Cloud Point Extraction: A Sustainable Method of Elemental Preconcentration and Speciation,

Abstract

Trace elements are gaining increasing attention of scientists working in various analytical fields. Presence or absence of a trace element in a system seriously modifies its intrinsic behavior. Cloud point extraction (CPE) is an upcoming technology to preconcentrate and separate many of the trace elements from different chemical and biological systems. The system is sustainable as it involves benign extractants like surfactants and that too at low concentrations at slightly elevated temperatures to form clouds that separate out from the bulk solution. In addition, the extraction behavior of many elements depends on its chemical species. Keeping in view the need to summarize the research encompassing this technique, many review articles were published which cover a selection of the literature published on this topic over several time spans. A myriad of various technological developments has been reported by several workers. These developments have prompted us to revisit the CP technology with a better understanding of its detection, mechanism and extension to species dependent extraction behavior with regard to the state of art determination of trace metals in our day to day applications. The present article summarizes mainly the results of trace metal preconcentration using CP methodology from different practical samples with an insight to the probable mechanism and speciation involved from 2006 onwards.

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Author's personal copy
Review
Cloud
point
extraction:
A
sustainable
method
of
elemental
preconcentration
and
speciation
Pallabi
Samaddar,
Kamalika
Sen *
Department
of
Chemistry,
University
of
Calcutta,
92
APC
Road,
Kolkata
700009,
India
Contents
1.
Introduction
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1210
2.
Procedures
to
detect
cloud
point
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1210
2.1.
Particle
counting
method
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1210
2.2.
Refractometry
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1210
2.3.
Turbidimetry
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1210
2.4.
Thermo
optical
method
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1210
2.5.
Viscometry
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1211
3.
Reagents
and
methodology
for
cloud
point
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1211
4.
Mechanistic
overview
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1211
5.
Application
to
natural
systems
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1212
6.
Speciation
using
cloud
point
extraction
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1212
6.1.
Iron
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1212
6.2.
Mercury.
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1215
6.3.
Chromium
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1215
6.4.
Arsenic.
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1216
6.5.
Antimony
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1216
6.6.
Selenium
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1217
6.7.
Manganese
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1217
6.8.
Tin
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1217
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
A
R
T
I
C
L
E
I
N
F
O
Article
history:
Received
1
May
2013
Accepted
19
October
2013
Available
online
27
October
2013
Keywords:
Cloud
point
extraction
Trace
element
Speciation
ICP-OES
AAS
A
B
S
T
R
A
C
T
Trace
elements
are
gaining
increasing
attention
of
scientists
working
in
various
analytical
fields.
Presence
or
absence
of
a
trace
element
in
a
system
seriously
modifies
its
intrinsic
behavior.
Cloud
point
extraction
(CPE)
is
an
upcoming
technology
to
preconcentrate
and
separate
many
of
the
trace
elements
from
different
chemical
and
biological
systems.
The
system
is
sustainable
as
it
involves
benign
extractants
like
surfactants
and
that
too
at
low
concentrations
at
slightly
elevated
temperatures
to
form
clouds
that
separate
out
from
the
bulk
solution.
In
addition,
the
extraction
behavior
of
many
elements
depends
on
its
chemical
species.
Keeping
in
view
the
need
to
summarize
the
research
encompassing
this
technique,
many
review
articles
were
published
which
cover
a
selection
of
the
literature
published
on
this
topic
over
several
time
spans.
A
myriad
of
various
technological
developments
has
been
reported
by
several
workers.
These
developments
have
prompted
us
to
revisit
the
CP
technology
with
a
better
understanding
of
its
detection,
mechanism
and
extension
to
species
dependent
extraction
behavior
with
regard
to
the
state
of
art
determination
of
trace
metals
in
our
day
to
day
applications.
The
present
article
summarizes
mainly
the
results
of
trace
metal
preconcentration
using
CP
methodology
from
different
practical
samples
with
an
insight
to
the
probable
mechanism
and
speciation
involved
from
2006
onwards.
ß
2013
The
Korean
Society
of
Industrial
and
Engineering
Chemistry.
Published
by
Elsevier
B.V.
All
rights
reserved.
*Corresponding
author.
Tel.:
+91
9163295148.
E-mail
address:
kamalchem.roy@gmail.com
(K.
Sen).
Contents
lists
available
at
ScienceDirect
Journal
of
Industrial
and
Engineering
Chemistry
jou
r
n
al
h
o
mep
ag
e:
w
ww
.elsevier
.co
m
/loc
ate/jiec
1226-086X/$
–
see
front
matter
ß
2013
The
Korean
Society
of
Industrial
and
Engineering
Chemistry.
Published
by
Elsevier
B.V.
All
rights
reserved.
http://dx.doi.org/10.1016/j.jiec.2013.10.033

Author's personal copy
6.9.
Thallium
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1217
7.
Future
perspectives
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1217
8.
Concluding
remarks
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1217
Acknowledgements
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1218
References
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1218
1.
Introduction
The
cloud
point
(CP)
of
a
solution
is
the
temperature
at
which
the
solution
forms
two
phases.
Cloud
point
preconcentration
(CPP),
based
on
the
clouding
phenomena
of
surfactants
has
drawn
large
attention
in
separation
science.
CPP
offers
many
advantages
over
traditional
liquid–liquid
extraction
[1].
The
two
basic
components
as
a
prerequisite
for
CPP
are
a
salt
solution
and
a
surfactant
solution
which
separates
into
immiscible
surfactant-rich
and
surfactant-poor
phases
[2].
In
the
presence
of
salt,
long-tailed
surfactants
self
assemble
in
aqueous
solution
at
a
particular
temperature
into
long,
flexible
wormlike
micelles,
thus
rendering
the
solution
viscoelastic
[3,4].
An
analyte
interacting
with
micellar
systems
can
therefore
be
concentrated
into
the
surfactant-rich
phase
in
a
small
volume.
Different
elements
at
low
concentrations
influence
various
chemical
and
biological
systems
and
play
vital
roles
in
the
determination
of
their
structure
and
functions
[5–11].
Solvent
extraction
is
a
widely
used
separation
tool
for
rare
earth
metals
[12].
However,
this
method
has
some
problems,
such
as
use
of
toxic
and
flammable
organic
solvents,
poor
extraction-speed,
and
low
concentration
efficiency
for
solute.
Furthermore,
due
to
the
dilution
in
the
organic
phases,
the
mass
action
of
the
extractant
is
decreased
compared
to
that
potentially
present
in
the
pure
compound.
On
the
other
hand,
the
heterogeneous
extraction
at
cloud
point
based
on
surfactants,
are
simple,
rapid
and
powerful
which
extract
the
solutes
existing
in
the
homogeneous
or
pseudo-
homogeneous
aqueous
solution
into
the
water-immiscible
phase
after
the
phase
separation.
Indeed,
the
extractant
is
first
dispersed
in
the
aqueous
phase
by
sonication
and
left
to
settle
at
a
particular
temperature
after
reaction
with
the
metal
cation
to
be
extracted.
These
methods
are
more
inexpensive,
of
lower
toxicity,
and
cause
negligible
environmental
pollution
than
the
conventional
liquid–
liquid
extraction.
Such
methodology
also
provides
high
precon-
centration
factors
[13,14].
The
system
is
highly
sustainable
as
it
involves
the
use
of
benign
extractants
like
surfactants
and
that
too
at
low
concentrations
at
slightly
elevated
temperatures
to
form
clouds
that
separate
out
from
the
bulk
solution.
2.
Procedures
to
detect
cloud
point
There
are
several
procedures
to
detect
the
cloud
point,
some
of
which
are
enlisted
below

