Determination of ultra trace arsenic species in water samples by hydride generation atomic absorption spectrometry after cloud point extraction

Cloud point extraction (CPE) methodology has successfully been employed for the preconcentration of ultra-trace arsenic species in aqueous samples prior to hydride generation atomic absorption spectrometry (HGAAS). As(III) has formed an ion-pairing complex with Pyronine B in presence of sodium dodecyl sulfate (SDS) at pH 10.0 and extracted into the non-ionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-114). After phase separation, the surfactant-rich phase was diluted with 2 mL of 1 M HCl and 0.5 mL of 3.0% (w/v) Antifoam A. Under the optimized conditions, a preconcentration factor of 60 and a detection limit of 0.008 μg L⁻¹ with a correlation coefficient of 0.9918 was obtained with a calibration curve in the range of 0.03–4.00 μg L⁻¹. The proposed preconcentration procedure was successfully applied to the determination of As(III) ions in certified standard water samples (TMDA-53.3 and NIST 1643e, a low level fortified standard for trace elements) and some real samples including natural drinking water and tap water samples.     

Development of a cloud point extraction and preconcentration method for determination of trace aluminum in mineral waters by FAAS

A cloud point extraction (CPE) method has been developed for the preconcentration of trace aluminum prior to its determination by flame atomic absorption spectrometry (FAAS). The CPE method is based on the complex of Al(III) with Xylidyl Blue (XB) and then entrapped in non-ionic surfactant Triton X-114. The main factors affecting CPE efficiency, such as pH of sample solution, concentration of XB and Triton X-114, equilibration temperature and time, were investigated in detail. An enrichment factor of 50 was obtained for the preconcentration of Al(III) with 50 mL solution. Under the optimal conditions, the detection limit of this method for Al(III) is 1.43 μg L^− 1, and the relative standard deviation is 2.7% at determination of 100 μg L^− 1 Al(III). The proposed method has been applied for determination of trace amount of aluminum in mineral water samples with satisfactory results. Also, the proposed method was applied to the certified reference materials. The results obtained were in good agreement with certified values.     

Cloud point extraction–thermospray flame quartz furnace atomic absorption spectrometry for determination of ultratrace cadmium in water and urine

A simple, low cost and highly sensitive method based on cloud point extraction (CPE) for separation/preconcentration and thermospray flame quartz furnace atomic absorption spectrometry was proposed for the determination of ultratrace cadmium in water and urine samples. The analytical procedure involved the formation of analyte-entrapped surfactant micelles by mixing the analyte solution with an ammonium pyrrolidinedithiocarbamate (APDC) solution and a Triton X-114 solution. When the temperature of the system was higher than the cloud point of Triton X-114, the complex of cadmium-PDC entered the surfactant-rich phase and thus separation of the analyte from the matrix was achieved. Under optimal chemical and instrumental conditions, the limit of detection was 0.04 μg/L for cadmium with a sample volume of 10 mL. The analytical results of cadmium in water and urine samples agreed well with those by ICP-MS.     

Speciation analysis of manganese in tea samples using flame atomic absorption spectrometry after cloud point extraction

The speciation of Mn(II) in tea infusion was studied using cloud point extraction (CPE). In tea infusion, the flavonoid-bound Mn(II) was extracted at pH 5.0 using Triton X-100 (TX-100), the remaining free aquated Mn(II) and weakly-complexed Mn(II) in solution were both chelated with 8-hydroxyquinoline (HOx) and CPE-preconcentrated with TX-100. The enriched analyte was determined by flame AAS. The optimal concentrations for CPE of 0.02 ppm Mn were as follows: TX-100, 0.2% (v/v); HOx, 1.0 × 10⁻⁴ M; NaCl, 1.0% (w/v). LOD was 1.9 μg/L with a preconcentration factor of 10–20. The method was validated using a standard XAD-resin separation procedure and applied to synthetic seawater and CRM samples.     

