichment of salvianolic acids

from medicinal plants. The material was prepared by cucur-

bit [6] uril promoted azide-alkyne cycloaddition. The CB

[6] unit proved useful for recognition as it provided multiple

chemical interaction sites and unique chemical selectivity

(Table1) [76].

Chelerythrine is a bioactive compound isolated from

Macleaya cordata (Willd) R. Br. (M. cordata) with anti-

inﬂammatory, antidiabetes, antifungus, antibacterial and

pesticidal activities. Magnetic MIPs were used for the

isolation of such compound. A traditional approach was

exploited, preparing Fe3O4@SiO2 as a magnetic support,

chelerythrine as template, methacrylic acid as functional

monomer and EGDMA as cross-linker. Molecular simula-

tion and calculation of the self-assembly between the target

analyte and monomer were used to choose the best synthetic

strategy, which indicated the 1:4 molar ratio to provide the

highest complex stability. The material was ﬁnally applied

to the separation of the target analyte from a M. cordata

extract (Table1) [77].

The gastric cancer biomarkers p-hydroxybenzoic acid

and p-cresol were isolated by MSPE in human urine using

a porous magnetic β-cyclodextrin polymer. The material

was prepared by functionalization of the Fe3O4 core ﬁrst

with meso-2,3-dimercaptosuccinic acid and ﬁnally with

β-cyclodextrin. The MSPE was coupled with HPLC–DAD

detection, and validation suggested the possibility of using

this strategy for early gastric cancer detection (Table1) [78].

Deep eutectic solvents were used to prepare hybrid MIP

materials for MSPE of bioactive compounds from tea. Chi-

tosan-covered Fe3O4 NPs were furthered derivatized with

an MIP prepared using the deep eutectic solvent (choline

chloride/methacrylic acid, 1:2 molar ratio) as monomer

and EGDMA as cross-linker, with (+)-catechin as template

molecule, for enrichment of (+)-catechin, (−)-epicatechin

and (−)-epigallocatechin gallate in black tea. The mate-

rial showed a good recognition and loading capacity, with

potential application in separation of bioactive compounds

from tea (Table1) [79]. Ternary deep eutectic solvent mag-

netic MIPs were developed for the selective separation of

theophylline, theobromine, (+)-catechin hydrate and caﬀeic

acid from green tea. The ternary deep eutectic solvents are

obtained by addition of a third component to a binary deep

eutectic solvent and allow avoiding some common disad-

vantages of ordinary deep eutectic solvents, such as the high

viscosity and high melting points. A Fe3O4@SiO2 magnetic

core was covered with the MIP, obtained by polymerization

of the ternary deep eutectic solvent (choline chloride/oxalic

acid/propylene glycol, 1:1:1 molar ratio) with EGDMA

as cross-linker and a mixture of the four target analytes as

templates. The MSPE method was coupled with HPLC–UV

detection (Table1) [80].

Magnetic Solid‑phase Extraction

inthePerspective ofGreen Analytical

Chemistry

MSPE is a technique that evolved over time to comply with

the principle of green chemistry. Due to the possibility of

recovering the phase by application of a magnet, MSPE is

considered to be more environmentally friendly than tra-

ditional energy-, time- and solvent-consuming procedures;

in fact, MSPEs protocols usually require low amounts of

sorbent material, which in most cases can also be re-used

several times without a signiﬁcant loss in performance, short

extraction times and a limited number of steps, all features

that satisfy the principles of green analytical chemistry [81,

82]. In this sense, green sample preparations for bioana-

lytical samples have recently been discussed also for MSPE

procedures [83]. A special advantage is also provided by

the combination of MSPE with other microextraction tech-

niques, as recently described in [84].

One of the most eﬀective couplings is with DLLE, as

previously described [11, 12, 30, 32], which allows purify-

ing the target analyte and reducing the matrix eﬀect, while

improving method sensitivity by combination of the beneﬁts

from adsorption and solvent extraction [84].

The nature of loading and elution solutions also con-

tributes to the environmental impact of an MSPE method.

The reduction or avoidance of organic solvents represents a

strategy to improve the environmental compatibility of new

MSPE procedures. For instance, a pH-controlled MSPE

method was described for the determination of paraquat

and diquat, two popular quaternary ammonium herbicides

in waters. The target analytes are extremely soluble in water

and insoluble in organic solvents; thus, a diﬀerent binding/

elution approach was pursued based on pH. To capture them,

carboxymethyl-β-cyclodextrin was immobilized on silica-

coated magnetic nanoparticles and was used for supramo-

lecular host-guest interaction with the analytes. Binding and

elution of the target analytes were achieved by simple pH

change without need for any organic solvent [85].