Light
scattering
or
particle
counting
method

Refractometry

Turbidimetry

Thermo
optical
method

Viscometry
2.1.
Particle
counting
method
The
particle
counting
method
for
cloud
point
measurement
was
introduced
by
Eliassi
et
al.
[15].
The
basis
of
this
method
is
the
determination
of
the
number
of
particles
in
a
mixture.
When
a
new
phase
appears
in
a
solution,
a
large
number
of
small
particles
are
produced
and
the
solution
becomes
hazy.
The
particles
scatter
the
light
beam
passing
through
it.
By
measuring
the
number
of
particles
in
a
solution
at
various
temperatures,
it
is
expected
that
at
the
temperature
where
a
new
phase
appears,
a
sudden
change
in
number
of
particles
would
be
observed
and
this
temperature
indicates
the
cloud
point
for
the
solution.
Imani
et
al.,
prepared
several
solutions
of
PEG
with
sulfate
salts
with
varying
mass
ratios
of
PEG
to
salt
from
0.8
to
1
and
1–2
[16].
They
used
a
Spectrex
laser
particle
counter
with
a
laser
diode
at
a
wavelength
of
670.8
nm.
The
solution
was
pumped
to
a
flow
cell
and
the
temperature
was
measured
at
the
entrance
of
the
cell
by
a
thermocouple.
At
each
temperature,
the
number
of
particles
was
measured
per
cubic
centimeter
and
at
the
cloud
point,
a
sharp
change
in
the
number
of
particles
was
observed.
2.2.
Refractometry
In
designing
PEG-salt
cloud
points,
different
salt
solutions
e.g.,
K
3
PO
4
,
K
2
HPO
4
,
Na
2
HPO
4
,
and
Na
2
CO
3
along
with
PEG
solution
(MW
=
10,000)
were
mixed.
A
refractometer
equipped
with
a
digital
thermometer
was
used
through
which
water
was
circulated
using
thermostatically
controlled
bath.
The
mixtures
of
solutions
were
directly
injected
into
the
prism
assembly
of
the
instrument
using
a
Hamilton
syringe
stored
at
the
working
temperature
to
avoid
evaporation.
The
refractive
index
measurements
were
done
after
the
liquid
mixtures
attained
the
constant
temperature
of
the
refractometer.
This
procedure
was
repeated
at
least
three
times
[17].
2.3.
Turbidimetry
The
effect
of
salt
concentration
on
CP
temperatures
can
be
studied
by
the
turbidimetry
method
using
a
reaction
calorimeter.
The
calorimeter
is
attached
with
a
glass
head
with
turbidity
sensor,
temperature
sensor
and
a
stirrer
along
with
a
temperature
control
and
programming
device
to
measure
the
CP
temperature
with
the
help
of
the
turbidity
sensor.
The
turbidity
is
measured
in
%
units
(Milli-Q
quality
distilled
water
is
taking
as
reference).
The
second
method
is
to
study
the
transmittance
of
the
solution
was
with
increasing
temperature.
A
slow
heating
rate
of
0.2
8C/min
is
maintained
in
all
the
measurements
to
minimize
the
thermal
lag
between
the
sample
and
the
solution.
The
cloud
point
of
each
sample
is
determined
as
the
average
of
at
least
two
independent
scans.
[18].
2.4.
Thermo
optical
method
Thermo
optical
analysis
(TOA)
provides
a
simple
and
rapid,
method
to
determine
cloud
point
curves
of
binary
polymer/solvent
systems.
The
sample
is
taken
in
a
pyrex
tube
which
is
connected
to
a
vacuum
pump
and
evacuated.
The
tube
is
then
collapsed
and
sealed
by
a
vacuum
when
one
end
is
heated
by
a
flame
while
the
content
of
the
tube
is
maintained
at
sub-ambient
temperature
by
liquid
nitrogen.
The
cloud
point
curves
are
determined
at
the
saturation
vapor
pressure
of
the
solvent.
A
polarizing
microscope
is
fitted
to
it
through
a
photodiode
and
a
microprocessor.
The
heating–cooling
stage
is
designed
for
observation
of
the
thermal
behavior
of
a
sample
under
the
microscope.
The
temperature
program
for
the
given
run
is
entered
into
the
microprocessor.
This
program
consists
of
a
starting
temperature,
a
heating
and
cooling
P.
Samaddar,
K.
Sen
/
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
1210

Author's personal copy
rate,
and
an
end
temperature.
Results
shown
on
the
microproces-
sor
display
are
connected
to
the
PC
for
data
storage
[19].
2.5.
Viscometry
The
cloud
point
separation
of
a
salt
–
poly(ethylene
glycol)
–
water
system
can
also
be
studied
using
viscometry.
The
viscometry
measurements
are
done
using
a
viscometer
equipped
with
a
water
bath
and
a
thermostat
to
control
the
temperature
with
accuracy
of
0.1
8C.
A
chronometer
measured
the
time
of
flow
of
solutions
through
the
U-tube
of
the
viscometer.
On
variation
of
temperature
and
by
visual
inspection
of
solutions
the
cloud
points
were
observed.
The
viscometric
measurement
results
were
plotted
versus
temper-
ature.
The
plots
exhibited
shallow
minima
in
the
viscosity
at
the
cloud
point
temperature.
The
cloud
points
were
determined
at
the
minimum
of
the
curves
obtained
on
plotting
the
measured
viscosities
versus
variation
of
temperature.
The
recorded
tempera-
ture
was
the
cloud
point
of
the
mixture.
The
viscosity
after
passing
through
a
minimum
begins
to
increase
and
then
decrease
again,
but
more
intensively.
This
phenomenon
was
explained
by
the
fact
that
at
higher
temperature
the
molecular
motions
overcome
the
molecular
interactions
and
then,
as
expected,
the
viscosity
decreases.
However,
at
the
cloud
point
the
number
of
particles
of
the
new
phase
suddenly
increases
and
this
causes
an
increase
in
the
viscosity,
which
is
dominant
over
the
viscosity
decrease
because
of
the
temperature
increase
[20].
The
particle
counting
method,
thermo-optical
method
and
viscometry
were
not
developed
further
after
2002,
1991
and
2003
respectively.
3.
Reagents
and
methodology
for
cloud
point
The
general
method
of
cloud
point
extraction
is
presented
schematically
in
Fig.
1
and
pictorially
in
Fig.
2.
The
details
of
metal
(M),
surfactant
(S),
chelating
agent
(C),
temperature
(T),
heating
time
(t),
centrifugation
time
(Y)
and
suitable
reference
(R)
for
various
CPE
have
been
tabulated
in
Table
1.
4.
Mechanistic
overview
Surfactants
are
amphiphilic
compounds
and
have
high
solubi-
lizing
effect
towards
different
substrates.
This
property
has
been
extensively
utilized
in
the
preconcentration
of
metal
ions,
for
studying
the
mobility
of
drugs
in
aqueous
and
lipid
media,
probing
of
biological
systems,
synthesis
of
nano-materials
etc.
These
compounds
aggregate
to
form
various
assemblies
like
monolayers,
micelles,
reverse
micelles
or
vesicles
in
aqueous
as
well
as
organic
media.
Non-ionic
surfactants
undergo
cloud
formation
on
heating,
followed
by
the
formation
of
two
coexisting
isotropic
phases
[46–
49].
Clouding
formation
has
also
been
observed
for
concentrated
aqueous
salt
solutions
of
certain
zwitterionic
and
ionic
surfactants
[50–54].
Clouding
behavior,
also
known
as
coacervate
phase
behavior
or
lower
consolute
behavior,
is
a
typical
physical
change
Metal
(M)
Surf
actant
(S
)
Complexi
ng age
nt (C)
Heat at TºC
For ti
me t
Centrifug
ed for
time
Y
Cooled in
ice
-bath
Dissolved in reag
ent
R
+
+
Fig.
1.
Schematic
diagram
of
general
steps
in
cloud
point
extraction.
Table
1
Conditions
for
cloud
point
extraction
of
different
metal
ions.
M
S
C
T
t
(min)
Y
(min)
R
Reference
Cu
Triton
X-100
Amino
acid
68
8C
10
5
Absolute
methanol
[21]
Co
Triton
X-114
PAN
50
8C
10
10
CCl
4
[22]
Cd
Triton
X-114
APDC
45
8C
20
10
Ethanol
[23]
Cd
Triton
X-114
Dithizone
55
8C
20
10
THF
[24]
Pb
Triton
X-114
Dithizone,
octanol
RT
1
–
HNO
3
in
methanol
(1
mol
L
1
)
[25]
Cd
Triton
X-114
Methyl
green
50
8C
15
10
HNO
3
in
methanol
(1
mol
L
1
)
[26]
Hg
Triton
X-114
PAN,
TAR
50
8C
10
5
Ethanol
[27]
Al
Triton
X-114
Xylidal
blue
50
8C
10
–
HNO
3
in
methanol
[28]
Hg
Triton
X-114
Ammonium
O,O-diethyldithiophosphate
(DDTP)
60
8C
15
5
HCl
in
methanol
[29]
As(III)
Triton
X-114,
SDS
Pyronine
B
45
8C
20
5
1
M
HCl
+
Antifoam
A
[30]
Co
Triton
X-114
4-Benzylpiperidinedithiocarbamate
(K-4-BPDC)
60
8C
10
5
HNO
3
in
ethanol
[31]
Cu
Triton
X-114
N,N
0
-bis(2-hydroxy
acetophenone)-
1,2-propanedimine(L)
35
8C
15
10
HNO
3
in
methanol
[32]
Zn
Triton
X-114
2-methyl-8-hydroxyquinoline(quinaldine),
PAN
70
8C
20
10
HNO
3
in
ethanol
[33]
Al,
Zn
Triton
X-114
8-HQ
45
8C
10
7
Ethanol
[34]
Cd
Triton
X-114
Iodide,
methyl
green
(MG)
50
8C
15
10
HNO
3
in
methanol
[26]
Pb,
Co,
Cu
Triton
X-114
1-Phenylthiosemicarbazide
(1-PTSC)
50
8C
20
10
HNO
3
in
methanol
[35]
Fe,
Cu
Triton
X-114
Erichrome
cyanine
70
8C
15
–
0.02
M
H
2
SO
4
in
ethanol
[36]
Fe
Triton
X-114
2-(5-bromo-2-pyridylazo)-5-
diethylaminophenol
(5Br-PADAP)
50
8C
5
5
Ethanol
[37]
Pb
Triton
X-114
Brilliant
cresyl
blue
(BCB)
40
8C
30
10
HNO
3
in
methanol
(1
mol
L
1
)
[38]
Sn
Triton
X-100
CTAB,
a
-polyoxometalate
55
8C
15
15
DMF
[39]
Mn
Triton
X-100
1-phenyl-3-methyl-4-benzoyl-5-
pyrazolone
(PMBP)
80
8C
25
5
0.1
M
HNO
3
[40]
As
Triton
X-114
Pyronine
B,
SDS
45
8C
20
5
1.0
mol
L
1
HNO
3
in
methanol
[30]
Be
Triton
X-114
Cetyl-pyridinium
chloride
(CPC)
50
8C
10
10
60:40
methanol–water
mixture
containing
0.03
mL
HNO
3
[41]
La,
Eu,
Lu
Triton
X-100
Di(2-ethylhexyl)phosphoric
acid
(HDEHP)
80
8C
60
Water
containing
Arsenazo-III
band
[42]
Zr,
Hf
Triton
X-114
Quinalizarine
55
8C
7
7.5
0.1
mol
L
1
HNO
3
[43]
La,
Gd,
Yb
Triton
X-100
Calixarenes
73–75
8C
15
–
pH
6
acetate
buffer
[44]
U(VI),
Th(IV),
Zr(IV),
Hf(IV)
Triton
X-114
Dibenzoylmethane
(DBM)
50
8C
15
5
20:80
Methanol:1
M
HNO
3
[45]
P.
Samaddar,
K.
Sen
/
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
1211

