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Determination of Cr(III) and total chromium in water samples by cloud point extraction and flame atomic absorption spectrometry
Abstract
A sensitive and selective method has been developed for the speciation of chromium in water samples based on cloud point extraction
(CPE) separation and preconcentration and determination by flame atomic absorption spectrometry. In the CPE method, Cr(III)
reacts with acetylacetone yielding a hydrophobic complex, which is 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, and the relative standard deviation was 3.4% (c = 100 ng mL−1, n = 7). The method has been applied to the speciation of chromium in natural water samples with satisfactory results.
... As a result, a precise and fast procedure for the recognition and detection of Cr +6 MIs is an urgent need. For this purpose, multiple analytical methods based on different techniques were established to trace the Cr +6 MIs in the natural environment and any particular system [4][5][6][7][8]. However, these procedures are time-consuming and require expensive instruments handled by well-trained individuals. ...
... As a result, a precise and fast procedure for the recognition and detection of Cr +6 MIs is an urgent need. For this purpose, multiple analytical methods based on different techniques were established to trace the Cr +6 MIs in the natural environment and any particular system [4][5][6][7][8]. However, these procedures are time-consuming and require expensive instruments handled by well-trained individuals. ...
... 6 Therefore, the detection and tracking of Cr(VI) concentration is important. There are various methodologies already available for detection of chromium and other heavy metal ions in general such as electrochemistry, 7 surface enhanced Raman scattering, 8 colorimetry, 9,10 atomic absorption spectrometry, 11 inductively coupled plasma mass spectrometry 12 etc. These methodologies are cumbersome and require costly instruments and proper setup. ...
This work involves fluorescent probe which is composed of carbon dots (CD) and cadmium sulfide quantum dots (CdS QD) for the sensitive and selective fluorescence detection of chromium(vi) ions. The blue fluorescent carbon dots were synthesized by hydrothermal method from natural precursor apricot. The carbon dots–cadmium sulfide quantum dots (CD–CdS QD) nanocomposite was synthesized and all as-synthesized products were characterized using different characterization techniques. It showed white fluorescence under UV light which was quenched selectively in the presence of chromium(vi) ions due to the inner filter effect (IFE). The linear decrease in the white fluorescence was observed in the concentration range 2–120 μM of chromium(vi) ions with the limit of detection 2.07 μM. This is novel probe for the sensitive, selective and rapid detection of chromium(vi) ions.
... Determination of Cr 3+ amount in those products using reliable and effective analytical techniques is necessary. The commonly used techniques for Cr 3+ measurement include atomic absorption spectrometry (AAS) [11,12], inductively coupled plasma-optical emission spectrometry (ICP-OES) [13], inductively coupled plasma -mass spectrometry (ICP-MS) [14], electrochemistry [15,16], and spectrophotometry [17,18]. Although various analytical techniques have been developed for Cr 3+ quantification, and most of the conventional methods offer high accuracy and sensitivity, they suffer from high costs and skills required to operate the instruments. ...
A facile method for trivalent chromium (Cr 3+) ion determination using optical silver nanoparticles capped carbon dots (Ag@CDs) was developed. The optical responses via absorption and fluorescence of Ag@CDs in the presence of Cr 3+ ion were detected. The nanocomposite showed maximum absorption wavelength at 406.0 nm, while emission wavelength appeared at 526.0 nm when excited at 406.0 nm. Optimal conditions for the Ag@CDs activity on Cr 3+ ion detection were at pH 6, volume ratio between Ag@CDs and Cr 3+ ion of 1.0:4.0, and reaction time of 20 min. The linearity range of the detection was 0.1-10.0 mg/L. In the absorption mode, the limit of detection (LOD) and limit of quantification (LOQ) were 0.10 mg/L and 0.31 mg/L, respectively. The fluorescence mode of detection showed LOD and LOQ of 0.06 mg/L and 0.18 mg/L, respectively. The dual-mode sensor was applied for Cr 3+ ion quantification in dietary supplement samples because it is an essential micronutrient and widely used as supplement products. The recovery study of the spiked sample extracts was in the range of 96.86-103.05 %. The results showed good agreement with those from a conventional method of atomic emission spectrometry. The optical changing mechanism of the nanocomposite could be explained by the electron transfer from Ag@CDs to Cr 3+ .
... [2][3][4] But when taken in excess, about 1 mg daily, it is harmful. 5,6 Alternative techniques, particularly spectrophotometry, 7 isotope dilution mass spectrometry, 8 cloud point extraction and ame atomic absorption spectrometry, 9 HPLC, 10 chromatography 10 inductively coupled plasma mass spectrometry, 11 have been considered for the monitoring of Cr(III) ions. Even though these techniques produced accurate, selective, and sensitive results, they are hindered by expensive, specialized gear besides laborious and time-consuming sample preparation. ...
Tetragonal zirconia (t-ZrO 2 ) nanoparticles (ionophore) are used in newly designed and improved ion selective electrodes for chromium ion detection as an alternative, low-cost, high-precision, and selectivity method.
... Presently, several conventional methods have been used for the detection of Fe 3+ , Cr 2 O 7 2− , and nitro-molecules, including chromatography [10] and electrochemical methods [11]. However, these methods inevitably have various problems, such as complex sample pretreatment, large amounts of organic solvents, easy secondary pollution, timeconsuming procedures, nonportable testing instruments, skilled operation, and high cost, which limit their application in routine analysis and detection. ...
The effective detection of environmental pollutants is very important to the sustainable development of human health and the environment. A luminescent Cd(II) coordination complex, {[Cd(dbtdb)(1,2,4-H3btc)]·0.5H2O}n (1) (dbtdb = 1-(2,3,5,6-tetramethyl-4-((2-(thiazol-4-yl)-2H-benzo[d]imidazol-3(3aH)-yl)methyl)benzyl)-2,7a-dihydro-2-(thiazol-4-yl)-1H-benzo[d]imidazole, 1,2,4-H3btc = 1,2,4-benzenetricarboxylic acid), was obtained by hydrothermal reactions. Complex 1 has a chain structure decorated with uncoordinated Lewis basic O and S donors and provides good sensing of Fe3+, Cr2O72-, and p-nitrophenol with fluorescence quenching through an energy transfer process. The calculated binding constants were 3.3 × 103 mol-1 for Fe3+, 2.36 × 104 mol-1 for Cr2O72-, and 9.3 × 103 mol-1 for p-nitrophenol, respectively. These results show that 1 is a rare multiresponsive sensory material for efficient detection of Fe3+, Cr2O72-, and p-nitrophenol.
... The studied dietary products could help adults to complete their K level. Similarly, the sodium-topotassium (Na/K) ratio is thought to be a predictor of cardiovascular disease (CVD) and blood pressure consequences [59][60][61][62]. The optimum Na/K ratio is 1.0, considered suitable for health Content courtesy of Springer Nature, terms of use apply. ...
The current work is aimed to assess the impact of macronutrient and mineral contents in food products of packaged food, restaurant food, and street food in Hyderabad. The estimated daily intake of macronutrients and minerals, followed by the toxic risk assessment of microminerals by consuming studied food dishes, was also conducted. The collected products were freeze-dried and standard procedures for measuring macronutrients were followed. At the same time, the acid digestion method was used to prepare the solution for detecting minerals by atomic absorption spectrometry. The resulting data indicated that all the food dishes supplied 134–454 kcals/100 g. The chicken/meat and pulse food dishes of all three categories were enriched with protein except bhindi masala. All the food dishes have a massive variation in fat contents and differ based on the used quantity of hydrogenated oil during their preparations. A significant difference in the macro- and microminerals in studied food products was observed. However, all food dishes are a good supplementary source of fundamental nutrients, supplying the recommended daily allowances for adults. The estimated hazardous index (Ih) of microminerals in some street and restaurant food products (based on a survey) showed possible toxicity risk, especially for the workers of automechanic workshops (Ih > 1.00). Thus, it is concluded that the contaminated (cheap) raw materials and unhygienic conditions for preparing street and restaurant foods and hawking places (atmospheric pollution) are the significant sources of micromineral contamination.
Graphical abstract
... Therefore, the sensitive and precise determination of UA is significant in, for instance, disease screening and physiological studies [5]. In recent years, many methods have been developed for the estimation and detection of UA levels, such as enzymatic assays [6,7], electrochemical sensors [8][9][10][11], spectrophotometric methods [12][13][14][15], Raman spectroscopy [16], chromatography [17][18][19], and fluorescent spectrometry [20][21][22][23][24]. Although enzymatic assays are the conventional method for the detection of UA, this method has challenges, including the high purification costs and the thermal instability of enzyme. ...
As an important biomarker in urine, the level of uric acid is of importance for human health. In this work, a Cu(II) functionalized metal–organic framework (Cu2+@Tb-MOFs) is designed and developed as a novel fluorescence probe for wide-range uric acid detection in human urine. The study shows that this fluorescence platform demonstrated excellent pH-independent stability, high water tolerance, and good thermal stability. Based on the strong interaction between metal ions and uric acid, the designed Cu2+@Tb-MOFs can be employed as efficient turn-on fluorescent probes for the detection of uric acid with wide detection range (0~104 µM) and high sensitivity (LOD = 0.65 µM). This probe also demonstrates an anti-interference property, as other species coexisted, and the possibility for recycling. The sensing mechanisms are further discussed at length. More importantly, we experimentally constructed a molecular logic gate operation based on this fluorescence probe for intelligent detection of uric acid. These results suggest the Cu(II) functionalized metal–organic framework can act as a prominent candidate for personalized monitoring of the concentration of uric acid in the human urine system.
... Literature survey discloses use of various reducing agents for reduction of highly toxic hexavalent chromium to relatively nontoxic trivalent chromium. [28][29][30] In the present case, ascorbic acid, hydroxylamine and hydrazine salt were used and optimized for reduction of Cr(VI). The inconvenience in getting sun light inside laboratory has prompted the use of reducing agent even in the case of sorption on TiO 2 even though it is known as a good photo catalyst. ...