One important aspect to be considered in the develop-

ment of green MSPE procedures is the material prepara-

tion. Apart from a few examples discussed in the previous

sections in which environmentally friendly materials are

prepared [22, 57], some materials better comply than others

with the development of environmentally friendly analyti-

cal procedures. For example, a green and eﬃcient sorbent

that has been adapted for MSPE methods is graphitic carbon

nitride (g-C3N4). The material has an aromatic tri-s-triazine

1271Recent Applications ofMagnetic Solid-phase Extraction forSample Preparation

1 3

structure, which resembles the structure of graphene and

provides a variety of interactions suitable for separation,

such as complexion, hydrogen bond, redox reaction, π–π

conjugation, hydrophobic eﬀect, acid–base reaction and

electrostatic interactions. Many facile methods are avail-

able for the synthesis of graphitic carbon nitride, some of

which starts from nitrogen-rich green precursors, such as

melamine and urea; moreover, the easy exfoliation and good

biocompatibility make it greener than traditional materials

(polymers, carbon nanotubes, etc.). Graphitic carbon nitride,

magnetized by immobilization of magnetite nanoparticles

on the surface, was used for the MSPE of phenolic acids,

phthalate esters, PAHs and brominated ﬂame retardants

from water, as recently reviewed [86]. Halloysite nanotubes

represent another type of environmentally friendly material,

which is also a cheaper and greener alternative to traditional

carbon nanotubes. Halloysite is a natural aluminosilicate

clay having a hollow nanotube structure and can be eas-

ily magnetized by a simple co-precipitation method. The

material was used to extract anionic azo dyes (methyl red

and methyl orange) from water in combination with an ionic

liquid [C16mimBr], with which mixed hemimicelles were

formed. The method was coupled with HPLC–DAD detec-

tion and applied to tap and lake water samples [87].

Materials prepared from low-cost wastes are also eco-sus-

tainable. Most of the papers that fall into this category use

a waste product that is converted into a carbon material to

prepare a magnetic sorbent for MSPE [69]. In this category

falls a recent report on the preparation of magnetic submi-

crocube graphitic structures by pyrolysis of waste napkins

from restaurants. The material was applied to the MSPE

of ﬁve phthalate esters in two beverages and plastic bottles

[88]. Another recent example uses pomelo peels to prepare

a carbon material, later magnetized with Fe3O4 by co-pre-

cipitation. The material was ﬁnally employed for MSPE of

environmental pollutants (eight parabens, including meth-

ylparaben, ethylparaben, propylparaben, isopropylparaben,

butyl-paraben, isobutylparaben, heptyl 4-hydroxybenzoate,

2-ethylhexyl-4-hydroxybenzoate and 7 ﬂuoroquinolones,

including marboﬂoxacin, norﬂoxacin, ciproﬂoxacin, lome-

ﬂoxacin, enroﬂoxacin, saraﬂoxacin and sparﬂoxacin) [89].

Conclusions

This minireview gives an overview of the latest applications

of MSPE in sample preparation. The minireview provides a

bird’s-eye view on the topic, without being comprehensive,

but still referring to latest the research works and review

articles, speciﬁc to a certain material type or type of sample.

The most recent applications were selected, especially if not

covered by previous review articles in this ﬁeld, to provide

the state of the art and new suggestions for material and

method development for MSPE. What emerges from this

scan of the recent literature is that MSPE greatly beneﬁts

from the developments of material chemistry, as most of

the materials were actually developed for diﬀerent purposes

than MSPE. There are speciﬁc needs that still need to be

addressed and are rarely considered, especially the need to

comply with environmentally friendly methodologies, from

greener material preparations to miniaturized scale sample

preparation and reduced employment of organic solvents,

while maintaining the top analytical performance needed

for validation of new analytical methods.

Compliance with Ethical Standards

Conflict of interest The authors declare that they have no conﬂict of

interest.

Human and animal rights statement This article does not contain any

studies with human participants or animals performed by any of the

authors.