Cloud point and solid phase extraction of vanadium in surface and bottled mineral water samples using 8-hydroxyquinoline as a complexing reagent

Cloud point extraction (CPE) and solid phase extraction (SPE) methods were developed for the determination of ??g l^?1 of vanadium ions in surface, tap and bottled mineral water samples, based on the rapid reaction of vanadium(V) with 8- hydroxyquinoline (8-quinolinol) at pH 3?C5. Both the sensitive extraction methods were successfully employed for the preconcentration of V in real samples. For CPE, V complexed with 8-quinolinol and then was entrapped in non-ionic surfactant Triton X-114, while for SPE, V was adsorbed on XAD -2 impregnated with 8-quinolinol. The experimental conditions for SPE (pH, eluent, and contact time between the liquid sample and the resin) and CPE (pH of sample solution, concentration of 8- quinolinol and Triton X-114, equilibration temperature and time period for shaking) were investigated in detail. The validity of SPE/CPE of V was checked by certified reference material of water (SRM-1643e). The extracted surfactant-rich phase (200 ??l) was mixed with 200 ??l of HNO₃ in ethanol and this final volume was injected into electrothermal atomic absorption spectrometry with different modifiers. Under these conditions, the preconcentration of 25 ml sample solution allowed the raising of an enrichment factor of 100 and 10 folds for CPE and SPE, respectively. The concentration of V in surface water (river and lake), tap water and bottled mineral water samples was found to be in the range of 1.30?C19.9, 1.05?C5.25 and 0.67?C1.21 ??g l^?1, respectively.     

Cloud point extraction of trace metals from seawater and determination by electrothermal atomic absorption spectrometry with iridium permanent modifier.

A simple method is described for preconcentration and separation of trace metals such as Ag, Co, Cr, Cu, Fe, Mn, Ni and Pb simultaneously from seawater using a cloud point extraction (CPE) procedure. Triton X-114 nonionic surfactant and ammonium pyrrolidine dithiocarbamate (APDC) have been used as an extraction medium and a chelating extractant, respectively. The amounts of Triton X-114 and APDC and the pH value necessary for extraction were carefully optimized. The preconcentration factor of about 200 is achieved for all the studied metals. Electrothermal atomic absorption spectrometry (ETAAS) with an Ir coated graphite tube as permanent chemical modifier has been used for determination. The limits of detection of Ag, Co, Cr, Cu, Fe, Mn, Ni and Pb were 0.003, 0.008, 0.003, 0.006, 0.015, 0.002, 0.009 and 0.01 ng ml-1, respectively. Certified reference materials such as CASS-4 and NASS-5 (seawater) and NIST-1640 (natural water) have been used for validation of the new method. The relative standard deviation (%) obtained for all the metals are in the range 0.8 - 3.6% for natural water and 11-25% for seawater materials, except for Co in NASS-5 for which it was 50%.     

Cloud point preconcentration and flame atomic absorption spectrometric determination of Cd and Pb in human hair

Cloud point methodology has been successfully used for the preconcentration of trace amounts of Cd and Pb as a prior step to their determination by flame atomic absorption spectrometry. O,O-Diethyldithiophosphate and Triton X-114 are used as hydrophobic ligand and non-ionic surfactant, respectively. After phase separation at 40 °C based on cloud point of the mixture, the surfactant-rich phase is diluted with methanol. The enriched analyte in the final solution is determined by flame atomic absorption spectrometry using conventional nebulization. After optimization of the complexation and extraction conditions, enhancement factors of 22 and 43 were obtained for Cd and Pb, respectively. Under the experimental conditions used, preconcentration of only 10 ml of sample in the presence of 0.05% (v/v) Triton X-114 permitted the detection of 0.62 μg l⁻¹ of Cd and 2.86 μg l⁻¹of Pb. The proposed method was applied to the determination of Cd and Pb in human hair samples.     