Titanium dioxide (TiO 2), layered hydrazinium titanate (LHT) and eggshell were studied for sorption of chromium from aqueous streams. Among the three sorbents, the eggshell, a bio-waste is found to have maximum sorption capacity of 315 mg g −1. Sorption of Cr(III) as well as Cr(VI) was found to be spontaneous on LHT while TiO 2 and eggshell can accumulate only Cr(III). However, sorption of Cr(VI) on these was ensued after in situ reduction of Cr(VI) to Cr(III). Experimental result indicates absence of any interference from ions commonly present in ground water. ARTICLE HISTORY
... Arsenic, lead and chromium contents of fish liver, muscle, blood and river water Tissue contents of arsenic, lead and chromium were determined using an atomic absorption spectrometer (Perkin Elmer A Analyst 700). Elemental chromium was analyzed according to the method as suggested by Sun and Liang (2008). Tissue lead (Pb) content was measured by the method of Ghosh et al. (2013). ...
A comparative analysis was made on hematological, biochemical and oxidative stress indices in male spiny eel fish (Mastacembelus armatus) collected from two main rivers, the Haora and the Gomati Rivers of Tripura, a State of Northeast India, in relation to certain physiochemical properties of the waterbodies. It was revealed that total count of RBC, hematocrit, Hb, MCV and MCHC were significantly low in the Haora River fish samples. Significant differences in the biochemical variables were noted regarding tissue energy metabolism such as blood glucose level, liver and muscle glycogen contents, pyruvic acid level, free amino acid nitrogen, transaminase enzyme activities, tissue and serum protein contents, liver glucose 6-phosphatase activity and TCA cycle enzyme activities such as MDH, SDH and IDH. The water quality of the rivers was assessed in terms of pH, turbidity, total suspended solids, total dissolved solids, total alkalinity, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total hardness and heavy metal/metalloid concentration such as lead, cadmium, chromium and arsenic, which revealed that the Haora River was more polluted than the Gomati River. These might be involved in deterioration of body’s antioxidant defense system of the Eel fish of Haora River, as evidenced by depletion of tissue glutathione content, elevation of lipid peroxidation level and decreased antioxidant enzyme activities in the tissue samples of the studied fish. These suggested that poor water quality of the Haora River was supposed to be an important causative factor for more adverse toxicological effect on the spiny eel fish of that river.
... Tissue Cr (VI) content of brain tissue was determined using atomic absorption spectrometer (Perkin Elmer A Analyst 700) according to the method suggested by Sun and Liang [43]. Data were expressed as µg/g tissue. ...
Objective: Effect of oleanolic acid against hexavalent chromium-induced altered brain energy metabolism associated with oxidative stress was evaluated in the present study. Methods: Swiss albino mice were divided into three groups, Control (n=6), chromium-treated (n=6), and oleanolic acid (OA) supplemented (n=6). The chromium treated group was orally administered with K2Cr2O7 for 30 days at a dose of 10 mg/kg b.w/day. OA supplementation was given at a dose of 5 mg/kg bw/day for the past 14 days of chromium treatment. Control group received the vehicle only. After the treatment, whole brain was removed for examining the parameters such as pyruvic acid, free amino nitrogen, tissue protein, TCA cycle enzyme activities, NADH dehydrogenase function, and oxidative stress markers. Results: Significant decrease in cerebral pyruvic acid content associated with suppressed malate dehydrogenase and succinate dehydrogenase activities were observed. The NADH dehydrogenase activity was inhibited owing to enhanced accumulation of chromium in cerebral tissue. Depletion of proteins and increased free amino acid nitrogen were accompanied with inhibited cathepsin, pronase and trypsin activities, and increased transaminase function. In addition, GSH content was decreased along with increased lipid peroxidation, oxidized GSSG content, TG/GSSG ratio, carbonylated protein content, and tissue free hydroxyl radical formation. Superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase were also inhibited by hexavalent chromium. Oleanolic acid supplementation was found to have significant protective effect against brain metabolic and oxidative dysfunctions. Conclusion: The present study elucidated therapeutic efficacy of oleanolic acid against hexavalent chromium toxicity in brain tissue of mice.
... The determination of Cr and melamine has been achieved previously by spectroscopic, [18][19][20][21][22] chromatographic, 23 colorimetric, [24][25][26] and electrochemical [27][28][29] methods. Spectroscopic and mass spectrometry methods, such as inductively-coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectroscopy (AAS), involve sophisticated instrumentation, complex sample preparation, time consumption, and high cost. ...
The electrophoretic deposition (EPD) of citrate-stabilized Au nanoparticles (cit-Au NPs) occurs on indium tin oxide (ITO)-coated glass electrodes upon electrochemical oxidation of hydroquinone (HQ) due to the release of hydronium ions. Anodic stripping voltammetry (ASV) for Au oxidation allows the determination of the amount of Au NP deposition under a specific EPD potential and time. The binding of Cr3+ to the cit-Au NPs inhibits the EPD by inducing aggregation and/or reducing the negative charge, which could lower the effective NP concentration of the cit-Au NPs and/or lower the electrophoretic mobility. This lowers the Au oxidation charge in the ASV, which acts as an indirect signal for Cr3+. The binding of melamine to cit-Au NPs similarly leads to aggregation and/or lowers the negative charge, also resulting in reduction of the ASV Au oxidation peak. The decrease in Au oxidation charge measured by ASV increases linearly with increasing Cr3+ and melamine concentration. The limit of detection (LOD) for Cr3+ is 21.1 ppb and 16.0 ppb for 15.1 and 4.1 nm diameter cit-Au NPs, respectively. Improving the sensing conditions allows for as low as 1 ppb detection of Cr3+. The LOD for melamine is 45.7 ppb for 4.1 nm Au NPs.
... Therefore, it is crucially important to determine and monitor chromium level in industry and environment as well. Up to now, various analytical techniques have been reported for the Cr (III) determination such as ion chromatography (Michalski 2005), high-performance liquid chromatography (HPLC) (Kaur & Malik 2009), spectrophotometry (Kumar & Muthuselvi 2006;Zhao & Han 1994), atomic absorption spectroscopy (Sun & Liang 2008;Divrikli et al., 2008), fluorimetry (Elavarasi et al., 2014). But, the majority of these techniques have some limitations in terms of the properties such as needs of time-consuming, tedious and complex pretreatment processes sophisticated instruments, expert operators and expensive consumables. ...
Bu çalışmada, yeni sentezlenen iyonoforlar kullanılarak tümüyle katı-hal krom (III)-seçici potansiyometrik polivinil klorür (PVC) membran sensör geliştirildi. Bu amaçla yeni sentezlenen akriloil grup içeren (E)-4-(4-Nitro fenilimino) metil fenil akrilat (A1), (E)-4-(4-kloro fenilimino) metil fenil akrilat (A2) ve (E)-4-(4-hidroksibenzil dimino) benzoik asit akrilat (A3) schiff bazları iyonofor olarak kullanıldı. En uygun potansiyometrik özelliklere sahip membran bileşimi farklı oranlarda iyonoforlar (A1, A2 ve A3), plastikleştiriciler (o-nitrofeniloktil eter (o-NPOE)), bis (2-etilheksil) sebekat (DOS), dibutil ftalat (DBP) dioktil ftalat (DOP) ve PVC kullanılarak belirlendi. Ayrıca, potasyum tetrakisparaklorofenil borat (KTpClPB) ve sodyum tetrafenil borat (NaTPB) elektrotlarının doğrusal çalışma aralığına ve eğimine her onkat’lık iyon aktivitesi değişimine karşı etkisi de araştırıldı. Geliştirilen krom (III)-seçici sensör için % 1,0 A2 bileşiği, % 67,0 (a/a) o-NPOE ve % 32,0 (a/a) PVC oranları en uygun membran bileşimi olarak belirlendi. Geliştirilen krom (III)-seçici sensör pH 3,50’de 1,3×10-7−1,0×10-1 M konsantrasyon aralığında standart krom (III) iyon çözeltisine karşı doğrusal cevap sergiledi (R2= 0,9938). Sensör ile doğrusal çalışma aralığındaki her onkat’lık standart krom (III) konsantrasyon değişiminin ortalaması 27,12±0,81 mV’luk eğim değeri, tekrarlanabilir potansiyeller elde edildi. Geliştirilen tümüyle katı-hal krom (III)-seçici potansiyometrik PVC membran sensörün tayin limiti 6,3×10-8 M ve cevap süresi ≤10 s olarak belirlendi. Yaygın bazı katyon türlerinin geliştirilen sensör üzerindeki girişim etkileri incelendi. Önerilen sensörün analitik olarak kullanılıp kullanılamayacağını araştırmak için, gerçek numunelerde krom (III) iyonunun potansiyometrik tayini gerçekleştirildi. Elde edilen sonuçlar indüktif olarak eşleştirilmiş kütle spektrometresi (ICP-MS) metodu ile elde edilen verilerle istatiksel olarak karşılaştırıldı.
... 4,5 Over the past few decades, a few detection methods have been developed to determine trace amounts of Cr 3+ ions, such as inductively coupled plasma-atomic emission spectrometry (ICP-MS), electrochemical methods, colorimetric methods, spectrophotometry and atomic absorption spectrometry (AAS). [6][7][8][9][10][11][12] Compared with these technologies, luminescence detection has the characteristics of simple operation, short time and low cost, and has attracted widespread attention. However, currently reported probes still have huge limitations in terms of selectivity, sensitivity and the limit of detection (LOD). ...
Highly selective and sensitive, and low detection limit probes that can work in aqueous solution are of great significance for detection. Present here is a unique metal organic framework of...
... [7][8][9] Therefore, methods for the efficient detection of Cr 2 O 7 2À are urgent to be explored. Currently, several traditional methods have been developed for the determination of Zn 2+ , Fe 3+ and Cr 2 O 7 2À , such as atomic absorption spectrophotometry, [10][11][12] electrochemical methods, [13][14][15] and inductively coupled plasma mass spectrometry. [16][17][18] However, these methods are usually expensive, time-consuming, or require complicated sample preparation processes. ...
A luminescent Cd(ii) coordination polymer, namely {[Cd(btic)(phen)]·0.5H2O}n(CP-1) (H2btic = 5-(2-benzothiazolyl)isophthalic acid, phen = 1,10-phenanthroline), was constructed through the mixed-ligand method under solvothermal conditions. CP-1manifests a chain structure decorated with uncoordinated Lewis basic N and S donors. CP-1exhibits high sensing towards Zn²⁺, Fe³⁺and Cr2O7²⁻ions with fluorescence enhancement or quenching. CP-1exhibited a fluorescence enhancement for Zn²⁺ions through weak binding to S and N atoms, and a fluorescence quenching for Fe³⁺and Cr2O7²⁻ions by an energy transfer process. The binding constants were calculated as 1.812 × 10⁴mol⁻¹for Zn²⁺, 4.959 × 10⁴mol⁻¹for Fe³⁺and 1.793 × 10⁴mol⁻¹for Cr2O7²⁻. This study shows CP-1as a rare multi-responsive sensor material for the efficient detection of Zn²⁺, Fe³⁺and Cr2O7²⁻ions.