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Innovative Solid-Phase Extraction Strategies for Improving the Advanced Chromatographic Determination of Drugs in Challenging Biological Samples

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MOLECULES

In the past few decades, considerable scientific strides have been made in the subject of drug analysis in human biological samples. However, the risk caused by incorrect drug plasma levels in patients still remains an important concern. This review paper attempts to investigate the advances made over the last ten years in common sample preparation techniques (SPT) for biological samples based on solid sorbents, including solid-phase extraction (SPE) and solid-phase micro-extraction (SPME), and in particular in the field of molecularly imprinted polymers (MIPs), including non-stimuli-responsive and stimuli-responsive adsorbents. This class of materials is known as ‘smart adsorbents’, exhibiting tailored responses to various stimuli such as magnetic fields, pH, temperature, and light. Details are provided on how these advanced SPT are changing the landscape of modern drug analysis in their coupling with liquid chromatography-mass spectrometry (LC-MS) analytical techniques, a general term that includes high-performance liquid chromatography (HPLC) and ultra-high performance liquid chromatography (UHPLC), as well as any variation of MS, such as tandem (MS/MS), multiple-stage (MSn), and high-resolution (HRMS) mass spectrometry. Some notes are also provided on coupling with less-performing techniques, such as high-performance liquid chromatography with ultraviolet (HPLC-UV) and diode array detection (HPLC-DAD) detection. Finally, we provide a general review of the difficulties and benefits of the proposed approaches and the future prospects of this research area.

Advancements in magnetic nanoparticle-based biosensors for point-of-care testing

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Apr 2024

The significance of point-of-care testing (POCT) in early clinical diagnosis and personalized patient care is increasingly recognized as a crucial tool in reducing disease outbreaks and improving patient survival rates. Within the realm of POCT, biosensors utilizing magnetic nanoparticles (MNPs) have emerged as a subject of substantial interest. This review aims to provide a comprehensive evaluation of the current landscape of POCT, emphasizing its growing significance within clinical practice. Subsequently, the current status of the combination of MNPs in the Biological detection has been presented. Furthermore, it delves into the specific domain of MNP-based biosensors, assessing their potential impact on POCT. By combining existing research and spotlighting pivotal discoveries, this review enhances our comprehension of the advancements and promising prospects offered by MNP-based biosensors in the context of POCT. It seeks to facilitate informed decision-making among healthcare professionals and researchers while also promoting further exploration in this promising field of study.

Extraction and preconcentration of lead (II) in various water and food samples by orbital shaker-assisted magnetic solid phase extraction method using a new magnetic poly linoleic acid-polystyrene-PDMS block copolymer

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FOOD CHEM

Recent Advancement and Prospects of Novel Nanomaterial-Based Solid-Phase Extraction (SPE) Techniques

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In this review, the principles and characteristics of solid-phase extraction (SPE) are discussed. The categories of nanomaterial-based adsorbents namely metal/metal oxides, magnetic nanoparticles, silica-based nanoparticles, two-dimensional (2D) nanomaterials (NMs), polymeric nanoparticles, nanotubes, semiconductor NMs, and nanoporous materials along with their features are discussed followed by evaluating their synthetic strategies. Finally, the application of nanomaterial-based sorbents for extraction and preconcentration of drugs, pesticides, and heavy metals in biological, food, and environmental samples is assessed. Overall, the future of SPE techniques is expected to include advances in downsizing, automation, selectivity, sustainability, and integration with other analytical techniques, resulting in more efficient and effective sample preparation procedures for a variety of applications.

Magnetic iron-based metal organic framework as an adsorbent for magnetic dispersive solid-phase extraction of pyrene and phenanthrene in water samples

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Application of continuous magnetic solid phase extraction in the extraction of tetracycline antibiotics from honey samples

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Greenness assessment of microextraction techniques in therapeutic drug monitoring

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Mar 2024

Aim: In this study, we evaluated the greenness and whiteness scores for microextraction techniques used in therapeutic drug monitoring. Additionally, the cons and pros of each evaluated method and their impacts on the provided scores are also discussed. Materials & methods: The Analytical Greenness Sample Preparation metric tool and white analytical chemistry principles are used for related published works (2007–2023). Results & conclusion: This study provided valuable insights for developing methods based on microextraction techniques with a balance in greenness and whiteness areas. Some methods based on a specific technique recorded higher scores, making them suitable candidates as green analytical approaches, and some others achieved high scores both in green and white areas with a satisfactory balance between principles.