Author's personal copy
in
the
homogeneous
solutions
of
amphiphilic
substances,
due
to
which
the
solution
separates
into
a
surfactant-rich
and
a
surfactant-lean
phase
at
a
particular
temperature.
The
tempera-
ture,
at
which
this
phase
separation
occurs,
is
known
as
the
cloud
point
(CP)
or
lower
consolute
temperature
(LCT),
an
important
character
of
non-ionic
surfactants.
Clouding
is
ascribed
to
the
efficient
dehydration
of
hydrophilic
portion
of
micelles
at
higher
temperature
condition.
The
micelles
of
the
surfactant
attract
each
other
and
form
clusters
[55]
with
the
approach
of
the
cloud
point
temperature.
Recent
experimental
and
theoretical
investigations
reveal
that
the
formation
of
the
connected
micellar
network
[56–
58]
or
the
H
bonds
between
water
and
the
surfactant
molecules
are
responsible
for
the
lower
consolute
behavior.
The
value
of
CP
depends
on
the
structure
and
concentration
of
the
surfactant
and
the
presence
of
additives
[59,60].
The
clouding
may
also
occur
with
the
change
in
pressure
[61,62]
or
due
to
the
presence
of
certain
additives.
The
mechanism
by
which
this
separation
occurs
is
attributed
to
the
rapid
increase
in
the
aggregation
number
of
the
surfactant’s
micelles,
as
a
result
of
the
increase
in
temperature,
or
any
other
critical
phenomena.
Ethylene
oxide
segments
in
the
micelle
repel
each
other
at
low
temperatures,
when
they
are
hydrated,
and
attract
each
other
as
the
temperature
increases
due
to
dehydration.
This
effect
causes
a
decrease
in
the
effective
area
occupied
by
the
polar
group
on
the
micelle
surface,
increasing
the
size
of
the
micelle
that
can
be
considered
to
become
infinite
at
the
cloud
point,
resulting
in
the
phase
separation.
In
many
cases,
the
addition
of
an
organic
solvent
or
a
salt
prior
to
the
extraction
step
is
necessary
to
reach
efficient
extraction.
The
presence
of
ethanol
produces
an
adequate
increase
on
the
cloud
point
temperature
of
the
system,
higher
preconcentration
factors
and
a
better
kinetics
of
phase
separation.
On
the
other
hand,
the
presence
of
inorganic
electrolytes
decreases
the
cloud
point
temperature
due
to
dehydration
of
the
poly(oxyethylene)
chains.
Additionally,
inor-
ganic
salts
enhance
the
hydrophobic
interactions
among
the
surfactant
aggregates
and
the
analytes,
thus
favoring
their
extraction
from
the
aqueous
to
the
micellar
phase
[1].
In
order
to
decrease
the
viscosity
of
the
surfactant-rich
phase
and
facilitate
its
instrumental
analysis,
it
is
necessary
to
find
an
optimal
diluting
agent
depending
on
the
surfactant
system
employed,
the
instrumental
detection
system
and
the
target
analytes
[63].
When
working
with
AAS,
organic
solvents
such
as
methanol
or
ethanol
containing
strong
acids
are
frequently
used
for
dilution,
offering
appropriate
solution
properties
for
aspiration
and
nebulization.
In
the
case
of
ICP-OES,
the
enriched
surfactant
phase
is
diluted
with
concentrated
acids.
For
absorptiometric
measurements,
the
CPE-extracted
phase
can
be
measured
without
further
treatment,
while
for
flourometric
determination
with
formic
acid,
100%
organic
solvents,
such
as
acetonitrile,
are
employed
when
injecting
the
phase
into
a
CE
instrument.
5.
Application
to
natural
systems
The
cloud
point
technique
has
used
by
several
researchers
to
preconcentrate
and
analyze
different
metal
ions
in
a
large
variety
of
samples.
Tables
2–5
represent
a
glimpse
of
the
variety
of
samples
analyzed
for
their
transition
metal,
lanthanide,
represen-
tative
and
precious
metal
content
preconcentrated
by
cloud
point
technique.
The
extent
of
different
metals
studied
using
cloud
point
extractions
has
been
presented
in
Fig.
3.
6.
Speciation
using
cloud
point
extraction
6.1.
Iron
A
simultaneous
determination
method
for
traces
of
Fe(III)
and
Fe(II)
in
water
was
developed
by
on-line
coupling
of
spectropho-
tometry
with
flame
atomic
absorption
spectrometry
(FAAS).
The
method
involves
cloud
point
extraction
(CPE)
of
both
species
with
ammonium
pyrrolidinecarbodithioate
(APDC)
under
standard
conditions,
which
facilitates
the
in
situ
complexation
and
extraction
of
both
species.
The
method
is
based
on
a
mathematical
modification
of
the
revised
ferrozine
method
which
overcomes
the
Fig.
2.
Pictorial
presentation
of
cloud
point
extraction.
P.
Samaddar,
K.
Sen
/
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
1212