In situ synthesis and preconcentration of cetylpyridinium complexed hexaiodo platinum nanoparticles from spent automobile catalytic converter leachate using cloud point extraction

In the present study, a green chemistry based cloud point extraction (CPE) method has been developed for the in situ synthesis and preconcentration of cetylpyridinium complexed hexaiodo platinum nanoparticles (Pt-I NP) from the leachate of spent automobile catalytic converter using potassium iodide (KI) and assisted by a combination of cationic and non-ionic surfactants; cetylpyridinium bromide (CPB) and Triton X-114, respectively. The process parameters such as concentrations of hydrochloric acid, platinum, KI, sodium chloride, CPB, Triton X-114; incubation temperature and complexation time on CPE were optimized. The synthesized nanoparticles were characterized by UV–visible spectroscopy (UV–vis), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and zeta potential techniques. The formation of Pt-I NP was followed with UV–vis. The XRD pattern established the tetragonal crystal structure of the produced nanoparticles. The nanoparticles were spherical in shape and the particle size obtained with TEM was about 5.6 nm. Further, the preconcentrated nanoparticles were quantified by continuum source electro-thermal atomic absorption spectrometry (ET-AAS) and a preconcentration factor of 25 was obtained for a reaction volume of 25 mL. The accuracy of the developed method was confirmed by analyzing the certified reference materials such as CCRMP PTM-1a (copper-nickel sulphide matte) and CCRMP PTC-1a (copper-nickel sulphide concentrate). The current CPE protocol demonstrates advantages such as simultaneous synthesis and preconcentration; synthesis at micromolar concentration from metal scrap, higher nanoparticle recovery; biodegradability and biocompatibility of the employed surfactants and dual solubility of the synthesized Pt-I NP. Thus, the developed method can be applied for the separation, large scale synthesis and preconcentration of Pt-I NP from various environmental and industrial wastes, in a single pot.     

Separation and preconcentration of trace amounts of aluminum ions in surface water samples using different analytical techniques

A separation/preconcentration of aluminum (III) (Al³⁺) has been developed to overcome the problem of high matrix species, which may interfere with the determination of trace quantity of Al³⁺ in natural water samples. The separation of Al³⁺ in water samples was carried out from interfering cations by complexing them with 2-methyle 8-hyroxyquinoline (quinaldine) on activated silica. Whereas the separated trace amounts of Al³⁺ was preconcentrated by cloud point extraction (CPE), as prior step to its determination by spectrofluorimetry (SPF) and flame atomic absorption spectrometry (FAAS). The Al³⁺ react with 8-hydroxyquinoline (oxine) and then entrapped in non-ionic surfactant Triton X-114. The main factors affecting CPE efficiency, such as pH of sample solution, concentration of oxine and Triton X-114, equilibration temperature and time period for shaking were investigated in detail. The validity of separation/preconcentration of Al³⁺ was checked by certified reference material of water (SRM-1643e). After optimization of the complexation and extraction conditions, a preconcentration factor of 20 was obtained for Al³⁺ in 10 mL of natural water samples. The relative standard deviation for 6 replicates containing 100 μg L⁻¹ of Al³⁺ was 5.41 and 4.53% for SPF and FAAS, respectively. The proposed method has been applied for determination of trace amount of Al³⁺ in natural water samples with satisfactory results.     

Investigation of analytical performance for rapidly synergistic cloud point extraction of trace amounts of copper combined with spectrophotometric determination

In this work, an improved preconcentration method named as rapidly synergistic cloud point extraction (RS-CPE) was established for copper preconcentration and determination. Non-ionic surfactant Triton X-100 (TX-100) was used as extractant. Octanol worked as cloud point revulsant and synergic reagent, which successfully decreased the cloud point temperature (CPT) of TX-100 to realize the room temperature (about 20°C) CPE without heating. The established RS-CPE pretreatment was simple, rapid and effective. Compared with traditional CPE (about 40 min for heating, incubation and cooling), the extraction time of the proposed method was very short (1 min). The improved extraction technique RS-CPE was combined with traditional spectrophotometer to improve the analytical performance and expand the application of spectrophotometric determination. The influence factors relevant to RS-CPE, such as concentrations of TX-100 and octanol, concentration of chelating agent, pH, conditions of phase separation, salt effect, environmental temperature and instrumental conditions, were studied in detail. Under the optimal conditions, the limit of detection (LOD) for copper was 0.4 μg L(-1), with sensitivity enhancement factor (EF) of 18. The proposed method was applied to the determination of trace copper in real samples and certified samples with satisfactory analytical results.     