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Dear students and graduated aesthetic cosmetologists, the teaching material we present uses data from research and websites on current topics for face and body treatment that have been used by people for centuries, all with the aim of improving appearance, improving the health of the skin, hair and nails. Students from the Department of Cosmetology at the MIT University College, Bobana Žežova and Sibil Mustafovska helped me in the preparation of this material. Each research offers new dimensions in our practical work. We are of the opinion that this publication will help you master your skills, to have in practice a high level of professionalism, based on scientific claims. . From the Author

Transient isotachophoresis - capillary zone electrophoresis - mass spectrometry method with off-line microscale solid phase extraction pretreatment for quantitation of intact low molecular mass proteins in various biological fluids

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A simple extraction of blue fountain ink dye (Acid blue 93) from water solutions using Magnetic Textile Solid-Phase Extraction

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Sep 2018

A recently developed preconcentration procedure “magnetic textile solid-phase extraction”, based on the use of a magnetically modified textile impregnated with chitosan, was successfully employed for the preconcentration of blue fountain ink dye Acid blue 93 from extremely diluted solutions. This procedure enabled to detect ink dye released from ink written documents immersed in water. The developed procedure can be easily adapted for the detection of large variety of analytes important for environmental, biochemical and forensic analysis.

Magnetically responsive textile for a new preconcentration procedure: Magnetic textile solid phase extraction

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Oct 2018
J Ind Textil

A new preconcentration procedure named ''Magnetic textile solid phase extraction'' was developed. A piece of nonwoven textile (fabric) was used for the immobilization of copper phthalocyanine dye and employed for the adsorption of crystal violet and safranin O from large volumes of sample. The bound dye was eluted into small volume of methanol. The limit of detection and limit of quantification values for safranin O were 2.66 mg/L and 8.87 mg/L, while for crystal violet these values were 2.17 mg/L and 7.23 mg/L, respectively. Linearity in the range 5-100 mg/L was observed. In order to prepare magnetically responsive adsorbent, an iron-based standard staple was inserted in the textile material using an office stapler. The developed procedure can be easily adapted for the detection of large variety of analytes in biochemistry, biotechnology, environmental technology, and forensic analysis.

Diphenyl diselenide grafted onto a Fe3O4-chitosan composite as a new nanosorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction

Article

Full-text available

Nov 2018
MICROCHIM ACTA

Diphenyl diselenide was immobilized on chitosan loaded with magnetite (Fe3O4) nanoparticles to give an efficient and cost-effective nanosorbent for the preconcentration of Pb(II), Cd(II), Ni(II) and Cu(II) ions by using effervescent salt-assisted dispersive magnetic micro solid-phase extraction (EA-DM-μSPE). The metal ions were desorbed from the sorbent with 3M nitric acid and then quantified via microflame AAS. The main parameters affecting the extraction were optimized using a one-at-a-time method. Under optimum condition, the limits of detection, linear dynamic ranges, and relative standard deviations (for n = 3) are as following: Pb(II): 2.0 ng·mL⁻¹; 6.3–900 ng·mL⁻¹; 1.5%. Cd(II): 0.15 ng·mL⁻¹; 0.7–85 ng·mL⁻¹, 3.2%; Ni(II): 1.6 ng·mL⁻¹,.6.0–600. ng·mL⁻¹, 4.1%; Cu(II): 1.2 ng·mL⁻¹, 3.0–300 ng·mL⁻¹, 2.2%. The nanosorbent can be reused at least 4 times. Graphical abstractFe3O4-chitosan composite was modified with diphenyl diselenide as a sorbent for separation of metal ions by effervescent salt-assisted dispersive magnetic micro solid-phase extraction.

A magnetic knitting aromatic polymer as a new sorbent for use in solid-phase extraction of organics