... Cr (VI) is quite mobile in soils due to its charge repulsion and solubility [4]. Moreover, it can induce carcinogenesis because of its ability to cross biological membranes easily and react with protein components and nucleic acids inside the cell [5]. In the natural environment, the presence of oxygen or manganese dioxide can oxidize Cr (III) to Cr (VI). ...
In most cases, direct X-ray fluorescence (XRF) analysis of solutions entails technical difficulties due to a high X-ray scattered background resulting in a spectrum with a poor signal-to-noise ratio (SNR). Key factors that determine the sensitivity of the method are the energy resolution of the detector and the amount of scattered radiation in the energy range of interest. Limiting the width of the primary spectrum by the use of secondary targets, or filters, can greatly improve the sensitivity for specific portions of the spectrum. This paper demonstrates a potential method for SNR optimization in direct XRF analysis of chromium (Cr) contamination. The suggested method requires minimal sample preparation and achieves higher sensitivity compared to existing direct XRF analysis. Two states of samples, fly ash and leachate from municipal solid waste incineration, were investigated. The effects of filter material, its absorption edge and filter thickness were analyzed using the combination of Monte Carlo N-Particle (MCNP) code and energy-dispersive XRF spectrometry. The applied filter removes primary photons with energies interfering with fluorescence photons from the element of interest, thus results in lower background scattering in the spectrum. The SNR of Cr peak increases with filter thickness and reaches a saturation value when further increased thickness only increases the measurement time. Measurements and simulations show that a Cu filter with a thickness between 100 μm and 140 μm is optimal for detecting Cr by taking into account both the SNR and the exposure time. With direct XRF analysis for solutions, the limit of quantitation (LOQ) of the achieved system was 0.32 mg/L for Cr, which is well below the allowed standard limitation for landfills in Sweden. This work shows that XRF can gain enough sensitivity for direct monitoring to certify that the Cr content in leachate is below environmental limits.
Polyaniline nanofibers PANI with titanium dioxide TiO2 Nano-composite are mainly utilized as surface plasmon resonance (SPR) sensor to discover two major types of chromium heavy metals in real surface water samples. Despite the fact that, Chromium (+ III and + VI) both ions are toxic, Cr (VI) is the most hazardous due to its higher water solubility”. The two ions were detected using plasmon sensing by monitoring the shift in the SPR resonance angle. The reason for the change in the SPR shift angle, It resulted from PANI’s abundance of amine and imine nitrogen groups. It is associated with the change from benzenoid to quinoid rings, which prolongs conjugation between neighboring rings in polymeric chains and offers high coordinating functions between the surface of NPs and chromium ions. That leads to enhanced the evanescent field that detects even a small variation in the refractive index. The calibration curve gave a high level of linearity in the range of 0.1–1 ppb is [0.411 Cr(III) + 0.026] and [0.410 Cr(VI) + 0.025]. Likewise, [0.039 Cr(III) + 0.001] and [0.039Cr(VI) + 0.001] for 1–15 ppb region. Both linearity ranges illustrate good response towards the chromium ion solutions. The limits of detection (LODs) for Cr(III) and Cr(VI) were found to be 0.1 ppb. The proposed SPR sensor toward toxic heavy metal could offer a new possibility for nonintrusive, fast, and reliable (LOD) SPR detection. For the purpose of determining the trace amounts of chromium present in surface water, industrial waste water, and vegetable samples, the suggested approach is found to be incredibly easy to use, quick, and sensitive.
It is very important to determine the presence of toxic Cr(VI) in aqueous environment. Detection of Cr(VI) using AuNPs has been carried out based on the oxidation or etching principle, which results in the change of localized surface plasmon resonance. In this work, the effects of size and concentration of colloidal AuNPs on the Cr(VI) sensing characteristics were studied by both simulation and experiment. In the simulation study using MNPBEM toolbox, the etching process was described as shrinking of AuNPs with total volume loss reflecting the concentration of Cr(VI) as oxidizing ions. The experiment was carried out by exposing colloidal AuNPs with different size and concentration to Cr(VI). The AuNPs were obtained from laser-induced photochemical process, in which aqueous solution of Au ions were subjected to femtosecond laser irradiation. The simulation results showed wider blue-shift of λLSPR per total volume loss when larger AuNPs were employed and higher intercept value of extinction decrease per total volume loss when more AuNPs were present in the system. Correspondingly, the experiment demonstrated more distinct color change and wider λLSPR per Cr(VI) concentration when larger AuNPs were used. More concentrated colloid showed still-red color after Cr(VI) etching, representing higher intercept value of extinction decrease per Cr(VI). Both simulation and experiment results show that, in etching-based Cr(VI) sensing, large AuNPs displayed wider LSPR wavelength shift compared to the small nanoparticles. On the other hand, concentration of AuNPs contributes to the intensity change and higher concentration of AuNPs offers higher Cr(VI) sensing range. This result provided an insight on how colorimetric sensor performance might be affected by the choice of nanoparticle size and concentration used in the system.
In this work, a novel mononuclear complex In(H2nha)3 (1) (H3nha=3-hydroxy-2-napthanoic hydroxamic acid) was synthesized and characterized. Single-crystal X-ray diffraction revealed that 1 shows a centrosymmetric structure consisting of one In(III)...
A simple, rapid, sensitive and inexpensive approach based on a combination of using solid phase extraction (SPE) of 8-hydroxyquinoline (8HQ) for speciation and preconcentration of Cr (III) and Cr (VI) in river water and direct determination of these species using a flow injection system with chemiluminescence detection (FI-CL) using 4-Diethyl Amino Phenyl Hydrazine (DEAPH)-hydrogen peroxide system, is described in this work. Because of the fact that at different pH, the two forms of chromium (Cr (III) and Cr (VI) has different exchange capacity on the 8HQ, therefore, two columns were constructed, and the pH of column 1 was adjusted at pH 3 for retaining Cr (III) and column 2 was adjusted at pH 1 for retaining of Cr (VI). The sorbed Cr (III) and Cr (VI) species were eluted from columns using 3.0 mL of 0.1 N of HCl and 3.0 mL of 0.1 N of NaOH, respectively. The flow injection-chemiluminescence (FI-CL) method is based on light emitted from oxidation of DEAPH by the H2 O2 in the presence of Cr (III) which catalyzes the reaction. The flow cell is a transparent coiled tube made from glass (2.0 x 4.0, inner and outer diameter) and located close to the photodetector. The flow parameters: flow rate, sample volume, flow cell length and distance to the CL detector were studied and optimized. Under optimum flow conditions, the Cr (III) concentration can be determined over the range of 5-350 μg L-1 with LOD of 1.2 μg L-1 since the concentration of Cr (III) is proportional to intensity of the CL signal. The RSD% for 10 and 50 μg L-1 of Cr (III) were 1.2% and 3.2 % respectively. The effects of Al (III), Cd (II), Zn (II), Hg (II), Pb (II), Co (II), Cu (II), Ni (II), Mn (II), Ca (II) and Fe (III) were investigated. The proposed method is highly selective and sensitive, enabling a rapid determination of Cr (III) amount in the presence of other interfering metals. Finally, the FI-CL method is examined in five river water samples with excellent recoveries.
In this work, we performed the cloud point extraction with low and high concentrations of Cu(II) and Cr(III), two particularly toxic metallic pollutants, that have been shown to have adverse effects on human health and the environment. Removal of the metal ions was achieved in the presence of Triton X-100 as a non-ionic surfactant and N,N′-bis(salicylidene)-thiocarbohydrazide as a chelating ligand in concentrated chloride medium. The behavior of the Schiff base was initially investigated in homogeneous DMSO-water and micellar Triton X-100-water media. The obtained values of the acid constants show that the extractant is more acidic in micellar media than in pure aqueous medium. The recorded cloud point temperatures of Triton X-100 are significantly impacted by the sodium chloride concentration, the surfactant concentration, and the Schiff base ligand. Under the optimised experimental conditions, a quantitative extraction of Cu(II) and a maximum extraction rate of 74 % of Cr(III) were obtained. The reduction of the metal concentration from 10 ⁻³ mol L ⁻¹ to 10 ⁻⁶ mol L ⁻¹ resulted in a reduction of the temperature by 10 °C and a reduction of the contact time from 10 h to 3 h.
Background
Ionophores in the composition of potentiometric ion‐selective electrodes interact directly with the analyte ion and enable the determination of ionic species in various samples.
Objectives
In this study, a novel ion‐selective electrode based on 5‐bromosalicylaldehyde thiosemicarbazone was developed for the selective determination of Cr ³⁺ ions.
Methods
The optimum electrode composition contained ionophore, poly (vinyl chloride) (PVC), bis (2‐ethylhexyl) sebacate (BEHS) and potassium tetrakis ( p ‐chlorophenyl) borate (KT p ClPB) in ratios of 4.0: 61.0: 34.0: 1.0 (mg), respectively. Potential measurements were performed using a computer‐controlled multi‐channel potentiometric measurement system.
Results
The developed Cr (III)‐selective electrode exhibited a low detection limit of 3.96 × 10 ⁻⁶ M over a wide concentration range of 1.0 × 10 ⁻⁵ – 1.0 × 10 ⁻¹ M ( R ² : 0.9979). The electrode exhibited good selectivity towards Cr ³⁺ ions among metal ions with different charges. The chromium (III)‐selective electrode, which exhibited highly reproducible results in three different concentration ranges, also had a very fast response time of 5 s.
Conclusions
The developed Cr (III)‐selective electrode were successfully performed in various beverage samples. As a result, the proposed electrode can be an alternative to other analytical methods in the analysis of Cr ³⁺ ions.