Author's personal copy
Table
2
Cloud
point
preconcentration
of
transition
elements.
Element
Reagent
Sample
type
Method
of
detection
Cu
I)
O,O-diethyldithiophosphate,
Triton
X-100
[64]
II)
N,N
0
-bis(2-hydroxyacetophenone)-
1,2-propanediimine(L)
[65]
III)
Amino
acid
(Chelating
agent),
Triton
X-100
[66]
IV)
Triton
X-100,
Octanol
(cloud
point
revulsant
and
synergic
reagent),
[67]
V)
Monocarboxylic
acids
and
their
mixtures
with
amines
[68]
VI)
N,N
0
-
bis(salicylideneaminoethyl)amine
(H
2
L),
Triton
X-100
[69]
Drinking
water,
blood
serum,
human
hair
Water
Food
and
water
samples
(Certified)
defatted
milk
powder
and
tea
Water
samples
Synthetic
samples
FAAS
FAAS
Spectrophotometry
Spectrophotometry
Atomic
absorption
spectrometry
(AAS)
Spectrophotometry
Zn
2-methyl-8-
hydroxyquinoline(quinaldine),
1-(2-
pyridylazo)-2-naphthol
(PAN),
Triton
X-114
[70]
Medicinal
plants,
blood
samples
of
liver
cancer
patients
FAAS
Co
Polyethyleneglycolmono
polyethyleneglycolmono
p-
nonylphenylethe
[71]
Triton
X-100
and
sodium
dodecyl
sulfate
(SDS),
pyridylazo
compounds
[72]
1-(2-Pyridylazo)-2-naphthol
(PAN),
octylphenoxypolyethoxyethanol
(Triton
X-114)
[22]
Drinking
water
sample
Tablets
of
different
pharmaceutical
containing
Vitamin
B12
Tap,
river
and
sea
water
Electrothermal
atomic
absorption
spectrometry
(ETAAS)
FAAS
Laser
induced
thermal
lens
spectrometry
Al
and
Zn
8-hydroxyquinoline,
Triton
X-114
[34]
Bottled
mineral
water
and
foodstuffs
Spectrofluorimetry
Cr
1-(2-pyridilazo)-2-naphtol
(PAN),
Triton
X-114
[73]
Chelating
agents,
ammonium
pyrrolidinedithiocarbamate
for
Cr(VI)
and
8-hydroxyquinoline
for
Cr(III),
Triton
X-114
[74]
Water
sample
contaminated
with
leather
effluents
River
water
and
sea
water
Flame
atomic
absorption
spectrometry
Flame
atomic
absorption
spectrometry
Cd
APDC
(0.5%,
m/v),
TX114
(5%,
v/v)
[75–
79]
Pyridyl-azo-naphthol
(PAN),
Triton
X-
114
[85]
Triton
X-114,
dithizone
[86]
Ion-associated
complex
in
the
presence
of
iodide
and
methyl
green
(MG),
[36]
Ammonium
pyrrolidinedithiocarbamate
(APDC)
solution
and
a
Triton
X-114
[87]
Urine
sample
Soft
drinks
Rice
and
water
sample
Certified
reference
rice
sample
and
food
samples
Urine
and
water
sample
AAS
(TS-FF-AAS)
Fluorescence
spectrometry
and
TS-FF-
AAS
Flame
atomic
absorption
spectrometry
Thermospray
flame
quartz
furnace
atomic
absorption
spectrometry
V
1-(2-pyridylazo)-2-naphthol
(PAN)
and
hydrogen
peroxide
in
acidic
medium,
Triton
X-100
[88]
Water
samples,
geological
samples
(FAAS)
Hg(II)
HgI
42
reacted
with
methyl
green
(MG)
cation,
octylphenoxypolyethoxyethanol
(Triton
X-114)
[81,89]
Ammonium
O,O-
diethyldithiophosphate
(DDTP),
Triton
X-114,
[90]
Triton
X-114,
1-(2-pyridylazo)-2-
naphthol
(PAN)
and
4-(2-thiazolylazo)
resorcinol
(TAR)
(chelating
agent)
[27]
1-(2-pyridylazo)-2-naphthol
(PAN),
Triton
X-114
[82]
Ammonium
O,O-
diethyldithiophosphate
(DDTP)
as
the
chelating
agent
and
0.3%
(m/v)
Triton
X-114
[83]
2-(5-bromo-2-pyridylazo)-5-
(diethylamino)-phenol
(5-Br-PADAP)
polyethyleneglycolmono-p-
nonyphenylether
(PONPE
7.5)
[84]
Sea
food
sample
Tap
wa
´ter
Water
samples
Natural
water
and
tilapia
muscle
samples
Human
hair,
dogfish
liver
and
dogfish
muscle
Hair
sample
ICP-OES
ICP-OES
Spectrophotometry
ICP-MS
CVAAS
ETAAS
Pb(II),
Co(II),
Cu(II)
1-Phenylthiosemicarbazide
(1-PTSC),
octylphenoxypolyethoxyethanol
(Triton
X-114)
[85]
Tap
water,
spring
water,
sea
water,
canned
fish,
black
tea,
green
tea,
tomato
sauce
and
honey
FAAS
Cd
and
Pb
Ammonium
O,O
diethyl
dithiophosphate
(DDTP)
(chelating
agent),
Triton
X-114
[86]
Urine
sample
(GF
AAS)
Fe
and
Cu
Eriochrome
Cyanine
R
(ECR),
Triton
X-
114
[36]
Bush,
branches
and
leaves;
water
samples
(mineral
and
sea
water)
and
food
samples
(vegetables,
bread
and
hazelnut)
FAAS
Cd,
Pb,
Cr,
Cu,
Zn,
Ni
and
Fe
Triton
X-114,
APDC
[87]
Environmental
samples
(FAAS)
and
(ICP-AES)
P.
Samaddar,
K.
Sen
/
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
1213