Article

Full-text available

Nov 2018
MICROCHIM ACTA

Magnetic knitting aromatic polymers (Fe3O4/KAPs) are introduced here as a new kind of sorbents. KAPs are hyper-cross-linked-polymers that were prepared via a Friedl-Crafts reaction from triphenylphosphine and benzene as building blocks. The Fe3O4/KAP composite was obtained by coprecipitation of KAP with magnetite nanoparticles. The resulting Fe3O4/KAP is shown to be a viable magnetic sorbent for various organic materials such as the phenylurea herbicides (PUHs), including metoxuron, monuron, chlortoluron, monolinuron and buturon, and also for various phthalates, polycyclic aromatic hydrocarbons and chlorophenols. The Fe3O4/KAP was characterized by means of Brunauer-Emmett-Teller surface area measurements, Fourier-transform infrared spectroscopy, thermogravimetry, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Following desorption with acetonitrile, the analytes were quantified by using HPLC with UV detection. The effects of adsorbent dosage, extraction time, sample pH, ionic strength, desorption solvent and desorption time were optimized for the PUHs. Under optimal conditions, response is linear from 0.5–1.0 up to 50 ng·mL⁻¹ for the five PUHs. Lower limits of detection range between 0.05 and 0.30 ng·mL⁻¹. Other figures of merit include (a) high enrichment factors (60–297), (b) good recoveries (91.8–106.5%), and (c) relative standard deviations of <8.4%. The method was successfully applied to analysis of the PUHs in real samples (bottled mixed juice, milk and soymilk). The results indicate that such Fe3O4/KAPs have a wide application scope as an adsorbent for use in magnetic solid phase extraction. Graphical abstractA magnetic knitting aromatic polymer based nanocomposite (Fe3O4/KAP) was prepared by a one-pot method and explored as an absorbent for magnetic solid-phase extraction (MSPE) of phenylurea herbicides (PUHs) from bottled mixed juice, milk and soymilk samples before quantitation by HPLC with UV detection.

Applications of Metal-Organic Frameworks in Food Sample Preparation

Article

Full-text available

Nov 2018
MOLECULES

Food samples such as milk, beverages, meat and chicken products, fish, etc. are complex and demanding matrices. Various novel materials such as molecular imprinted polymers (MIPs), carbon-based nanomaterials carbon nanotubes, graphene oxide and metal-organic frameworks (MOFs) have been recently introduced in sample preparation to improve clean up as well as to achieve better recoveries, all complying with green analytical chemistry demands. Metal-organic frameworks are hybrid organic inorganic materials, which have been used for gas storage, separation, catalysis and drug delivery. The last few years MOFs have been used for sample preparation of pharmaceutical, environmental samples and food matrices. Due to their high surface area MOFs can be used as adsorbents for the development of sample preparation techniques of food matrices prior to their analysis with chromatographic and spectrometric techniques with great performance characteristics.

Solid-phase extraction of aflatoxins using a nanosorbent consisting of a magnetized nanoporous carbon core coated with a molecularly imprinted polymer

Article

Full-text available

Oct 2018
MICROCHIM ACTA

A core consisting of nanoporous carbon (MNPC) and magnetized with Co3O4 was coated with a molecularly imprinted polymer (MIP) by atom transfer radical precipitation polymerization. Ethyl 3-coumarincarboxylate was used as a pseudo-template to give a MIP that has a fairly specific recognition capability for aflatoxins. Batch rebinding studies were carried out to determine the specific adsorption equilibrium and specific recognition. Extraction is achieved in a single step by mixing and vortexing the sample extract with the Co-MNPC@MIP. The loaded nanosorbent was then magnetically separated and eluted with acetonitrile/water (6/4, v/v). The aflatoxins were then quantified by HPLC. Under optimal conditions, the detection limits for aflatoxins typically are 0.05–0.07 ng mL⁻¹, recoveries from spiked corn are found to be 75.1 to 99.4%, and relative standard deviations range from 1.7 to 5.1 (n = 6). Graphical abstractPoly(methacrylic acid) was imprinted with the pseudo-template ethyl 3-coumarincarboxylate by atom transfer radical precipitation polymerization on the surface of cobalt-derived magnetic nanoporous carbon (Co-MNPC). This nanosorbent was used for the magnetic solid phase extraction of aflatoxins, followed by HPLC analysis.

Semiquantitative determination of food acid dyes by magnetic textile solid phase extraction followed by image analysis

Article

Aug 2019
FOOD CHEM

Magnetic textile solid phase extraction, based on the use of magnetically modified non-woven textile impregnated with chitosan, was successfully employed for the preconcentration of acid food dyes from water solutions. The photos of textile squares with the adsorbed dye were taken with a mobile phone. The image analysis of the photos was performed using appropriate freeware. The values of saturation, obtained through the HSB color space, were proportional to the dye concentration in the analyzed samples. Described inexpensive, simple and elution free assay enables analysis of dyes concentration in various solutions. This novel method has a potential to be a useful alternative to existing semiquantitative determination procedures, especially for dyes analysis.