Hexavalent chromium (Cr(VI)) is highly carcinogenic and mutagenic, which is seriously harmful to human health. Hence, it is important to create a probe that can detect Cr(VI) effectively. In this work, gold nanotetrapods (Au NTPs) were applied in colorimetric detection for the first time. Based on the oxidative etching principle of Cr(VI) on Au NTPs, a sensitive and multicolor response detection method for Cr(VI) was established. The oxidative etching of Au NTPs by Cr(VI) resulted in the blue shift of plasmon resonance absorption peak of Au NTPs with the change of morphology. As the etching progress processed, Au NTPs solution exhibited obvious color changes from gray-green to blue-violet and then to pink. This multicolor response design is very convenient for naked-eye detection. The limit of detection (LOD) of Cr(VI) is 3 nM for the naked eyes and 0.5 nM for UV-vis spectrum, both of which are lower than the toxicity level of Cr(VI) (0.2 μM) set by United States Environmental Protection Agency. This sensing method exhibits good linearity between the wavelength shift and Cr(VI) concentration in the range of 0.5 nM to 8 nM. The detection results of Cr(VI) in actual environmental samples demonstrate that the Au NTPs colorimetric probe (Au-N-Probe) is expected to be applied to the detection of Cr(VI) in water environmental samples such as lake water and industrial wastewater.
Thiophene modified organosilanes were synthesized by two manageable steps. Firstly, thiophene based Schiffbases (3a-3c) were synthesized by the simple condensation reaction further triazole allied organosilanes (4a-4c) were incorporated via Click chemistry and then characterized by various spectral techniques. The sensing property of synthesized compound 4a was studied using absorption studies. Among various metal ions compound 4a showed the recognisable behaviour towards trivalent form of chromium ion. The limit of detection and association constant were estimated to be 0.34 x 10⁻⁷M and 4.4 x 10⁵ M⁻¹respectively.The selectivity of sensor 4a was unaltered in the presence of other metal ions. Job’s variation method was opted for calculating binding stoichiometry which showed 1:1 binding ratio. Binding mechanism was clarified by ¹HNMR spectroscopy. Further compound 4a and complex 4a-Cr³⁺ were explored using density functional theory. Molecular docking study was carried out with HIV-1 RT and it showed the inhibitory activity towards reverse transcriptase by blocking the active site of enzyme. The lowest binding energy was found to be -6.91kcal/mol indicating effective association between ligand and protein. Hence compound 4a may act as a good potent inhibitor against HIV-1 reverse transcriptase enzyme.
Luminescent coordination polymers (CPs) can be as promising sensors in which an analyte-induced multi-responsive system with classy recyclability is conducive to the detection of plentiful deadly contaminants. A ternary Cd(Ⅱ) CP, namely, [Cd(L)0.5(1,8-NDC)·H2O]n (1) (1,8-H2NDC = 1,8-naphthalenedicarboxylic acid) was constructed from the new flexibility 1,5-bis(thiabendazol-1-yl)pentane (L) and 1,8-H2NDC ligands under hydrothermal conditions. 1 possesses a 1D chain structure. 1 displays excellent pH resistance and luminescent sensing properties. 1 represents the first-ever CP for significant fluorescence “turn-on” detection of Al³⁺ and Cr³⁺ as well as ratiometric response to norfloxacin (NOR), even with the coexistence of other interferents. The luminescent sensing mechanism of 1 toward different analytes was discussed in detail.
Nanoflakes are materials with high dispersion, a large specific surface area, and a high number of active sites that can provide a good platform for various fluorescence sensors and are very popular among researchers. In this study, a nanoflake-like zinc metal-organic framework (Zn-MOF) was successfully synthesized from the organic ligand 1,2,4,5-tetra(1H-imidazol-1-yl)benzene and zinc nitrate. The synthesized Zn-MOF nanoflakes are extremely soluble in water and exhibit high fluorescence stability. Since Cr2O72- can significantly quench the fluorescence of Zn-MOF aqueous solution, a rapid detection method for Cr2O72- content in water was constructed with a linear range and linear correlation of 0.3-20 μM and 0.992, respectively. The fluorescence quenching constant of the Zn-MOF is KSV = 2.003 × 104 M-1, and the detection limit for Cr2O72- is as low as 0.09 μM. Through the study of fluorescence lifetime and UV absorption, it is proven that the mechanism of Cr2O72- quenching the fluorescence of the Zn-MOF is the inner filter effect. In addition, even after being applied five times, the Zn-MOF still maintained good detection performance for Cr2O72-. The proposed method was successfully applied to the determination of real water samples, confirming that it can be used as an alternative method for the detection of Cr2O72- in environmental samples.
Highly sensitive and selective fluorescence sensing of antibiotics and heavy metal ions are extremely vital to safeguard human health. Two new water-stable ternary coordination polymers (CPs), {[Cd(NPTA)(L)]·1.75H2O}n (1) and [Co1.5(BTC)(L)]n (2) (H2NPTA = 3-nitrophthalic acid, H3BTC = 1,3,5-benzenetricarboxylic acid, and L = 1,5-bis(benzimidazole-2-yl)pentane) were prepared through the hydrothermal process. 1 features a 1D zigzag infinite chain which is linked into a 2D network via π−π stacking interactions, while 2 shows a 2D 3,4L35 layer and can be further extended into a 3D supramolecular framework by hydrogen-bonding interactions. The two CPs display superior thermal and chemical stability in a wide pH range from 3 to 12. Furthermore, both 1 and 2 can be as the dual-responsive probes for selective sensing of enrofloxacin (ENR) and Al³⁺ ions with reusability.
Background
Copper is one of several heavy metals. A low concentration of copper is vital for animals and plants, whereas it is highly toxic to aquatic plants and bacteria in a high concentration. Therefore, copper ions in water and food must be controlled, and as a result, the development of novel methods for the determination of copper in water samples is of interest.
Objective
Different techniques have been proposed for copper ions extraction and determination. The magnetic solid -phase extraction method is considered superior to the other method for simplicity, its higher enrichment, and the need for lower quantities of solvents. The novel modified magnetite nanoparticles as the sorbent, along with the atomic absorption spectrometry analysis, can be a low‐cost, simple and rapid method for this propose.
Methods
Traces of Cu(II) in environmental samples were preconcentrated using a novel magnetic adsorbent developed based on 2,2´-((1E,1´E)-hydrazine-1,2-diylidenebis(methanylylidene)) diphenol coated magnetite nanoparticles. The influence of ligand concentration, amount of adsorbent, pH, type of eluent, sample volume, and effects of interfering ions was optimized. The adsorbed species were eluted for analysis through atomic absorption spectrometry.
Results
A linear calibration curve was recorded from 2 to 40 µg ml-1 (r2= 0.999) under optimal conditions, and the detection limit of the method was as low as 1.6 µg ml-1. Also, good recoveries were obtained for the real sample analysis.
Conclusion
The developed procedure constituted a rapid extraction, a low-cost and efficient method, and was used for the analysis of copper ions in the tap, river, and lake water.
A novel Co-based metal organic framework (Co-MOF) was applied as an electroactive material in carbon paste electrode for determination of Cr(III) ion with high selectivity and sensitivity. This Co-MOF was established by transforming the monoclinic structure of the Schiff base as a linker into a 3-D Co-MOF tetragonal system using the cobalt ion as a node under a 1.5:1 molar ratio between the Schiff base and cobalt ion by using sonochemical synthesis under optimal conditions. Many characteristic tools were used to test the newly synthesized Co-MOF. The Co-MOF would have a nanometric, mesoporous character (average particle size 45-73 nm and pore diameter 5.0467 nm), 270.201 m²g⁻¹ surface area, and hydrophobicity (average contact angle =143.23o). Because of its large surface area, porous structure, and electrocatalytic behavior, metal organic framework is a fascinating material to use as an ionophore. This newly synthesized Co-MOF ionophore has been used to determine Cr(III) ions in a variety of samples with high accuracy and precision (RSD % = 0.75-2.55) and the data illustrated a concord with those acquired by atomic absorption spectroscopy (AAS). The proposed carbon paste electrode showed a Nernstian slope of 19.96±0.53mV decade⁻¹ with a detection limit of 4.3×10⁻⁹ mol L⁻¹, covering a linear range of 5.0×10⁻⁹ – 1.0×10⁻² mol L⁻¹ and fast response time of (<10s) with long-time stability of 2 months over pH range of 3.0 – 6.2. The proposed sensor was highly selective for Cr(III) ions, and the values of selectivity coefficients assessed using the fixed interference method (FIM) and the separate solution method (SSM) which were long recognized.
Water pollution has become one of the most worrisome environmental problems due to its harmful to human health and environmental safety. Thus, the design and development of robust and porous materials for detection and removal of pollutants from wastewater is extremely significant. Herein, a water-stable urea-containing 3D Cd-based metal-organic framework (MOF), {[Cd(L)0.5(bpe)0.5(H2O)]·x(solv)}n (MOF-1) (H4L = 5,5'-(((1,4-phenylenebis(azanediyl))bis(carbonyl))bis(azanediyl))diisophthalic acid) was prepared using urea-functionalized tetracarboxylate H4L ligand. The activated MOF-1 (MOF-1a) showed fast, sensitive, selective, and recyclable discrimination of nitrofurazone (NFZ) and nitrofurantoin (NFT) antibiotics, 2,4,6-trinitrophenol (TNP) explosive, as well as Cr2O7²⁻ by strong luminescence quenching and obvious red-shift of maximum emission. Unfortunately, MOF-1a has low adsorption capacity for the above pollutants owing to its small pore. To improve this disadvantage, MOF-1 crystals were in situ grown on the macroporous melamine foam (MF) by a facile one-pot solvothermal method, generating a MOF-1@MF composite with stability and high voids. The MOF-1@MF exhibited rapid, enhanced, and recyclable adsorption capacity toward NFZ, NFT, TNP, and Cr2O7²⁻ in water or even aqueous solutions with different pH values. Combination of the accessible functional sites in MOF-1 and macroporous structures of MF makes MOF-1@MF composite stand out as an excellent adsorbent in wastewater treatment. This work not only presents a water-stable MOF for selective recognition of NFZ, NFT, TNP, and Cr2O7²⁻, but also provides a facile one-pot strategy to prepare MOF-based composites for high-performance removal of above pollutants from water, promoting their practical application in water quality monitoring and wastewater purification.