Author's personal copy
interference
of
Fe(III)
on
the
spectrophotometric
determination
of
Fe(II);
total
Fe
is
determined
by
flame
AAS.
The
results
obtained
reveal
that
this
method
is
an
alternative
approach
to
the
speciation
of
dissolved
iron
in
natural
waters
at
m
g
L
1
levels,
without
interferences.
The
ferrozine
reagent,
proposed
by
Stookey
[98],
reacts
with
Fe(II)
to
form
a
stable
magenta-colored
complex,
absorbing
at
562
nm
with
a
molar
absorption
coefficient
close
to
30,000
L
mol
1
cm
1
at
pH
between
4
and
9.
As
previously
discussed,
however,
Fe(III)
can
also
react
with
ferrozine,
and
therefore
interfere
with
the
determination
of
Fe(II).
Due
to
the
lack
of
a
highly
selective
masking
agent
for
Fe(II)
or
Fe(III)
against
each
other,
a
revision
of
the
classic
ferrozine
method
was
proposed
which
overcomes
interference
by
Fe(III)
[99].
In
this
method
a
mixture
of
dissolved
Fe(II)
and
Fe(III)
reacting
with
the
ferrozine
leads
to
the
absorbance
A
1
where,
e
Fe(II)
and
e
Fe(III)
are
the
molar
absorption
coefficients,
A
1
¼
e
FeðIIÞ
l
½FeðIIÞ
þ
e
FeðIIIÞ
l½FeðIIIÞ
(1)
and
[Fe(II)]
and
[Fe(III)]
are
the
concentrations
of
the
Fe
species.
After
addition
of
a
reducing
agent,
application
of
the
additive
property
of
the
Beer–Lambert
law
should
yield
the
absorbance:
A
2
¼
e
FeðIIÞ
lð½FeðIIÞ
þ
½FeðIIIÞÞ
(2)
Solution
of
the
simple
linear
system
of
Eqs.
(1)
and
(2)
gives
Table
2
(Continued
)
Element
Reagent
Sample
type
Method
of
detection
Fe(II)
2-(5-bromo-2-pyridylazo)-5-
diethylaminophenol
(5-Br-PADAP)
[37]
Beer
sample
Spectrophotometry
Mn
Laboratory
made
reagent
4-(5-bromo-
2_-thiazolylazo)orcinol
(Br-TAO)
and
the
surfactant
Triton
X-114
[88]
Food
sample
(rice
flour,
infant
formula
and
corn
flour),
biological
sample
(tomato
leaves)
Flame
atomic
absorption
spectrometry
(FAAS)
Mn
and
Fe
1-phenyl-3-methyl-4-benzoyl-5-
pyrazolone
(PMBP),
p-
octylpolyethyleneglycolphenylether
(Triton
X-100)
[89]
Water
sample
Graphite
furnace
atomic
absorption
spectrometry
Co
and
Ni
1-(2-pyridylazo)-2-naphthol
(PAN),
octylphenoxypolyethoxyethanol
(Triton
X-114)
[90]
Real
and
spiked
samples
Fiber
optic-linear
array
detection
spectrophotometry
Cu,
Ni,
Zn
and
Fe
2-(6-(1H-benzo[d]imidazol-2-
yl)pyridin-2-yl)-1Hbenzo[d]Imidazole
(BIYPYBI)
(complexing
agent),
Triton
X-
114
[91]
Blood,
orange
juice
and
lotus
tree
samples
FAAS
Table
4
Cloud
point
preconcentration
of
lanthanides
and
actinides.
Element
Reagent
Sample
type
Method
of
detection
U(VI)
Triton
X-114,
cethyl
trimethylammonium
bromide
(CTAB),
color
reaction
of
uranium
with
pyrocatechol
violet
in
the
presence
of
potassium
iodide
in
hexamethylenetetramine
buffer
media
[96]
Water
sample
(tap
water,
waste
water,
well
water
sample)
UV/vis
spectrometer
La(III),
Eu(III)
and
Lu(III)
Di(2-ethylhexyl)phosphoric
acid
and
Triton
X-100
[42]
Synthetic
aqueous
samples
ICP-AES
Zr
and
Hf
Quinalizarine
(chelating
agent),
Triton
X-114
[43]
Water
and
alloy
samples
ICP-AES
La(III),
Gd(III)
and
Yb(III)
p-sulfonato
thiacalixarene
(ST),
tetra-sulfonatomethylated
calix[4]resorcinarene
(SR),
calix[4]resorcinarene
phosphonic
acid
(PhR)
as
chelating
agents,
Triton
X-100
[44]
Synthetic
aqueous
samples
Spectrophotometry
U(VI),
Th(IV),
Zr(IV),
Hf(IV)
Dibenzoylmethane(DBM),
Triton
X-114
[45]
Synthetic
aqueous
samples
ICP-AES
Table
3
Cloud
point
preconcentration
of
representative
elements.
Element
Reagent
Sample
type
Method
of
detection
As(III)
APDC,
Triton
X-114
[92]
Pyronine
B,
sodium
dodecyl
sulfate
(SDS),
polyethylene
glycol
tert-
octylphenyl
ether
(Triton
X-114)
[30]
Ground
water
samples
Drinking
water
and
tap
water
samples
(ETAAS)
(HGAAS)
Sn
p-octyl
polyethyleneglycolphenyl
ether
(Triton
X-100)
and
sodium
dodecyl
sulfate
(SDS)
[93]
Water
sample
(GFAAS)
Sn(II)
and
Sn(IV)
a
polyoxometalate
(Triton
X-100),
CTAB
[63]
Various
alloy,
juice
fruit,
tape
and
waste
water
samples
Flame
atomic
absorption
spectrometry
(FAAS)
Al(III)
Xylidyl
Blue
(XB),
Triton
X-114,
[28]
Mineral
water
Flame
atomic
absorption
spectrometry
(FAAS)
Bi
Triton
X-100,
Octanol
(revulsant
and
synergic
reagent)
[94]
Water
and
geological
samples
Flame
atomic
absorption
spectrometry
(FAAS)
Pb
Triton
X-114,
octanol
(cloud
point
revulsant
and
synergic
reagent)
[25]
Tap
water,
river
and
lake
water
FAAS
Cr(III),
Pb(II),
Cu(II),
Ni(II),
Bi(III),
and
Cd(II)
Tween
80
[95]
Reference
material
and
spiked
samples
FAAS
Be(II)
1,8-dihydroxyanthrone
as
chelating
agent,
Triton
X-114
[41]
Water
samples.
Inductively
coupled
plasma-atomic
emission
spectrometry
(ICP-AES)
P.
Samaddar,
K.
Sen
/
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
1214

Author's personal copy
Fe
IIð
Þ½

¼A
1
e
Fe
IIð
Þ

A
2
e
Fe
IIIð
Þ
e
Fe
IIð
Þ
e
Fe
IIð
Þ

e
Fe
IIIð
Þ

l
Fe
IIIð
Þ½

¼A
2

A
1
e
Fe
IIð
Þ

e
Fe
IIIð
Þ

l
A
surfactant
concentration
of
1–1.5
g
L
1
was
found
to
extract
the
complexes
of
the
iron
species
effectively
[100].
Another
CPE
based
separation
and
spectrophotometric
detec-
tion
method
for
iron
was
proposed
by
Filik
and
Giray
[37].
In
this
method,
Fe(II)
reacts
with
2-(5-bromo-2-pyridylazo)-5-diethyla-
minophenol
(5-Br-PADAP)
in
the
presence
of
EDTA
yielding
a
hydrophobic
complex,
which
then
is
extracted
into
surfactant-rich
phase.
Total
iron
was
determined
after
the
reduction
of
Fe(III)
to
Fe(II)
by
using
ascorbic
acid
as
reducing
agent.
Variable
parameters
affecting
the
CPE
efficiency
were
evaluated
and
optimized.
The
proposed
method
was
applied
to
the
speciation
of
iron
in
beer
samples
with
satisfactory
results.
CPE
was
used
as
a
separation
and
preconcentration
step
combined
with
UV–vis
spectrophotometry
for
the
speciation
of
iron
in
beer
without
sample
digestion.
6.2.
Mercury
A
cloud
point
extraction
methodology
was
developed
for
simultaneous
preconcentration
of
Hg(II),
methylmercury
(MeHg),
ethylmercury
(EtHg),
and
phenylmercury
(PhHg)
was
developed
using
cold
vapor
atomic
fluorescence
spectrometry
for
speciation
analysis
of
mercury
in
fish.
The
four
mercury
species
were
taken
into
complexes
with
ammonium
pyrrolidine
dithiocarbamate
(APDC)
in
aqueous
non-ionic
surfactant
Triton
X-114
medium
and
concentrated
in
the
surfactant-rich
phase
by
heating
to
40
8C.
Separation
of
the
enriched
complexes
was
achieved
on
an
RP-C18
column
with
a
mixture
of
methanol,
acetonitrile,
and
water
(65:15:20,
v/v)
containing
200
mmol
L
1
acetic
acid
(pH
3.5)
as
the
mobile
phase.
An
on-line
oxidation
of
the
effluent
from
HPLC
was
done
in
the
presence
of
K
2
S
2
O
8
in
HCl,
prior
to
optimal
cold
vapor
generation
of
mercury
species.
The
variables
affecting
the
complexation
and
extraction
steps
were
examined.
The
precon-
centration
of
10
mL
of
solution
with
0.08%
w/v
Triton
X-114
and
0.04%
w/v
APDC
at
pH
3.5
gave
enrichment
factors
of
29,
43,
80,
and
98
for
MeHg,
EtHg,
PhHg,
and
Hg(II),
respectively.
The
developed
method
was
successfully
applied
to
the
speciation
of
mercury
in
real
fish
samples
[101].
A
dual-cloud
point
extraction
(dCPE)
technique
was
proposed
for
the
sample
pretreatment
of
capillary
electrophoresis
(CE)
speciation
analysis
of
mercury.
In
dCPE,
cloud
point
was
carried
out
twice
in
a
sample
pretreatment.
First,
four
mercury
species,
methylmercury
(MeHg),
ethylmercury
(EtHg),
phenylmercury
(PhHg),
and
inorganic
mercury
(Hg(II))
formed
hydrophobic
complexes
with
1-(2-pyridylazo)-2-naphthol
(PAN).
After
heating
and
centrifuging,
the
complexes
were
extracted
into
the
surfac-
tant-rich
phase.
Instead
of
the
direct
injection
or
analysis,
the
surfactant-rich
phase
containing
the
four
Hg
species
was
treated
with
150
m
L
0.1%
(m/v)
L
-cysteine
aqueous
solution.
The
four
Hg
species
were
then
transferred
back
into
aqueous
phase
by
forming
hydrophilic
Hg–
L
-cysteine
complexes.
After
dCPE,
the
aqueous
phase
containing
the
complexes
was
subjected
to
capillary
electrophoresis
(CE).
With
CE
separation
and
on-line
UV
detection,
the
detection
limits
were
45.2,
47.5,
4.1,
and
10.0
m
g
L
1
(as
Hg)
for
EtHg,
MeHg,
PhHg,
and
Hg(II),
respectively.
As
an
analysis
method,
the
present
dCPE–CE
with
UV
detection
obtained
similar
detection
limits
as
of
some
CE–inductively
coupled
plasma
mass
spectrom-
etry
(ICP-MS)
hyphenation
technique,
but
with
simple
instrumen-
tal
setup
and
obviously
low
costs.
Its
utilization
for
Hg
speciation
was
validated
by
the
analysis
of
the
spiked
natural
water
and
tilapia
muscle
samples
[82].
A
sensitive
method
for
speciation
analysis
of
inorganic
mercury
(Hg
2+
)
and
methyl
mercury
(MeHg
+
)
was
developed
by
using
high
performance
liquid
chromatography
(HPLC)
combined
with
inductively
coupled
plasma
mass
spectrometry
(ICP-MS)
after
cloud
point
extraction.
The
analytes
were
complexed
with
sodium
diethyldithiocarbamate
(DDTC)
and
preconcentrated
by
a
non-ionic
surfactant
Triton
X-114.
Mercury
species
were
effec-
tively
separated
by
HPLC
in
less
than
6
min.
The
enhancement
factors
for
25
mL
sample
solution
were
42
and
21,
and
the
limits
of
detection
were
4
and
10
ng
L
1
for
Hg
2+
and
MeHg
+
,
respectively
[102].
A
nonchromatographic
speciation
technique
for
mercury
was
developed
by
sequential
cloud
point
extraction
(CPE)
combined
with
inductively
coupled
plasma
optical
emission
spectrometry
(ICP-OES).
Hg
2+
was
complexed
with
I

