Determination of trace aluminum in biological and water samples by cloud point extraction preconcentration and graphite furnace atomic absorption spectrometry detection

A cloud point extraction (CPE) method for the preconcentration of trace aluminum prior to its determination by graphite furnace atomic absorption spectrometry (GFAAS) has been developed. The CPE method is based on the complex of Al(III) with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), and then entrapped in non-ionic surfactant Triton X-114. PMBP was used not only as chelating reagent in CPE preconcentration, but also as chemical modifier in GFAAS determination. The main factors affecting CPE efficiency, such as pH of sample solution, concentration of PMBP and Triton X-114, equilibration temperature and time, were investigated in detail. An enrichment factor of 37 was obtained for the preconcentration of Al(III) with 10 mL solution. Under the optimal conditions, the detection limit of this method for Al(III) is 0.09 ng mL(-1), and the relative standard deviation is 4.7% at 10 ng mL(-1) Al(III) level (n=7). The proposed method has been applied for determination of trace amount of aluminum in biological and water samples with satisfactory results.     

Flame atomic absorption spectrometric determination of trace quantities of cadmium in water samples after cloud point extraction in Triton X-114 without added chelating agents

A new micell-mediated phase separation method for preconcentration of ultra-trace quantities of cadmium as a prior step to its determination by flame atomic absorption spectrometry has been developed. The method is based on the cloud point extraction (CPE) of cadmium in iodide media with Triton X-114 in the absence of any chelating agent. The optimal extraction and reaction conditions (e.g., acid concentration, iodide concentration, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 3-300 ng mL(-1) of cadmium. The detection limit of the method is 1.0 ng mL(-1) of cadmium. The interference effect of some anions and cations was also tested. The method was applied to the determination of cadmium in tap water, waste water, and sea water samples.     

Determination of trace nickel in water samples by cloud point extraction preconcentration coupled with graphite furnace atomic absorption spectrometry

A new method based on the cloud point extraction (CPE) preconcentration and graphite furnace atomic absorption spectrometry (GFAAS) detection was proposed for the determination of trace nickel in water samples. When the micelle solution temperature is higher than the cloud point of surfactant p-octylpolyethyleneglycolphenyether (Triton X-100), the complex of Ni2+ with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) could enter surfactant-rich phase and be concentrated, then determined by GFAAS. The main factors affecting the cloud point extraction were investigated in detail. An enrichment factor of 27 was obtained for the preconcentration of Ni2+ with 10 mL solution. Under the optimal conditions, the detection limit of Ni2+ is 0.12 ng mL(-1) with R.S.D. of 4.3% (n = 10, c = 100 ng mL(-1)). The proposed method was applied to determination of trace nickel in water samples with satisfactory results.     

Development of a cloud point extraction-spectrofluorimetric method for trace copper(II) determination in water samples and parenteral solutions

A simple and efficient cloud point extraction-spectrofluorimetric method for the determination of copper(II) in different samples has been proposed. The procedure is based on the oxidation of thiamine with copper(II) to form highly fluorescent thiochrome, its extraction to Triton X-114 micelles and spectrofluorimetric determination. The variables affecting the analytical performance were studied and optimized. The calibration graphs using the preconcentration system for copper were linear over the range 1.0-250 ng ml-1 with limit of detection of 0.29 ng ml-1. Relative standard deviation for five replicate determinations of copper at 100 ng ml-1 concentration level was 2.12%. Average recoveries between 94 and 105% were obtained for spiked samples. The method has been applied to water samples and parenteral solutions and the amounts of copper found are very similar to those obtained by a standard method.     

Spectrophotometric determination of mercury in water samples after cloud point extraction using nonionic surfactant Triton X-114

A cloud point extraction process using the nonionic surfactant Triton X-114 for extracting mercury from aqueous solutions was investigated. The method is based on the complexation reaction of Hg(II) with Thio-Michler's Ketone (TMK) and micelle-mediated extraction of the complex. The optimal extraction and reaction conditions (e.g., pH, reagent concentration, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range) were obtained. Linearity was obeyed in the range of 5.0-80.0 ng mL(-1) of Hg(II) ion. The detection limit of the method was 0.83 ng mL(-1) of Hg(II) ion. The interference effect of some anions and cations was also tested. The method was applied to the determination of mercury in water samples.     

Determination of trace bismuth in human serum by cloud point extraction coupled flow injection inductively coupled plasma optical emission spectrometry

A cloud point extraction method for the preconcentration of ultra-trace bismuth in human serum prior to its determination by inductively coupled plasma optical emission spectrometry had been developed in this paper. The cloud point extraction method was based on the complex of Bi(III) with 8-hydroxyquinoline and Triton X-114 was used as non-ionic surfactant. The main factors affecting cloud point extraction efficiency, such as pH of solution, concentration of complexing agent, concentration of non-ionic surfactant, equilibration temperature and time were investigated in detail. An enrichment factor of 81 was obtained for the preconcentration of Bi(III) with 25 mL solution. Under the optimal conditions, the detection limit of Bi(III) is 0.12 μg L⁻¹. The relative standard deviation (n = 7) of determination was 2.3%, values of recovery of bismuth were from 92.3% to 94.7% for three samples. This method is simple, accurate, sensitive and can be applied to the determination trace bismuth in human serum.     