Three coordination polymers (CPs), namely {[Co(L)(dpa)]·H2O}n (1), {[Zn(L)2(dpb)]}n (2) and {[Zn(L)(dpe)]}n (3), have been assembled through a dual-ligand strategy of a semi-rigid dicarboxylic acid (H2L = 1,4-bis(4-phenoxy)benzenedicarboxylic acid) with the help of different N-donor co-ligands (dpa = di(pyridin-4-yl)amine, dpb = 1,4-di(pyridin-4-yl)benzene), dpe = trans-1,2-di(4-pyridyl)ethylene). Single crystal X-ray diffraction analyses reveals that compound 1 is a 4-fold interpenetrating 2D sql network and compound 2 is a 2-fold interpenetrating 2D sql network, although the final structures are different because of various inter-layer stacking modes. Compound 3 is a 8-fold interpenetrating 3D dia framework containing an octahedral cage. A photoluminescence investigation shows that compounds 2 and 3 exhibit strong fluorescence originating from the intra-ligand charge transfer transitions. Benefiting from its chemical stability and luminescent properties, compound 2 possesses multi-functional fluorescent responses toward the Fe³⁺ ion, the Cr2O7²⁻ ion and the NZF antibiotic in aqueous medium. The KSV values of compound 2 are 4.68 × 10⁴ M⁻¹ for the Fe³⁺ ion, 7.23 × 10⁴ M⁻¹ for the Cr2O7²⁻ anion, and 1.03 × 10⁴ M⁻¹ for the NZF antibiotic. Additionally, the possible mechanism for the luminescence quenching has been investigated.
High sensitivity and selectivity for detection of metal ions are very important to protect human health. Fluorescent metal-organic framework (MOF) as a new sensing material has attracted more and more...
Heavy metal pollution is a serious environmental problem in some regions. Regular monitoring heavy metal contaminations in the environment is quite significant for human life and health. In this work, we utilize [email protected] nanoparticles (NPs) as the probe for sensitively detecting Cd²⁺ and Cr³⁺ in aqueous solution by dark-field optical microscopy (DFM) based single-particle detection (SPD) method. Herein, Cd²⁺ will cause the probe aggregation and exhibit an obvious red-shift of the localized surface-plasmon resonance (LSPR) peak. In the presence of Cr³⁺, noticeable increase in scattering intensity from the probe together with a weak red-shift of its LSPR peak is shown. Moreover, Cd²⁺ and Cr³⁺ can be quantified statistically through calculating the ratio of color change by DFM. Under optimal conditions, the linear dynamic ranges are obtained from 1 to 5 and 2 to 10 μM with detection limit of 11.5 and 26.8 nM for Cd²⁺ and Cr³⁺, respectively. Due to the ultra-high sensitivity and excellent specificity, this method is expected to have broad applications such as environmental monitoring and groundwater analysis in the future.
In this work, a multivariate metal-organic framework (MOF) (9-1-MOF-253-NH2) with mixed ligands is firstly constructed through solid solution approach under solvothermal conditions. Then, a Rhodamine B (RhB)-functionalized compound ([email protected]2) with bright red fluorescence is obtained by covalent post-synthetic modification (PSM). Due to possessing efficient and stable luminescent properties and robust framework, the sensing application of this material ([email protected]2) is explored. Remarkably, the water-tolerance and reusable [email protected]2 can specifically recognize and detect Cr2O7²⁻/CrO4²⁻ based on fluorescence quenching mechanism. Moreover, the sensor shows many excellent sensing performances for Cr2O7²⁻/CrO4²⁻ including high selectivity, good anti-jamming ability, great sensitivity (0.863 μM and 0.789 μM, respectively), and fast response speed. More importantly, the [email protected]2 can act as a fluorescent probe using for the detection of the Cr2O7²⁻/CrO4²⁻ content in milk and tap water samples with good accuracy and sensitivity. Furthermore, the possible sensing mechanisms of [email protected]2 towards Cr2O7²⁻/CrO4²⁻ are investigated in detail.
A novel luminescent Zn(II)-based metal–organic framework with twofold interpenetrating [Zn(DHT)(BPP)]n (GUPT-2) {GUPT = Guangdong University of Petrochemical Technology, H2DHT = 2,5- dihydroxyterephthalic acid, and BPP = 1,3-di(4-pyridyl)propane} was successfully synthesized...
Two families of lanthanide metal-organic frameworks (Ln-MOFs), namely {[Ln2L2(DMF)4]·xDMF·yH2O}n(Ln = Ce(1), Pr(2), Sm(3), Eu(4), Gd(5);x= 0, 1;y= 0, 1) and {[Ln2L2(H2O)2.5]}n(Ln = Dy(6), Ho(7)), have been solvothermally synthesized based on the semi-rigid tripodal ligand 5-(4-carboxybenzyloxy)isophthalic acid (H3L). Utilizing the excellent luminescence property and water stability, Eu(4) exhibited efficient luminescence responses toward Fe³⁺, Cr2O7²⁻, and NFT/NZF antibiotics in aqueous medium with high sensitivity and selectivity. The detection limits (LODs) are 3.69 μM for Fe³⁺ion, 4.01 μM for Cr2O7²⁻anion and 9.92 μM/11.4 μM for NFT/NZF antibiotics, suggesting that Eu(4) is a good and simple multifunctional luminescent sensor. Additionally, the Gd(iii) ions exhibit a weak antiferromagnetic interaction in the dinuclear SBUs of Gd(5), and Dy(6) shows slow magnetic relaxation behaviors under zero dc field.
MAPbBr3 has a great prospect in various fields, due to excellent fluorescence quantum efficiency, band gap tunable and short of fluorescence lifetime. However, the instability of MAPbBr3 seriously impedes its application. Herein, the MAPbBr3 embedded in Zinc-Cobalt binary zeolitic imidazolate framework (ZIF-8Cox%, x=0-20) has been developed to fabricate [email protected]% for detecting Fe3+ in mixing various metal ions water. The investigation of concentration of doping Co2+ on the emission intensities of [email protected]% composite demonstrated that the concentration of 5% with Co2+ showed superior fluorescence intensity after 30 days in the water. The fluorescent sensing studies indicated that [email protected]% can detect Fe3+ ion in water with high sensitivity and selectivity even in the presence of other interfering metal ions including Fe2+ ion. Moreover, the potential fluorescence sensing mechanism of [email protected]% for Fe3+ ion in aqueous solution was also discussed.
In this work, novel carbon dots codoped with nitrogen and sulfur (NSCDs) were used as fluorescent probes to detect Cr3+. These NSCDs exhibited strong fluorescence, which could be rapidly quenched by Cr3+. The fluorescence intensity of the NSCDs solutions would decrease linearly with increasing Cr3+ concentration (0–40 μM). After calculation, the detection limit was 7.8 nM, indicating the NSCD probes have the excellent sensitivity. Then, it was determined that the NSCD probes were quenched only by Cr3+, even in the presence of other ions, thereby showing the NSCD probes possess the excellent anti-interference and selectivity ability. The mechanism of the quenching of the fluorescence of NSCDs by Cr3+ ions may be related to the enhanced non-radiation emission attributed to the destroyed NSCD surface. Due to their nontoxicity and biocompatibility, these NSCDs could be applied in detecte Cr3+ in living cells.
We herein report a new lanthanide metal-organic framework (MOF) that exhibits excellent chemical stability, especially in the aqueous solution over a wide pH range from 1 to 14. In contrast to many reported lanthanide MOFs, this Tb-based MOF emits cyan fluorescence inherited from the integrated AIE-active ligand, rather than Ln³⁺ ions. More remarkably, its fluorescence signal features a highly selective and sensitive “turn-off” response toward CrO4²⁻, Cr2O7²⁻ and Fe³⁺ ions, highlighted with the low detection limits down to 68.18, 69.85 and 138.8 ppm, respectively. Thus, the exceptional structural stability and sensing performance render this material able to be a superior luminescent sensor for heavy metal ions in wastewater.
Hexavalent chromium ion (Cr⁶⁺) is highly toxic to human health and environment. Herein, high-performance detection of Cr⁶⁺ is of great import. In this study, a rapid and sensitive multicolor colorimetric method for detection of Cr⁶⁺ in aqueous solution was established on the basis of Cr⁶⁺ etching of gold nano-double [email protected] nanorods (Au [email protected] NRs). Au [email protected] NRs was synthesized by a modified seed-mediated growth method. The catalytic etching induced by Cr⁶⁺ changed the morphology of Au [email protected] NRs, leading to the attenuation of surface plasma resonance (SPR) and the redshift of absorption spectra. Meanwhile, Au [email protected] NRs exhibits obvious color changes from orange to pink, to purple, and finally becomes colorless with the increasing concentrations of Cr⁶⁺. With such a design, naked-eye detection of Cr⁶⁺ was realized with high sensitivity. The proposed multicolor sensing method showed a good linearity between the redshift change of absorption peak (△λ) and the concentrations of Cr⁶⁺ in the range from 2.5 to 40 μM. The limit of detection (LOD) was calculated as 1.69 μM in aqueous solution. In addition, successful detection of Cr⁶⁺ in tap water and Yangtze River water, indicating the real applications of Au [email protected] NRs probe in monitoring Cr⁶⁺ in environment.
Regarding the Cr(III) importance in the industrial, environmental, and even biological systems, development of highly selective and sensitive Cr(III) sensor is a challenge. In this work, a new carbon paste electrochemical sensor containing a synthesized bis(aminotriazoles) derivative namely 1,3-bis[4-amino-5-benzyl-1,2,4-triazol-3-ylsulfanyl]propane (BABTSP) as the Cr(III) selective ionophore was described. Factors affecting sensor’s response were studied and optimized. The proposed sensor exhibited a Nernstian slope of 20.05 ± 0.35 mV decade⁻¹ covering broad linear range of 1.0 × 10⁻⁸−5.0 × 10⁻² mol L⁻¹ and detection limit was 8.0 × 10⁻⁹ mol L⁻¹ for 3 months over pH range of (2.3–5.2) and fast response time (<10 s). The proposed sensor was selective for Cr(III) ions that was confirmed by separate solution method (SSM) and fixed interference method (FIM) . The sensor was precise and reproducible (RSD% range = 0.8–2.45) and effectively used in potentiometric titration of Cr(III) against EDTA and in diverse water samples analysis with recovery data of 96.08–100.2%. The lipophilicity of the applied ionophore was investigated through contact angle measurement technique and average contact angle was 127.59° that resulted in sensor’s mechanical stability. To study the response mechanism and morphology of the prepared sensor, scanning electron microscope (SEM), energy dispersive X-ray (EDX) and FT-IR spectroscopy were used.