Determination of trace vanadium in sea cucumbers by ultrasound-assisted cloud point extraction and graphite furnace atomic absorption spectrometry

An ultrasound-assisted cloud point extraction (CPE) procedure was used for preconcentration and determination of vanadium by graphite furnace atomic absorption spectrometry. The vanadyl(IV) complex with ascorbic acid form a hydrophobic complex with 4-(2-pyridylazo) resorcinol (PAR) in a micelle medium, which is stable under our working conditions, and followed by its extraction into Triton X-100 surfactant-rich phase. The main factors affecting CPE efficiency, such as pH, concentrations of PAR, ascorbic acid and Triton X-100, incubation temperature, frequency and equilibration time of ultrasonic bath were investigated in detail. Under the optimum conditions, preconcentration of 10 mL sample gave a preconcentration factor of 36.4 and a detection limit of 4.0 µg kg^?1. The proposed method was successfully applied to determination of vanadium in sea cucumbers with satisfactory results.     

Cloud point extraction and graphite furnace atomic absorption spectrometry determination of manganese(II) and iron(III) in water samples

Cloud point extraction (CPE) was applied as a preconcentration step prior to graphite furnace atomic absorption spectrometry (GFAAS) determination of manganese(II) and iron(III) in water samples. After complexation with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), the analytes could be quantitatively extracted to the phase rich in the surfactant p-octylpolyethyleneglycolphenylether (Triton X-100) and be concentrated, then determined by GFAAS. The parameters affecting the extraction efficiency, such as solution pH, concentration of PMBP and Triton X-100, equilibration temperature and time, were investigated in detail. Under the optimum conditions, preconcentration of 10 ml of sample solution permitted the detection of 0.02 ng ml(-1) of Mn(II) and 0.08 ng ml(-1) of Fe(III) with enrichment factors of 31 and 25 for Mn(II) and Fe(III), respectively. The proposed method was applied to determination of trace manganese(II) and iron(III) in water samples with satisfactory results.     

Determination of ultra-trace amount methyl-, phenyl- and inorganic mercury in environmental and biological samples by liquid chromatography with inductively coupled plasma mass spectrometry after cloud point extraction preconcentration

The cloud point extraction (CPE) preconcentration of ultra-trace amount of mercury species prior to reverse-phase high performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) detection was studied. Mercury species including methyl-, ethyl-, phenyl- and inorganic mercury were transformed into hydrophobic chelates by reaction with sodium diethyldithiocarbamate, and the hydrophobic chelates were extracted into a surfactant-rich phase of Triton X-114 upon heating in a water bath at 40 °C. Ethylmercury was found partially decomposed during the CPE process, and was not included in the developed method. Various experimental conditions affecting the CPE preconcentration, HPLC separation, and ICP-MS determination were optimized. Under the optimized conditions, detection limits of 13, 8 and 6 ng l⁻¹ (as Hg) were achieved for MeHg⁺, PhHg⁺ and Hg²⁺, respectively. Seven determinations of a standard solution containing the three mercury species each at 0.5 ng ml⁻¹ level produced relative standard deviations of 5.3, 2.3 and 4.4% for MeHg⁺, PhHg⁺ and Hg²⁺, respectively. The developed method was successfully applied for the determination of the three mercury species in environmental water samples and biological samples of human hair and ocean fish.     

Determination of selenium in marine biological tissues by transverse heated electrothermal atomic absorption spectrometry with longitudinal Zeeman background correction and automated ultrasonic slurry sampling.