to
form
HgI
42
which
reacted
with
the
methyl
green
(MG)
cation
to
form
hydrophobic
ion-associated
complex.
The
complex
was
then
extracted
into
the
surfactant-rich
phase,
which
are
subsequently
separated
from
methylmercury
(MeHg
+
)
in
the
initial
solution
by
centrifugation.
The
surfactant-rich
phase
containing
Hg(II)
was
diluted
with
0.5
mol
L
1
HNO
3
for
ICP-OES
determination.
The
supernatant
was
subjected
to
the
similar
CPE
procedure
for
the
preconcentration
of
MeHg
+
by
the
addition
of
a
chelating
agent,
ammonium
pyrrolidine
dithiocarbamate
(APDC),
in
order
to
form
water-insoluble
complex
with
MeHg
+
.
The
mercury
species
in
the
micelles
was
directly
analyzed
after
disposal
as
describe
above.
The
developed
technique
was
applied
to
the
speciation
of
mercury
in
real
seafood
samples
and
the
recoveries
for
spiked
samples
were
found
to
be
in
the
range
of
93.2–108.7%.
For
validation,
a
certified
reference
material
of
DORM-2
(dogfish
muscle)
was
analyzed
and
the
determined
values
were
in
good
agreement
with
the
certified
values
[80].
6.3.
Chromium
The
potential
of
polymerized
vesicle
coacervates
made
up
of
(4-
carboxybenzyl)bis[2-(10-undecenoyloxy)ethyl]methylammo-
nium
bromide
surfactants
for
the
extraction
of
chromium
species
Table
5
Cloud
point
preconcentration
of
precious
metals.
Element
Reagent
Sample
type
Method
of
detection
Au
O,O-diethyldithiophosphate
and
Triton
X-114
[97]
Certified
reference
human
hair
samples
Electrothermal
Vaporization
inductively
coupled
plasma
mass
spectrometry
Fig.
3.
The
percentage
use
of
different
metal
ions
for
cloud
point
extraction.
P.
Samaddar,
K.
Sen
/
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
1215