This paper outlines a method for the analysis of the oxidation states of Cr employing a suitable chelating agent and the cloud point phenomenon for Cr(III) and total Cr analysis. The method involves preconcentration of metal chelates followed by flame atomic absorption spectrometric analysis. We use Schiffs base(N,Ń-bis-(α-methyl salicylidene) propane-1,3-diimine) as a chelating agent for cloud point extraction for the first time. Cr(III) reacts with chelating agent for the formation of a Hydrophobic complex, which is subsequently entrapped in the surfactant micelles. The Cr(VI) assay is based on its reduction to Cr(III) by the addition of concentrated H2SO 4 and ethanol to the sample solution; Cr(III) subsequently reacts with chelating agent in a similar manner. The condensed surfactant phase with the metal chelate is introduced into a flame atomic absorption spectrometer, whereby discrimination of Cr species is feasible by calculating the Cr(VI) concentration from the difference between total Cr and Cr(III). After optimization of the complexation and extraction conditions, a good enrichment factor was obtained. The analytical curves were rectilinear up to 75 μgL -1 and the relative standard deviations were 2.3% for both species. The limits of detection are sufficiently low and lie around 0.1 μgL -1. The proposed method was applied successfully to the determination of Cr(III) and Cr(VI) in tap water and river water samples. The method was validated by the analysis of certified reference material BCR 544 for both species.
The concept of cloud point phenomenon is used to perform metal speciation after the studied metallic forms have reacted with suitable ligands for the formation of hydrophobic complexes, which are subsequently entrapped in the surfactant micelles. As an analytical demonstration, trace concentrations of Cr(III) and Cr(VI) were conveniently detected in samples with a complex matrix, such as sea water, without any laborious and expensive treatment using flame atomic absorption spectrometry. The speciation of Cr is performed using Triton X-114 as surfactant and, as chelating agents, ammonium pyrrolidinedithiocarbamate for Cr(VI) and 8-hydroxyquinoline for Cr(III). Analytical curves were rectilinear up to concentrations of 130 µg l−1 for Cr(III) and 85 µg l−1 for Cr(VI) with detection limits of 1.4 µg l−1 and 0.65 µg l−1, respectively. The method affords recoveries in the range 96–104% and a relative standard deviation lower than 2.2%. It is proved that the method can be successfully employed as an alternative to the commonly used preconcentration and speciation analytical techniques. By selecting the appropriate complexing agent(s) other metal speciations are feasible provided that some detailed study precedes the application.
Cloud point extraction is a separation and preconcentration procedure that has been extensively applied for trace metal determination in several different matrices. Its major advantages are simple experimental procedures, low cost, high preconcentration factors, and environmental safety. These aspects include it in a set of analytical methods in agreement with the “green chemistry” principles. The surfactants characteristics and the process of micelle formation are outlined for a better understanding of the technique. After general considerations about the cloud point extraction basis and its extraction mechanism for metal chelates are considered, selected spectroanalytical techniques and their application for analysis of the micellar phase are discussed. The micellar extraction in metal speciation analysis, the on‐line incorporation of cloud point extraction to flow injection analysis, and coupling with capillary electrophoresis are described.
The toxicity of chromium in the environment is dependent on the species in which it exists. This paper outlines a method for the analysis of the oxidation states of Cr employing a suitable chelating agent and the cloud point phenomenon for Cr(VI) and total Cr analysis. The method involves preconcentration of metal chelates followed by air-acetylene flame atomic absorption spectrometric analysis. The chelating agent chosen for this task is the ammonium pyrrolidinedithiocarbamate, which reacts with either Cr(VI) or total Cr under specific experimental conditions. The condensed surfactant phase with the metal chelate(s) is introduced into a flame atomic absorption spectrometer, whereby discrimination of Cr species is feasible by calculating the Cr(III) concentration from the difference between total Cr and Cr(VI). A multivariate design was employed to study the variables affecting the overall analytical performance for total Cr assay. The analytical curves are rectilinear up to 100 micrograms l-1 for both oxidation states of the metal. The limits of detection are 0.6 microgram l-1 and the relative standard deviation (n = 5) at a concentration of 30 micrograms l-1 for both species is around 2.0%. The method was validated by analysing BCR 544 reference material certified for both Cr species. High recoveries in the range 96-107% were attained for the environmental and biological samples tested.
A rapid, sensitive and accurate atomic absorption method for Cr(III) and Cr(VI) ions was developed based on the cloud-point extraction (CPE) technique. Cr(III) reacts with a new Schiff's base ligand to form the hydrophobic complex, which is subsequently entrapped in the surfactant micelles. The Cr(VI) assay is based on its reduction to Cr(III) by the addition of concentrated H2SO4 and ethanol to the sample solution. The condensed surfactant phase containing the metal chelates is introduced into an atomic absorption spectrometer. The relative standard deviations were 2.1% for both species and the limits of detection were around 0.17 microg l(-1).
Due to its wide industrial use, chromium is considered a serious environmental pollutant. Contamination of soil and water by chromium (Cr) is of recent concern. Toxicity of Cr to plants depends on its valence state: Cr(VI) is highly toxic and mobile whereas Cr(III) is less toxic. Since plants lack a specific transport system for Cr, it is taken up by carriers of essential ions such as sulfate or iron. Toxic effects of Cr on plant growth and development include alterations in the germination process as well as in the growth of roots, stems and leaves, which may affect total dry matter production and yield. Cr also causes deleterious effects on plant physiological processes such as photosynthesis, water relations and mineral nutrition. Metabolic alterations by Cr exposure have also been described in plants either by a direct effect on enzymes or other metabolites or by its ability to generate reactive oxygen species which may cause oxidative stress. The potential of plants with the capacity to accumulate or to stabilize Cr compounds for bioremediation of Cr contamination has gained interest in recent years.
A sensitive and selective method has been developed for the speciation of Cr(III) and Cr(VI) in natural water using a nanometer titanium dioxide micro-column (20 mm×3.0 mm i.d.) and inductively coupled plasma atomic emission spectrometry (ICP-AES). Under the optimized conditions (pH 6.0, flow rate 1.0 ml min−1), Cr(III) was retained on the column, then eluted with 2.0 mol l−1 HCl and determined by ICP-AES. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by ascorbic acid as reducing reagent. The adsorption capacity of nanometer TiO2 for Cr(III) was found to be 7.6 mg g−1. The detection limit for Cr(III) was 0.32 μg l−1 and the relative standard deviation (R.S.D.) was 2.4% (n=11, C=100 μg l−1) with an enrichment factor of 50. The proposed method has been applied to the determination and speciation of chromium in natural water samples with satisfactory results.
A new method based on cloud point extraction (CPE) separation and electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV‐ICP‐OES) detection was proposed for the determination of chromium species. Thenoyltrifluoracetone (TTA) was used as both an extractant for CPE of Cr(III) and a chemical modifier for ETV‐ICP‐OES determination. When the system temperature is 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 is based on substracting of Cr(III) from total chromium. The main factors affecting cloud point extraction and the vaporization behavior of the analyte were investigated in detail. Under the optimized conditions, the limit of detection (LOD) for Cr(III) was 0.22 µg/L by preconcentration of a 10 mL sample solution, and the relative standard deviation (RSD) was 3.8% (CCr(III)=0.5 µg/mL, n=5). 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.
Chromium is introduced into the environment by effluents in several industries. It is important to control this element since it is both toxic and carcinogenic. As its toxicity depends on its state of oxidation, it is especially interesting to determine its most abundant species, Cr(III) and Cr(VI).In this overview, we describe the requirements for chromium determination and speciation and review the analytical methods that have been used in these studies. Focusing in particular on developments since 2000, we examine the features of detection techniques, pre-treatments and applications of the various methods.
In this article, the contents and distribution of total chromium, Cr(III) and Cr(VI) in various cigarettes and cigarette ashes were determined by using a cloud point extraction (CPE) separation/preconcentration combined with graphite furnace atomic absorption spectrometric (GFAAS) detection. Different extraction reagents, such as tetramethylammonium hydroxide (TMAH), Na2HPO4, Na2CO3/NaOH, NaOH and H2O, were tested for the extraction of Cr species, and the extraction efficiency was estimated. The experimental results showed that TMAH was the most efficient extraction reagent for the analyte in cigarette samples. By using the established method, the total chromium, Cr(III) and Cr(VI) in various cigarettes and cigarette ashes were determined and their distribution was studied. It was found that Cr(III) is a main species in cigarettes, but that it can be partly oxidized to Cr(VI) during smoking.
We describe a case of pyogenic spondylitis/spondylodiscitis (PS) after stellate ganglion block (SGB). The clinical pictures of 24 cases of post-SGB PS reported in the literature are reviewed. The most serious sequelae were spinal compression symptoms due to epidural spread of inflammation or crush of a vertebral body, meningitis, and dyspnea due to retropharyngeal abscess.
A Pb(PDC) 2 coprecipitation separation and preconcentration combined with slurry sampling fluorination assisted electrothermal atomic absorption spectrometry with PTFE as chemical modifier has been developed for the speciation of Cr III and Cr VI . Base on the variation of the pH, this method can soundly separate Cr III and Cr VI at pH 4.0 and 9.0, respectively. The experimental conditions of the coprecipitation and GFAAS determination were investigated systematically. Under the optimum conditions, the linear range of Cr III and Cr VI was from 0.5 to 80 ng/ml, and detection limit was 0.02 ng/ml with the RSD of 3.2% for Cr VI ( n = 9, C = 1 ng/ml) and 3.9% for Cr III ( n = 9, C = 1 ng/ml). The proposed method has been applied for the analysis of Cr III and Cr VI in natural water and tea infusion samples with satisfactory recoveries.
Aqueous solutions of certain surfactant micelles exhibit phase separation behavior upon temperature alteration. This phenomenon can be exploited in separation science for the development of extraction, purification, and preconcentration schemes for desired analytes. Since the addition of just a small amount of an appropriate nonionic or zwitterionic surfactant to the aqueous sample solution is required, this approach is convenient and fairly benign, eliminating the need for the use of organic solvents as in conventional liquid−liquid or solid−liquid extraction. The basic features, experimental protocols, and selected recent applications of this alternative extraction approach, termed cloud point extraction (CPE) or micelle-mediated extraction (ME), are briefly reviewed. In addition, the advantages, limitations, and anticipated future directions of this methodology are discussed.