A fast, sensitive, and reliable method for determination of selenium in marine biological tissues by electrothermal atomic absorption spectrometry with slurry sampling was developed. Slurries were prepared from fresh and frozen seafood samples that were previously homogenized, dried, and ground; particle sizes <100 microm were taken for analysis. A 3% (v/v) HNO3 solution containing 0.01% (v/v) Triton X-100 was used as slurry diluent. Slurries were mixed on an automated ultrasonic slurry sampler at 20% amplitude for 30 s just before an aliquot was injected into the furnace. The method was successfully validated against the following certified reference materials: NRCC CRM DORM-2 (Dogfish muscle); NRCC CRM TORT-2 (Lobster hepatopancreas); NRCC CRM DOLT-2 (Dogfish liver); and BCR CRM 278 (Mussel tissue), and was subsequently applied to determination of Se in 10 marine biological samples. The influences of the drying procedure (oven-, microwave-, and freeze-drying), matrix modifier amount, mass of solid material in cup, and pipetting sequence are discussed. The limit of determination of Se was 0.16 microg/g and the repeatability, estimated as between-batch precision, was in the range of 4-8%. Se contents in the samples ranged from 0.6 to 2.8 microg/g. The proposed method should be useful for fast assessment of the daily dietary intake of Se.     

Cloud point extraction of aluminum (III) in water samples and determination by electrothermal atomic absorption spectrometry,flame atomic absorption spectrometry and UV-visible spectrophotometry

Cloud point extraction was applied as a preconcentration step for the determination of trace level of Al(III) in water samples with electrothermal atomic absorption spectrometry (ETAAS), flame atomic absorption spectrometry (FAAS) and UV-visible spectrophotometry. The aluminum was extracted as aluminum-Eriochrome Cyanine R (ECR) complex, at pH 6 by micelles of the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114). The investigations showed that the same CPE procedure can be used for different detection techniques. The results obtained from these techniques were evaluated. Under the optimal conditions, limit of detection obtained with ETAAS, FAAS and UV-visible spectrophotometry were 0.03 ng mL^?1, 0.06 µg mL^?1 and 0.01 µg mL^?1, respectively. The accuracy of the procedure was tested by analysing certified reference material. The method was successfully applied to determination of aluminum in water samples and dialysis fluid.     

The application of cloud point preconcentration for the determination of Cu in real samples by flame atomic absorption spectrometry

A simple and practical preconcentration method using cloud point approach is proposed for the extraction and preconcentration of Cu (II). The analyte in the initial aqueous solution, acidified with HCl, is complexed with O,O-diethyldithiophosphate and Triton X-100 is added as a surfactant. After phase separation at 40°C based on cloud point of the mixture and dilution of the surfactant-rich phase with methanol, the enriched analyte is determined by flame atomic absorption spectrometry using conventional nebulization and the analytical wavelength used is 324.8 nm. The variables affecting the complexation and extraction steps were optimized. Under optimum conditions, preconcentration of 10 ml of sample in the presence of 0.1% (v/v) Triton X-100 permitted the detection of 0.94 ng ml⁻¹ of Cu. Analytical graphs were rectilinear in the concentration range of 5-200 ng ml⁻¹ and relative standard deviations were lower than 3%. The method affords recoveries in the range 97-101%. The method was successfully applied to the determination of Cu in drinking and rainwater, serum and human hair samples.     