Author's personal copy
from
natural
waters
was
examined.
Linearly
linked
polymerized
vesicles
of
(4-carboxybenzyl)bis[2-(10-undecenoyloxy)
ethyl]-
methylammonium
bromide
monomer
were
prepared
by
UV
excitation,
and
several
factors
affecting
their
phase
behavior
were
investigated.
Evidently,
the
permeation
of
metallic
elements
through
the
polymeric
membrane
was
found
to
be
sensitive
to
ionic
radius
excluding
ions
larger
than
the
interbilayer
space
of
the
vesicle
assembly.
To
this
effect,
Cr
3+
ions
could
selectively
diffuse
through
the
polymeric
membrane.
At
the
same
time,
this
minimum
positive
charge
acts
synergistically
to
the
low
perme-
ability
of
the
bulky
CrO
42
anions
by
minimizing
electrostatic
attraction
with
the
bulky
CH
3
N
+
group.
Optimization
of
vesicle
structure
and
surface
charge
were
the
regulating
parameters
in
exploiting
this
unique
feature
toward
the
analytical
speciation
of
Cr
in
natural
waters.
Detection
limits
as
low
as
0.1
m
g
L
1
were
achieved
by
preconcentrating
only
10
mL
of
sample
volume
with
recoveries
in
the
range
of
97.0–105.5%
[103].
A
simple
mixed-micelle
cloud
point
extraction
procedure
was
developed
for
speciation
analysis
of
chromium
in
water
samples
by
electrothermal
atomic
absorption
spectrometry
(ET-AAS).
A
mixed
micelle
consisting
of
sodium
dodecyl
sulfate
(SDS)
and
Triton
X-
114
was
used
as
an
extracting
agent.
Cr(VI)
was
complexed
with
1,5-diphenyl
carbazide
(DPC)
in
an
HCl
medium
and
it
was
concentrated
in
the
surfactant-rich
phase
after
CPE.
Total
chromium
was
subjected
to
a
similar
extraction
procedure
after
oxidation.
Then
Cr(III)
concentration
was
calculated
by
subtracting
Cr(VI)
from
the
total
chromium.
Under
optimum
conditions,
a
detection
limit
of
1
ng
L
1
with
preconcentration
factor
of
92
was
achieved.
Also
the
relative
standard
deviation
for
five
replicate
determinations
of
0.1
m
g
L
1
Cr(VI)
was
3.5%.
The
proposed
method
was
successfully
applied
to
speciation
of
Cr(III)
and
Cr(VI)
in
environmental
water
samples
[104].
A
CPE
separation
method
was
coupled
with
electrothermal
vaporization
inductively
coupled
plasma
optical
emission
spec-
trometry
(ETV-ICP-OES)
detection
was
proposed
for
the
determi-
nation
of
chromium
species.
Thenoyltrifluoracetone
(TTA)
was
used
both
as
an
extractant
for
CPE
of
Cr(III)
and
a
chemical
modifier
for
ETV-ICP-OES
determination.
When
the
system
temperature
was
higher
than
the
cloud
point
temperature
(CPT)
of
the
selected
surfactant,
Triton
X-114,
the
complex
of
Cr(III)
with
TTA
could
enter
the
surfactant-rich
phase,
whereas
the
Cr(VI)
remained
in
aqueous
solutions.
Thus,
an
in
situ
separation
of
Cr(III)
and
Cr(VI)
could
be
realized.
The
concentrated
analyte
was
introduced
into
ETV-ICP-OES
for
determination
of
Cr(III)
after
proper
disposal.
Cr(VI)
is
reduced
to
Cr(III)
prior
to
determining
total
Cr,
and
its
assay
was
based
on
subtracting
of
Cr(III)
from
total
chromium.
The
proposed
method
was
applied
to
the
speciation
of
chromium
in
different
water
samples.
In
order
to
verify
the
accuracy
of
the
method,
a
certified
reference
water
sample
was
analyzed,
and
the
results
obtained
were
in
good
agreement
with
certified
values
[105].
CPE
based
speciation
of
chromium
in
water
samples
were
determined
by
flame
atomic
absorption
spectrometry.
Several
chelators
have
been
used
for
this.
Cr(III)
reacts
with
acetylacetone
yielding
a
hydrophobic
complex,
which
was
entrapped
in
the
Triton
X-100
surfactant-rich
phase,
whereas
Cr(VI)
remained
in
aqueous
phase.
Thus,
separation
of
Cr(III)
and
Cr(VI)
could
be
realized.
Total
chromium
was
determined
after
the
reduction
of
Cr(VI)
to
Cr(III)
by
using
ascorbic
acid
as
reducing
reagent.
Under
the
optimal
conditions,
the
detection
limit
of
this
method
for
Cr(III)
was
0.32
ng
mL
1
with
an
enrichment
factor
of
35
[106].
A
preconcentrative
separation
of
Cr(III)
species
from
Cr(VI)
by
CPE
is
also
possible
using
diethyldithiocarbamate
(DDTC),
bis-[2-Hy-
droxy-1-naphthaldehyde]
thiourea,
PAN,
TAN
8-hydroxyquinoline
or
1-phenyl-3-methyl-4-benzoylpyrazol-5-one
(PMBP)
as
the
chelating
agent
[73,107–111].
6.4.
Arsenic
Reaction
of
As(V)
with
molybdate
forms
a
yellow
heteropoly
acid
complex
in
sulfuric
acid
medium.
When
this
solution
is
taken
in
a
surfactant
medium
and
heated
to
55
8C,
analytes
are
quantitatively
extracted
to
the
non-ionic
surfactant-rich
phase
(Triton
X-114)
after
centrifugation.
To
decrease
the
viscosity
of
the
extract
and
to
allow
its
removal
methanol
was
added
to
the
surfactant-rich
phase.
20
m
L
of
this
solution
with
10
m
L
of
0.1%
m/v
Pd(NO
3
)
2
were
injected
into
the
graphite
tube
and
the
analyte
determined
by
electrothermal
atomic
absorption
spectrometry.
Total
inorganic
As(III,V)
was
extracted
similarly
after
oxidation
of
As(III)
to
As(V)
with
KMnO
4
.
As(III)
was
calculated
by
difference.
After
optimization
of
the
extraction
condition
and
the
instrumen-
tal
parameters,
a
detection
limit
(3
s
B)
of
0.01
m
g
L
1
with
enrichment
factor
of
52.5
was
achieved
for
only
10
mL
of
sample.
Relative
standard
deviations
were
lower
than
5%.
The
method
was
successfully
applied
to
the
determination
of
As(III)
and
As(V)
in
tap
water
and
total
arsenic
in
biological
samples
(hair
and
nail)
[112].
6.5.
Antimony
A
simple,
sensitive
method
for
the
speciation
of
inorganic
antimony
by
cloud
point
extraction
combined
with
electrothermal
atomic
absorption
spectrometry
(ETAAS)
was
evaluated
by
Jiang
et
al.
A
hydrophobic
complex
of
antimony(III)
was
prepared
with
ammonium
pyrrolidine
dithiocarbamate
(APDC)
at
pH
5.0
and
subsequently
the
hydrophobic
complex
enters
into
surfactant-rich
phase,
whereas
antimony(V)
remains
in
aqueous
solutions.
Antimony(III)
in
surfactant-rich
phase
was
analyzed
by
ETAAS
after
dilution
by
0.2
mL
nitric
acid
in
methanol
(0.1
M),
and
antimony(V)
was
calculated
by
subtracting
antimony(III)
from
the
total
antimony
after
reducing
antimony(V)
to
antimony(III)
by
L
-
cysteine.
The
detection
limit
of
the
proposed
method
was
0.02
ng
mL
1
for
antimony(III),
and
the
relative
standard
deviation
was
7.8%.
The
proposed
method
was
successfully
applied
to
speciation
of
inorganic
antimony
in
the
leaching
solutions
of
different
food
packaging
materials
with
satisfactory
results
[113].
A
flame
atomic
absorption
spectrometry
(FAAS)
determination
of
antimony
species
after
preconcentration
by
CPE
was
developed.
When
the
temperature
was
higher
than
the
cloud
point
extraction
temperature,
the
complex
of
antimony(III)
with
N-benzoyl-N-
phenylhydroxylamine
(BPHA)
can
enter
the
surfactant-rich
phase,
whereas
the
antimony(V)
remains
in
the
aqueous
phase.
Anti-
mony(III)
in
surfactant-rich
phase
was
analyzed
by
FAAS
and
antimony(V)
was
calculated
by
subtracting
of
antimony(III)
from
the
total
antimony
after
reducing
antimony(V)
to
antimony(III)
by
L
-cysteine.
The
proposed
method
was
applied
to
the
speciation
of
antimony
species
in
artificial
seawater
and
wastewater,
and
recoveries
in
the
range
of
95.3–106%
were
obtained
by
spiking
real
samples
[114].
Another
Sb
speciation
by
on-line
cloud
point
extraction
combined
with
electrothermal
vaporization
inductively
coupled
plasma
atomic
emission
spectrometry
(ETV-ICP-AES)
was
reported.
The
method
is
based
on
the
complexation
of
Sb(III)
with
pyrrolidine
thiocarbamate
(PDC)
which
form
an
hydrophobic
complex
at
pH
5.5
and
subsequently
enter
surfactant-rich
phase
at
pH
5.5,
whereas
Sb(V)
remain
in
aqueous
solutions.
The
preconcentration
step
is
mediated
by
micelles
of
the
non-ionic
surfactant
Triton
X-114
with
ammonium
pyrrolidine
dithiocarba-
mate
(APDC).
The
micellar
system
containing
the
complex
was
subjected
to
FIA
and
the
surfactant-rich
phase
was
retained
in
a
microcolumn
packed
with
absorbent
cotton,
at
pH
5.5.
After
the
surfactant-rich
phase
was
eluted
with
acetonitrile,
it
was
determined
by
ETV-ICP-AES.
Sb(V)
was
reduced
to
Sb(III)
by
L
-cysteine
prior
to
determination
of
total
Sb,
and
its
assay
is
based
P.
Samaddar,
K.
Sen
/
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
1216