This work proposes a new extraction method for chromium based on the two-phase aqueous system isopropyl alcohol-ammonium
sulfate-ammonium thiocyanate (i-PrOH-(NH4)2SO4-NH4SCN), and the related experimental conditions are optimized. The results show that chromium (III) can be quantitatively extracted
under the selected conditions: 4 mL of i-PrOH, 200 μL of 2 mol/L sulfuric acid, 1 mL of 4 mol/L NH4SCN and 3 mL of saturated (NH4)2SO4 solution (Vtotal=10 mL). Application of the proposed method to speciation analysis of plasma chromium was also investigated and satisfactory
results were obtained.
The purpose of this article is to review and evaluate cloud point extraction of metals and its coupling to different contemporary
instrumental methods of analysis. This review covers a selection of the literature published on this topic over the period
mainly between 1997 and September 2005 (consisting of 50 publications). The current state of the art for CPE concerning metals
and metal chelates is presented with special emphasis on the hyphenation of this interesting extraction/preconcentration approach
mediated by surfactants to spectrophotometry, atomic spectroscopy and separation techniques. We present contemporary CPE developments
concerning metal speciation and determination and their application to different environmental, clinical, geological and food
samples. Strategies for method development as well as future perspectives are also covered.
A new method based on the cloud point extraction (CPE) technique was applied for the differentiation and the selective determination of Cr species. Cr(III) reacts with 8-hydroxyquinoline (8-HQ) in a surfactant solution yielding a hydrophobic complex, which then is entrapped ‘in situ’ in the surfactant micelles. The Cr(VI) assay is based on its reduction to Cr(III) by sulfite which subsequently reacts with 8-HQ in a similar manner. In order to increase the sample throughput a flow injection analysis (FIA) system allied to fluorimetric detection was employed. Using a simple FIA configuration the greatest sensitivity was obtained which under the optimum working conditions, allows the reliable determination of Cr(III) and/or Cr(VI) at levels as low as 0.2 μg l−1, in various samples even in those with complex matrix (sea water, pharmaceuticals). The whole procedure is straightforward, without any laborious, expensive and hazardous treatment and was proved to tolerate interferences among the cations and anions tested. Moreover, the analytical approach offers distinct advantages over the commonly used analytical methods especially for large number of samples with complex matrixes, which would unavoidably require arduous and delicate pretreatment.
The changes in physical properties of sample solutions aspirated in atomic spectrometry through the addition of surfactants improve nebulization efficiency, enhance wettability of solid surfaces used for atomization, improve compatibility between aqueous and organic phases, and can achieve good dispersion of small particles in 'slurry' techniques. The ability of the organized media to enhance detection of atomic spectroscopic methods by favorable manipulation of physical and chemical properties of the sample solution is discussed, along with the extension of separation mechanisms by resorting to organized media, and the synergistic combinations of liquid chromatography separations and atomic detectors using vesicular mobile phases.
The extraction technique based on phase separation in aqueous micellar solutions is reviewed. The technique has now been utilized for separation and preconcentration of metal chelates, organic compounds, and proteins. Additionally, the phase behavior of the micellar solutions and recent advances in the phase separation technique are also described. In the extraction of metal chelates, distribution equilibria are considered. In contrast to conventional solvent extraction, the distribution of metal chelates into a condensed surfactant phase (surfactant-rich phase) was dependent on metal ions. Proteins were extractable into the surfactant-rich phase according to their hydrophobicity. The recent use of affinity ligands and water-soluble polymers for controlling extractability of proteins are also introduced.
We present contemporary developments in the field of surfactants and micellar systems together with their applications in analysis, with the aim of highlighting some of the most important aspects of this area of research. We pay particular attention to speciation through cloud-point extraction (CPE), as well as to the differentiation of metallic species, oxidation states and complexes prior to their determination. We also present a theoretical background and a guide for experimentally optimizing CPE. We conclude by discussing some problems arising from the use of surfactant systems, while proposing future trends and potential new areas for their application.
Ion chromatography and laser-enhanced ionization were combined for the speciation of chromium at the trace level. Several one- and two-step excitation schemes were examined, in the UV and visible regions of the spectrum. It was found that a near-resonant two-step/one-color excitation scheme, using a single strongly saturating laser for the simultaneous excitation of both steps of the (3d54s) 7S3→(3d54p) 7P30→(3d44s5s) 7D4 sequence, provides the best analytical results. This scheme was applied to the determination of total chromium in solutions directly aspirated into the air–acetylene flame, and to the determination of Cr(III) and Cr(VI) separated by ion chromatography. A detection limit of 0.5 ng/mL was obtained by direct solution aspiration, with a dynamic range covering four orders of magnitude. Detection limits of 5 ng/mL for Cr(III) and 4 ng/mL for Cr(VI) were obtained by ion chromatography and laser-enhanced ionization.
Micelle-based techniques can be utilised for the preconcentration and separation of metal ions, which are either in their native form or in chelates that are produced after reaction under appropriate conditions. In this review, the metal analysis is based on an a priori phase separation in aqueous micellar solutions. In principle, the micelle-mediated extraction technique involves cloud-point extraction, but this review also deals with micellar-enhanced ultrafiltration and reversed micellar phase extraction. The different aspects of surfactant-enhanced, non-classical, metal-extraction schemes are presented and the interactions with the micellar entity are given. The fundamentals of micellar solutions and their solubilization capabilities are highlighted. Also outlined are practical problems when this sort of extraction is implemented in conjunction with different analytical detection systems.
The growing awareness of the strong dependence of the toxicity of heavy metals upon their chemical forms has led to an increasing interest in the qualitative and quantitative determination of specific metal species. Speciation has therefore become an important topic of present-day analytical research. This article describes the main types and areas of application of speciation analysis, and the use of sequential extraction in speciation studies. Brief characteristics of the basic types of speciation analysis, examples of their applications, and the usage of the various analytical techniques are also included.
Diperoxo chromium oxide is produced by reaction of hydrogen peroxide on chromium(VI). Diperoxo chromium creates a complex with ethyl acetate, while chromium(III) remains in an unchanged form in the aqueous phase. By this means chromium(VI) can be extracted into ethyl acetate from the aqueous phase. The optimal conditions of Cr(III)–Cr(VI) separation, as well as the chromium content of the ethyl acetate phase were determined with graphite furnace atomic absorption spectrometry. In the second extraction of Cr(VI) from ethyl acetate back into water phase an additional preconcentration of chromium(VI) can be carried out. The detection limit (3σ) of the developed method found to be 200 ng dm− 3 for the first extraction and 50 ng dm− 3 after using the twofold extraction. In consequence of the matrix free ethyl acetate phase after the first extraction, with this separation a really extensive preconcentration of chromium(VI) can be realized.
A procedure for chromium speciation by F AAS using a flow system has been proposed. In this system, Cr(III) and Cr(VI) ions were adsorbed sequentially onto a mini-column packed with silica gel modified with zirconium phosphate and a mini-column packed with silica gel modified with zirconium oxide, respectively. The elution of Cr(III) and Cr(VI) was made with, respectively, nitric acid solution and tris(hydroxymethyl)methylamine (THAM) solution in reverse mode and determination by flame atomic absorption spectrometry without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for Cr(III) and Cr(VI) was 20.8 and 24.9, respectively, using a preconcentration time of 3.75min. The limit of detection for Cr(III) and Cr(VI) was 1.9, and 2.3mugl(-1), respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 100mugl(-1) of chromium species, by analyzing a series of seven replicates, was lower than 3.0%. The accuracy was assessed through recovery experiments of water samples and using another methodology.
A rapid, sensitive and selective method is described for the determination of chromium(VI) in presence of 100-fold amounts of chromium(III) by flame atomic absorption spectrometry (FAAS) in conjunction with coprecipitative preconcentration of its ethyl xanthate complex onto naphthalene. The solid mixture consisting of the chromium(VI) complex together with naphthalene is dissolved in 8.0ml of dimethyl formamide (DMF) and chromium(VI) content was established by FAAS. Calibration graphs were rectilinear over the chromium(VI) concentration in the range 0-200mugl(-1). Five replicate determinations of 20mug of chromium(VI) present in 1.0l of sample solution gave a relative standard deviation of 3.1%. The detection limit corresponding to three times the standard deviation of the blank was found to be 0.5mugl(-1). The developed procedure has been successfully utilized for the estimation of chromium(VI), chromium(total) (after oxidation with bromate) and chromium(III) (by subtracting chromium(VI) content from chromium(total) value contents of several tannery industries.
Speciation (determination of the different physico-chemical species formed by an element) in a water sample is necessary for an understanding of the toxicity, bioavailability, bioaccumulation and transport of a particular element. The importance of speciation measurements and the various factors leading to changes in speciation are discussed in this review. Speciation in natural waters is a difficult task, and the analytical methods available and the results obtained are critically assessed.
Ore deposits containing chromium are heavily exploited for use in a variety of industrial processes. South Africa, the USSR, the Philippines, and Zimbabwe are the main producers of chromite ore (Ellis 1986). Annual world production of chromite is approximately 7 × 106 tons, roughly three orders of magnitude greater than natural rates of environmental mobilization (Eisler 1986). The largest users of Cr are the metallurgical and chemical industries (Langard and Norseth 1979). Most Cr for metallurgical purposes is used in stainless steel production and electroplating, whereas the chemical industry produces Cr compounds for incorporation into a diverse array of products including paint pigments, catalysts, wood preservatives, and tanning agents.
We sought to determine whether sympathetic blockade or infusion of prostaglandin E1 (PGE1) is better for vasodilation. We measured brachial artery blood flow (BABF) in 10 mongrel dogs using an ultrasonic time flowmeter to compare the effects of stellate ganglion block (SGB) and intravascular infusion of PGE1. The experimental protocol was designed as follows: 1) intravenous (IV) infusion of PGE1 at a rate of 10 ng x kg(-1) x min(-1) for 10 min, 2) IV infusion of PGE1 at a rate of 150 ng x kg(-1) x min(-1) for 10 min, 3) intraarterial infusion of PGE1 at a rate of 0.1 ng x kg(-1) x min(-1) for 10 min, 4) SGB with 0.5% mepivacaine 1.0 mL was used as a sympathetic blockade. These procedures were successively performed on each dog. Mean arterial pressure (MAP), heart rate (HR), and BABF were measured before and after each procedure for 40 min. MAP and HR did not change significantly after the procedures. BABF increased significantly after IV infusion of PGE1 150 ng x kg(-1) x min(-1), intraarterial infusion of PGE1 and SGB, reaching maximums of 157%, 174%, and 171% 10 min after IV infusion of PGE1 150 ng x kg(-1) x min(-1), intraarterial infusion of PGE1 and SGB compared with the prevalues, respectively. These data indicate that sympathetic blockade may produce the same vasodilation as IV infusion of PGE1 150 ng x kg(-1) x min(-1) and intraarterial infusion of PGE1 0.1 ng x kg(-1) x min(-1). Intravascular infusion of PGE1 could provide clinically equivalent vasodilation without the complications associated with SGB.