Determination of bisphenol A and naphthols in river water samples by capillary zone electrophoresis after cloud point extraction

As a first attempt, cloud point extraction (CPE) was developed to preconcentrate bisphenol A (BPA), α-naphthol and β-naphthol prior to performing capillary zone electrophoresis (CZE) analysis. The parameters influencing the CPE efficiency, such as Triton X-114 concentrations, pH value, extraction time and temperature were systematically evaluated.After diluting with acetonitrile, the surfactant-rich phase of CPE can be injected directly into the CE instrument. The CZE baseline separation was achieved with running buffer (pH 9.5) composed of 50 mM sodium tetraborate in 30% (v/v) methanol, and an applied voltage of 25 kV. Under the optimized CPE and CZE conditions, an preconcentration factor of 50 times could be obtained and the limit of quantification for the three analytes were found to be 1.67 μg L⁻¹, 0.80 μg L⁻¹ and 0.67 μg L⁻¹ for BPA, α-naphthol and β-naphthol, respectively. The proposed methods have shown to be a green, rapid and effective approach for determination of three analytes present in river water samples.     

Determination of cadmium in rice and water by tungsten coil electrothermal vaporization-atomic fluorescence spectrometry and tungsten coil electrothermal atomic absorption spectrometry after cloud point extraction

In this work, the microsampling nature of tungsten coil electrothermal vaporization Ar/H₂ flame atomic fluorescence spectrometry (W-coil ETV-AFS) as well as tungsten coil electrothermal atomic absorption spectrometry (W-coil ET-AAS) was used with cloud point extraction (CPE) for the ultrasensitive determination of cadmium in rice and water samples. When the temperature of the extraction system is higher than the cloud point temperature of the selected surfactant Triton X-114, the complex of cadmium with dithizone can be quantitatively extracted into the surfactant-rich phase and subsequently separated from the bulk aqueous phase by centrifugation. The main factors affecting the CPE, such as concentration of Triton X-114 and dithizone, pH, equilibration temperature and incubation time, were optimized for the best extract efficiency. Under the optimal conditions, the limits of detection for cadmium by W-coil ETV-AFS and W-coil ET-AAS were 0.01 and 0.03 μg L⁻¹, with sensitivity enhancement factors of 152 and 93, respectively. The proposed methods were applied to the determination of cadmium in certified reference rice and water samples with analytical results in good agreement with certified values.     

A rapid solid sampling method for determination of nickel and copper along human hair by ETAAS

A procedure for copper and nickel determination in scalp hair by solid sampling electrothermal atomic absorption spectrometric method was described. The hair samples (0.02 to 0.4 mg) were inserted directly on the platforms of solid sampling autosampler. The effects of pyrolysis temperature, atomization temperature, the amount of sample as well as addition of a modifier (Pd/Mg) and/or auxiliary digesting agents (hydrogen peroxide and nitric acid) and/or a surfactant (Triton X-100) on the determination of copper and nickel by solid sampling atomic absorption spectrometry were investigated. After optimization of parameters, the average recoveries of copper in two different certified reference hair samples were 105.7 and 97.6%. The recoveries of nickel in the both certified reference hair samples were in 95.2 and 96.4%. The limits of detection (3σ, N = 10) for copper and nickel were 22 ng/g and 35 ng/g, respectively. Heterogenous distribution of analyte in microscale for segmental analysis could be determined which is important to know that analyte quantity and time of poisoning of a person was exposed. For this purpose, 0.5 cm of pieces were cut along one or a few close strands and analyzed by solid sampling. This process could not be performed by wet-digestion method because 50 mg of sample is needed each time. Finally, the method was applied for the determination of copper and nickel concentrations in the hairs of different persons.     

Cloud point extraction, preconcentration and simultaneous spectrophotometric determination of nickel and cobalt in water samples

Cloud point extraction has been used for the preconcentration and simultaneous spectrophotometric determination of nickel and cobalt after the formation of a complex with 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA), and latter analysis by spectrophotometer using Triton X-114 as surfactant. The parameters affecting the separation phase and detection process were optimized. Under the optimum experimental conditions (i.e. pH=5, 0.07 mM ACDA, Triton X-114=0.25% (w/v)), calibration graphs were linear in the range of 20-500 and 20-200 microg l(-1) with detection limits of 10 and 7.5 microg l(-1) for Ni and Co, respectively. The method was applied to the determination of Ni and Co in natural and waste water samples with satisfactory results.