Author's personal copy
on
subtracting
Sb(III)
from
total
antimony.
The
proposed
method
was
successfully
applied
for
the
speciation
of
inorganic
antimony
in
different
water
samples
and
urine
sample
with
satisfactory
results
[115].
6.6.
Selenium
Cloud
point
extraction
method
for
the
separation
and
precon-
centration
of
Se(IV)
and
Se(VI)
in
environmental
water
samples
as
well
as
total
selenium
in
animal
blood
and
tissue
samples
was
developed
by
Sounderajan
and
Udas.
3,3
0
-Diaminobenzidine
(DAB)
is
a
selective
and
sensitive
reagent
and
is
known
to
form
an
intense
yellow
compound
piazselenol
with
selenium(IV).
When
a
system
consisting
of
selenium,
DAB
and
surfactant
Triton
X-114
is
warmed
above
the
cloud
point
of
the
surfactant,
the
DAB–Se(IV)
complex
gets
extracted
into
the
surfactant-rich
phase
while
the
Se(VI)
remains
in
the
aqueous
phase.
Se(VI)
in
the
sample
was
reduced
to
Se(IV)
by
microwave
heating
of
solution
in
4
mol
L
1
HCl
and
total
Se
was
estimated
by
carrying
out
the
CPE.
The
quantification
of
selenium
was
carried
out
using
ETAAS.
The
detection
limit
of
selenium
in
environmental
water
samples
was
0.0025
m
g
L
1
with
an
enrich-
ment
factor
of
100.
The
proposed
method
was
successfully
applied
to
the
determination
of
selenium(IV),
(VI)
in
environmental
water
samples
and
determination
of
total
selenium
in
human
blood,
animal
blood
and
fish
tissue
[116].
A
fluorometric
ligand,
2,3-diaminonaphtalene
(DAN)
was
used
for
extraction
of
trace
amounts
of
organic
and
inorganic
selenium
species
prior
to
their
determination
by
spectrofluorimetry.
CPE
parameters
affecting
complexation
and
phase
separation
were
optimized.
The
limit
of
detection
was
calculated
by
using
nine
replicate
measurements
of
0.020
mg
L
1
Se
solution
after
com-
plexing
with
DAN
and
10-fold
CPE
preconcentration
was
2.1
m
g
L
1
.
The
suggested
method
could
be
used
for
selenium
species
of
selenite,
selenate,
and
total
organic
selenium
at
m
g
L
1
level
[117].
CPE
separation
followed
by
electrothermal
vaporization
induc-
tively
coupled
plasma
mass
spectrometry
(ETV-ICP-MS)
detection
was
proposed
for
the
speciation
of
inorganic
selenium
in
environmental
waters.
When
the
temperature
of
the
system
is
higher
than
the
cloud
point
temperature
(CPT)
of
the
selected
surfactant
Triton
X-114,
the
complex
of
Se(IV)
with
ammonium
pyrrolidine
dithiocarbamate
(APDC)
gets
extracted
into
the
surfactant-rich
phase,
whereas
the
Se(VI)
remains
in
aqueous
solutions.
Thus,
an
in
situ
separation
of
Se(IV)
and
Se(VI)
could
be
realized.
The
concentrated
analyte
was
introduced
into
the
ETV-
ICP
mass
spectrometer
for
determination
of
Se(IV)
after
dilution
with
200
mL
methanol.
Se(VI)
was
reduced
to
Se(IV)
prior
to
determining
total
selenium,
and
its
assay
was
based
on
subtracting
Se(IV)
from
total
selenium.
Under
the
optimized
experimental
conditions,
the
limit
of
detection
(LOD)
for
Se(IV)
was
8.0
ng
L
1
with
an
enhancement
factor
of
39
when
10
mL
of
sample
solution
was
preconcentrated
to
0.2
mL.
The
proposed
method
was
applied
to
the
speciation
of
inorganic
selenium
in
different
environmental
water
samples
with
the
recovery
for
the
spiked
samples
in
the
range
of
82–102%
[118].
6.7.
Manganese
The
speciation
of
Mn(II)
in
tea
infusion
was
studied
using
CPE.
In
tea
infusion,
the
flavonoid
bound
Mn(II)
was
extracted
at
pH
5.0
using
0.2%
(v/v)
Triton
X-100.
The
remaining
free
aquated
Mn(II)
and
weakly
complexed
Mn(II)
in
solution
were
both
chelated
with
8-hydroxyquinoline
(HOx)
and
CPE
preconcentrated
with
TX-100.
The
enriched
analyte
was
determined
by
flame
AAS.
The
method
was
not
essentially
affected
from
common
ions,
and
was
capable
of
Mn
speciation
in
tea
infusion
by
distinguishing
free
aquated
and
weakly
complexed
(unbound)
Mn(II)
from
flavonoid
bound
Mn(II)
fractions.
This
speciation
analysis
with
sequential
CPE
showed
that
about
30%
of
total
manganese
in
tea
leaves
was
total
chelatable
Mn
passing
into
tea
infusion,
and
that
about
95%
of
this
chelatable
Mn
was
in
the
unbound
state,
existing
primarily
as
inorganic
Mn(II)
species
[119].
6.8.
Tin
CPE
separation
and
graphite
furnace
atomic
absorption
spectrometry
(GFAAS)
detection
was
proposed
for
the
determina-
tion
of
inorganic
tin
species.
When
the
system
temperature
is
higher
than
the
cloud
point
extraction
temperature
(CPT)
of
the
mixed
surfactant
of
p-octyl
polyethyleneglycolphenyl
ether
(Triton
X-100)
and
sodium
dodecyl
sulfate
(SDS),
a
PAN
complex
of
Sn(IV)
could
be
extracted
into
the
surfactant-rich
phase,
whereas
the
Sn(II)
remained
in
the
aqueous
phase.
Thus,
an
in
situ
separation
of
Sn(IV)
and
Sn(II)
could
be
achieved.
The
main
factors
affecting
the
cloud
point
extraction
were
investigated
systematically.
Under
the
optimized
conditions,
the
detection
limit
for
Sn(IV),
was
found
to
be
0.51
ng
mL
1
.
The
proposed
method
was
applied
to
the
speciation
analysis
of
tin
in
different
water
samples
and
the
recovery
of
total
Sn
was
in
the
range
of
98.9–
100.7%
[93].
6.9.
Thallium
Ultra-trace
speciation
analysis
of
thallium
in
environmental
water
samples
was
achieved
using
CPE
and
analyzed
by
inductively
coupled
plasma
mass
spectrometry
(ICP-MS).
A
mixed
micelle
consisting
of
sodium
dodecyl
sulfate
(SDS)
and
Triton
X-
114
was
used
as
a
chelating
as
well
as
an
extracting
agent.
Tl(III)–
DTPA
(diethylenetriaminepentaacetic
acid)
complex
in
an
HCl
medium
could
be
extracted
into
a
surfactant-rich
phase
in
the
presence
of
Tl(I).
The
Tl(I)
in
the
supernatant
is
subjected
to
a
similar
extraction
procedure
after
bromine
oxidation.
Ultrasoni-
cally
assisted
back-extraction
is
used
to
extract
the
Tl(III)
species
from
the
surfactant-rich
phase
into
a
small
volume
of
aqueous
L
-
cysteine.
The
preconcentration
factor
and
detection
limit
were
125
and
0.02
pg
mL
1
,
respectively.
The
procedure
was
validated
by
comparing
the
sum
of
the
concentrations
of
individual
Tl
species
with
total
thallium
concentration
in
certified
reference
materials
[120].
7.
Future
perspectives
Keeping
in
view
the
large
number
of
CPE
procedures
for
metal
ions
and
metalloids
available,
it
is
noteworthy
to
have
preconcen-
tration
techniques
for
different
anionic
species
as
well.
The
diverse
properties
of
anionic
species
both
in
the
direction
of
its
usefulness
and
hazard
causing
effects
need
the
right
speciation
and
preconcentration
technique.
CPE
being
a
sustainable
method
is
worthy
of
performing
such
studies.
The
potential
of
CPE
lies
in
the
possibility
of
simultaneous
screening
for
a
number
of
anions
in
presence
of
metal
ions
in
complex
matrices.
The
inclusion
of
CPE
in
advanced
analytical
chemistry
courses
could
be
a
potential
future
trend
owing
to
the
various
aspects
that
may
be
discussed
when
a
CPE
experiment
is
demonstrated
(green
chemistry
principles,
elimination
of
organic
solvents
and
introduction
of
surfactants
in
spectroscopic
analysis,
trace
analysis,
the
physico-chemical
aspects
related
to
phase
separation,
etc).
8.
Concluding
remarks
As
a
general
conclusion
regarding
the
elemental
preconcentra-
tion
and
speciation
using
cloud
point
extraction
it
is
imperative
P.
Samaddar,
K.
Sen
/
Journal
of
Industrial
and
Engineering
Chemistry
20
(2014)
1209–1219
1217

Author's personal copy
that
the
method
is
devoid
of
using
toxic
solvents.
The
discussions
demonstrate
the
potential
of
this
impressive
micellar
phase
separation
technique.
Considering
the
high
preconcentration
efficiency,
versatility
and
low
cost
encountered
in
CPE,
it
is
expected
that
analytical
chemistry
will
flourish
to
a
large
extent
in
this
interesting
area,
not
only
in
the
field
of
analytical
applications
but
also
with
respect
to
basic
development
to
reach
complete
elucidation
for
phase
separation
behavior.
Acknowledgments
We
gratefully
acknowledge
University
Grants
Commission
(UGC,
Sanction
No.
41-248/2012
(SR))
for
funding.
One
of
the
authors,
Pallabi
Samaddar
expresses
sincere
thanks
to
the
UGC,
India
[Memo
No.
UGC/1228C/Major
Research
(SC)2012]
for
providing
necessary
fellowship.
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