The aim of this study is to examine the duration and magnitude of vasodilative effect induced by sympathetic block with the addition of clonidine to mepivacaine.
We measured mean arterial pressure (MAP), heart rate (HR), and right and left brachial artery blood flow (BABF) before and after stellate ganglion block (SGB) in dogs. The experimental protocol was designed as follows: (1) left SGB using 1.0 mL 0.5% mepivacaine (n = 6) and (2) left SGB using the addition of clonidine 0.5 microg to 1.0 mL 0.5% mepivacaine (n = 6).
MAP and HR did not change significantly throughout the study in either group. Left SGB with mepivacaine increased left BABF significantly from 10 minutes through 50 minutes after SGB (baseline, 100%; peak at 10 minutes after SGB, 176% +/- 28%; P <.01). Left SGB with the addition of clonidine to mepivacaine induced a significant increase of left BABF from 10 minutes through 70 minutes after SGB (baseline, 100%; peak at 10 minutes after SGB, 223% +/- 42%; P <.01). The values of left BABF after SGB with the addition of clonidine to mepivacaine were significantly higher than those of SGB with mepivacaine alone from 10 minutes through 80 minutes after SGB (P <.05). Right BABF decreased significantly after SGB throughout the study in both groups.
The addition of clonidine increases both duration and magnitude of the vasodilative effect induced by sympathetic block over that caused by mepivacaine alone.
This article includes a survey of chromium (Cr) occurrence in different environmental compartments, its pathways in the environment and the cross-sectional presentation of Cr speciation methods against the background of Cr chemistry. The aim of the article is to demonstrate that knowledge of interconversion processes between different Cr forms is necessary to understand its behaviour and role in the environment, in addition to enabling reliable Cr speciation analysis to be performed. The current methods of Cr speciation are presented, characterized and their usefulness discussed. These must rely on superior separation and detection capabilities since Cr in environmental compartments is mostly at trace or ultra-trace level. The need for using unique techniques of sampling, storage, handling and separation for Cr speciation is documented.
Cloud point extraction (CPE) was applied as a preconcentration step for HPLC speciation of chromium in aqueous solutions. Simultaneous preconcentration of Cr(III) and Cr(VI) in aqueous solutions was achieved by CPE with diethyldithiocarbamate (DDTC) as the chelating agent and Triton X-114 as the extractant. Baseline separation of the DDTC chelates of Cr(III) and Cr(VI) was realized on a RP-C18 column with the use of a mixture of methanol-water-acetonitrile (65:21:14, v/v) buffered with 0.05 M NaAc-HAc solution (pH 3.6) as the mobile phase at a flow rate of 1.0 ml min(-1). The precision (R.S.D.) for eight replicate injections of a mixture of 100 microg l(-1) of Cr(III) and Cr(VI) were 0.6 and 0.5% for the retention time, 4.1 and 4.6% for the peak area measurement, respectively. The concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for HPLC separation and in the initial solution, was 65 for Cr(III) and 19 for Cr(VI). The linear concentration range was from 50 to 1000 microg l(-1) for Cr(III) and 50-2000 microg l(-1) for Cr(VI). The detection limits of Cr(III) and Cr(VI) were 3.4 and 5.2 microg l(-1), respectively. The developed method was applied to the speciation of Cr(III) and Cr(VI) in snow water, river water, seawater and wastewater samples.
Intracellular reduction of Cr(VI) results in the extensive formation of Cr-DNA adducts, among which Cr(III)-mediated DNA cross-links of glutathione, cysteine, histidine, and ascorbate represent a major class of DNA modifications. Cysteine-Cr(III)-DNA and glutathione-Cr(III)-DNA cross-links are the two most abundant lesions that collectively account for about 80% of all ternary Cr-DNA adducts in cultured cells. In vitro reduction of Cr(VI) also generates binary Cr(III)-DNA adducts, but their significant production in cells is uncertain. All ternary and a major fraction of binary Cr(III)-DNA adducts are formed by attack of DNA by Cr(III) complexes. The formation mechanisms for the relatively rare DNA-protein and interstrand DNA crosslinks have not yet been determined. All ternary Cr-DNA adducts were mutagenic during replication in human cells. The mutagenic and genotoxic potentials of Cr-DNA adducts were related to the bulkiness of the attached ligand, with large glutathione- and ascorbate-Cr(III)-DNA cross-links generating the highest yields of mutants. Cr-DNA adducts were responsible for all mutagenic and replication-blocking damage generated during reduction of Cr(VI) with cysteine or ascorbate, which are two main reducers of Cr(VI) in vivo. Nucleotide excision repair has been identified as the principal mechanism for removal of Cr-DNA adducts in human cells. The strong genotoxic potential of all main adducts and hypersensitivity of nucleotide excision repair deficient human cells to apoptosis and clonogenic death indicate that Cr-DNA adducts are also a significant cause of Cr(VI) toxicity. Thus, it appears that Cr-DNA adducts are key genetic lesions contributing to the induction of the main biological effects of Cr(VI), such as mutagenesis, replication inhibition, and cell death (Figure 6). The formation of genotoxic ternary Cr-DNA adducts is predicted to be independent of the reducing capacity of the cell and should exhibit linear dose dependence with respect to intracellular Cr(VI).
A new method based on the cloud point extraction (CPE) separation and electrothermal atomic absorption spectrometry (ETAAS) detection was proposed for the determination of chromium species. When the system temperature is higher than the cloud point extraction temperature (CPT) of selected surfactant p-octyl polyethyleneglycolphenyether (Triton X-100), the complex of Cr(VI) with dibromophenylfluorone (Br-PF) could enter surfactant-rich phase, whereas the Cr(III) remained in aqueous phase. Thus, an in situ separation of Cr(VI) and Cr(III) could be realized. Cr(VI) in surfactant-rich phase was analyzed by ETAAS and Cr(III) was calculated by subtracting of Cr(VI) from the total chromium which was directly determined by ETAAS. The main factors affecting the cloud point extraction, such as pH, concentration of Br-PF and Triton X-100, equilibration temperature and time, were investigated systematically. Under the optimized conditions, the quantitation limit for Cr(VI) as low as 0.01 microg/L was obtained by preconcentrating a 10 mL sample solution, and the relative standard deviation (n=6, c=2.0 microg/L) was 2.6%. The proposed method was applied to the speciation of chromium in different water samples and the recoveries in the range of 98.9-105.3% were obtained by spiking the real 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 the certified values.
Seroma, a collection of serous fluid, is the most common problem after breast surgery. The aim of this study was to review the effect of mechanical closure of dead space on seroma formation after breast surgery. There are two mechanical methods for closure of the dead space beneath skin flaps: compression by external pressure, and fixation of the flaps with sutures. There is no evidence to suggest that the routine use of a pressure garment or compression dressing is beneficial. However, it appears that suture flap fixation does reduce seroma formation, simplify postoperative care and dressing, and thus allow early removal of drains and discharge. Drains are helpful for mechanical closure of dead space, but in breast-conserving surgery this technique may preclude the use of a drain. However, previous studies have often been small in scale and poor in quality. Further studies should examine the effect of this technique on quality of life, cosmesis, and medical economics.
A speciation procedure for Cr(III) and Cr(VI) based on column solid phase extraction on Amberlite XAD-2010 and flame atomic absorption spectrometry combination. Cr(VI) was quantitatively recovered on Amberlite XAD-2010 resin at pH range of 2.0-3.0 as its diethyldithiocarbamate complex, while the recoveries of Cr(III) was below 5%. The influences of the various parameters including amounts of the reagents, eluent type and its volume, sample volume, etc., on the quantitative recoveries were examined. The interference of matrix and coexistent elements for method were studied. The detection limit (corresponding to three times the standard deviation of the blank) and the enrichment factor for Cr(VI) were found to be 1.28 microg/L and 25, respectively. To verify the accuracy of the method, drinking water certified reference material (CRM-TMDW-500) was analyzed and the results obtained were in good agreement with the certified value. The proposed method has been successfully applied to the speciation of Cr(III) and Cr(VI) in water samples and preconcentration of total chromium in environmental samples.
The synthesis of a new stable chelating resin from the polystyrene divinylbenzene copolymer is reported. The polystyrene is first functionalized with a phenolic group and then allowed to couple with diazotized anthranilic acid through the --N==N-- bond. The resulting polymer containing azophenolcarboxylate with an ONO chelating environment has been characterized by elemental analysis, hydrogen ion capacity, and water regain value. Its stability towards thermal and different chemical environments has been evaluated. The sorption capacity of the chelating resin for Cr(III) and Cr(VI) as a function of pH has been studied. The interesting point is that chromium(III) is selectively retained at ca. pH 5.0 and chromium(VI) at ca. pH 2.0. When packed in a column, the new material is able to separate Cr(III) from Cr(VI). Five replicate determinations of 10 microg Cr(III) and 10 microg Cr(VI) present in 100 mL solution gave recoveries of 96.9+/-2.9% (for Cr(III)) and 96.2+/-2.1% (for Cr(VI)) at the 95% confidence level. Calibration graph was linear over the concentration range of 0-250 microg L(-1) of chromium species with correlation coefficient (R) of 0.99994. The detection limits based on 3sigma criterion were determined to be 0.6 microg L(-1) for Cr(III) and 0.9 microg L(-1) for Cr(VI). The developed method was successfully used for the speciation of chromium in wastewater.
Micelle-mediated separation and cloud-point extraction Micelle-mediated extraction as a tool for separation and preconcentration in metal analysis
- E K Paleologos
- D L Giokas
Paleologos E K, Giokas D L, Karayannis M I (2005) Micelle-mediated separation and cloud-point extraction. Trends Anal Chem 24: 426 21. Stalikas C D (2002) Micelle-mediated extraction as a tool for separation and preconcentration in metal analysis. Trends Anal Chem 21: 343
The speciation of trace elements in waters. Talanta 29: 345 Determination of Cr(III) and total chromium in water samples
- Florence
Florence T M (1982) The speciation of trace elements in waters. Talanta 29: 345 Determination of Cr(III) and total chromium in water samples