Amino-terminated supramolecular cucurbit [6] uril pseudorotaxane complexes immobilized on magnetite@silica nanoparticles: A highly efficient sorbent for salvianolic acids

Article

Nov 2018
TALANTA

In this study, a novel amino-terminated supramolecular cucurbit [6] uril (CB [6]) pseudorotaxane motif coated magnetic nanoparticles (MNPs) was successfully fabricated through cucurbit [6] uril promoted azide-alkyne cycloaddition. The physicochemical properties of the obtained functional MNPs were investigated by scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffractometer, vibrating sample magnetometer, thermal gravimetric-derivative thermogravimetric analysis, and Zeta potential analyzer. Due to the abundant carboxyl groups in the structure of CB [6] and amino residue on the surface of the pseudorotaxane motif MNPs, the prepared materials were employed to extract salvianolic acids (SAs) for the first time. A series of significant parameters in the extraction and elution process, including sample pH, acetonitrile percentage, ionic strength and extraction temperature, as well as eluent type and desorption time, were examined systematically. Based on the results, the electrostatic interaction, van der Waals interaction, hydrophilic interaction and hydrogen bonding formation between the analytes and sorbent were speculated. The equilibrium state of static adsorption study indicated the outstanding adsorption capacity of pseudorotaxane motif MNPs toward six SAs to be 15-80 mg/g, providing much better adsorption affinity for SAs compared with MNPs only modified with amino, and their adsorption behaviors were all fitted with Freundlich adsorption isotherm model. In addition, the developed pseudorotaxane motif MNPs offered good recyclability and stability. Taking advantage of these merits, four SAs from Salvia miltiorrhiza Bunge were successfully extracted using the prepared pseudorotaxane motif MNPs with relative recovery in the range from 95.1% to 106.5% and RSDs below 9.7%. These results demonstrated that the synthesized pseudorotaxane motif MNPs showed potential as a candidate in the extraction of SAs.

Dummy molecularly imprinted polymers based on a green synthesis strategy for magnetic solid-phase extraction of acrylamide in food samples

Article

Nov 2018
TALANTA

In this work, novel dummy molecularly imprinted polymers (DMIP) with propanamide as a dummy template molecule were prepared based on a green synthesis strategy of less consumption of hazardous/organic reagents and at mild conditions for magnetic solid-phase extraction (MSPE) of acrylamide in biscuit samples, followed by high performance liquid chromatography (HPLC) determination. The resultant DMIP was well characterized by FT-IR, SEM, TEM and VSM, exhibiting uniform nanoscale coreshell structure and good magnetic property in favor of simple rapid separation. Several main variables influencing MSPE efficiency were investigated, including DMIP dosage, sample solution pH, extraction time and desorption solvent; central composite design (CCD) and response surface methodology (RSM) were employed to assist in the MSPE condition optimization with rapidity and reliability. Under optimized conditions, excellent linearity for acrylamide was obtained in the range of 5.0–5000.0 µg kg⁻¹, and low detection and quantification limits were 1.3 µg kg⁻¹ and 4.4 µg kg⁻¹, respectively. The method recoveries at five spiked concentrations were found within 86.0–98.3% with relative standard deviations (RSDs) of 1.2–4.1%. Furthermore, endogenous acrylamide was detected in five different biscuit samples and the RSDs values were lower than 3.3%. The present study suggested promising perspectives of water-compatible eco-friendly DMIP based MSPE-HPLC method for highly effective sample pretreatment and targeted analytes determination in complicated matrices.

Green construction of Fe3O4@GC submicrocubes for highly sensitive magnetic dispersive solid-phase extraction of five phthalate esters in beverages and plastic bottles

Article

Nov 2018
FOOD CHEM

A well-designed core-shelled Fe3O4@graphitic carbon (Fe3O4@GC) submicrocube was in situ constructed in a simple, relatively green and eco-friendly ways basing on one-step pyrolysis of low-cost waste napkins-coated Fe2O3 submicrocubes. The Fe3O4@GC submicrocubes showed unique architectures where in situ generated thin graphitic carbon layer wrapped on the surface of Fe3O4, resulting in excellent affinity to five phthalate esters (PAEs), good reusability and rapid magnetic separation, therefore were employed as magnetic dispersive solid-phase extraction material combined with HPLC to simultaneously detect five trace PAEs in beverages and plastic bottles. Under optimized conditions, recoveries (80.0%–112.8%), precision (RSDs ≤ 8.8%), and limits of detection (LODs) for beverages (0.09–0.28 μg L⁻¹) and plastic bottles (0.01–0.03 μg g⁻¹) were obtained. This work not only establishes an effective method for simultaneous determination of five PAEs, but also opens up a new strategy to design/construct magnetic graphitic carbon-encapsulated core-shell materials using low-cost/recyclable napkins as carbon source.

Recent Applications of Magnetic Solid-phase Extraction for Sample Preparation

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