Cloud point extraction for the determination of copper, nickel and cobalt ions in environmental samples by flame atomic absorption spectrometry

A cloud point extraction procedure was presented for the preconcentration of copper, nickel and cobalt ions in various samples. After complexation with methyl-2-pyridylketone oxime (MPKO) in basic medium, analyte ions are quantitatively extracted to the phase rich in Triton X-114 following centrifugation. 1.0 mol L⁻¹ HNO₃ nitric acid in methanol was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The adopted concentrations for MPKO, Triton X-114 and HNO₃, bath temperature, centrifuge rate and time were optimized. Detection limits (3 SDb/m) of 1.6, 2.1 and 1.9 ng mL⁻¹ for Cu²⁺, Co²⁺ and Ni²⁺ along with preconcentration factors of 30 and for these ions and enrichment factor of 65, 58 and 67 for Cu²⁺, Ni²⁺ and Co²⁺, respectively. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed procedure was applied to the analysis of biological, natural and wastewater, soil and blood samples.     

Development of cloud point extraction for simultaneous extraction and determination of gold and palladium using ICP-OES

Cloud point method was applied for the simultaneous extraction and preconcentration of trace amounts of gold and palladium. The extraction of analytes was performed in the presence of 1,8-diamino-4,5-dihydroxy anthraquinone as chelating agent and Triton X-114 as a non-ionic surfactant. After phase separation, the surfactant-rich phase was diluted with concentrated HNO(3) (65%, w/w) and the analytes concentrations were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The variables affecting the complexation and extraction conditions were optimized and under the optimum conditions (i.e. pH 6.5, 2.2 x 10(-4) mol l(-1) chelating agent, 0.15% (w/v) of Triton X-114, equilibration temperature 55 degrees C, centrifuge at 3500 rpm), quantitative extraction of Au(III) and Pd(II) from 100 ml of the aqueous solution was performed. The calibration curves were linear in the range of 0.5-1000 microg l(-1) with detection limits of 0.5 and 0.3 microg l(-1) and the enrichment factors were 8.6 and 20.2 for Au and Pd, respectively. Also the precision (%RSD) for eight replicate determinations of the analytes was better than 5%. Finally, the proposed method was successfully applied for the determination of Au and Pd in mine stones and standard reference materials (SRM).     

Nonaqueous catalytic fluorometric trace determination of vanadium based on the pyronine B-hydrogen peroxide reaction and flow injection after cloud point extraction

The catalytic effect of vanadium on the pyronine B-H2O2 system is examined. Enhancement of the catalytic reaction rate along with the efficiency and selectivity against vanadium is achieved in a formic acid environment in the presence of a nonionic surfactant (Triton X-114). Elimination of drastic interference caused by inorganic acids and aqueous matrix along with a 50-fold preconcentration of vanadium are facilitated through cloud point extraction of its neutral complex with 8-quinolinol in an acidic solution. Subsequent flow injection analysis (FIA) with fluorometric detection renders the proposed method ideal for selective and cost-effective determination of as little as 0.020 microng L(-1) vanadium in environmental, biological, and food substrates. The preconcentration step can be applied simultaneously to multiple samples, allowing for massive preparation prior to analysis, compensating, thus, for the time-consuming procedure.     

Novel analytical reagent for the application of cloud-point preconcentration and flame atomic absorption spectrometric determination of nickel in natural water samples

Cloud-point extraction was applied as a preconcentration of nickel after formation of complex with newly synthesized N-quino[8,7-b]azin-5-yl-2,3,5,6,8,9,11,12octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecin-15-yl-methanimine, and later determined by flame atomic absorption spectrometry (FAAS) using octyl phenoxy polyethoxy ethanol (Triton X-114) as surfactant. Nickel was complexed with N-quino[8,7-b]azin-5-yl-2,3,5,6,8,9,11,12octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecin-15-yl-methanimine in an aqueous phase and was kept for 15 min in a thermo-stated bath at 40 degrees C. Separation of the two phases was accomplished by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud-point extraction were evaluated, optimized and successfully applied to the nickel determination in various water samples. Under the optimized conditions, the preconcentration system of 100 ml sample permitted an enhancement factor of 50-fold. The detailed study of various interferences made the method more selective. The detection limits obtained under optimal condition was 0.042 ngml(-1). The extraction efficiency was investigated at different nickel concentrations (20-80 ngml(-1)) and good recoveries (99.05-99.93%) were obtained using present method. The proposed method has been applied successfully for the determination of nickel in various water samples and compared with reported method in terms of Student's t-test and variance ratio f-test which indicate the significance of present method over reported and spectrophotometric methods at 95% confidence level.     

Cloud point extraction and flame atomic absorption spectrometry combination for copper(II) ion in environmental and biological samples

A cloud point extraction procedure was presented for the preconcentration of copper(II) ion in various samples. After complexation by 4-(phenyl diazenyl) benzene-1,3-diamine (PDBDM) (chrysoidine), copper(II) ions were quantitatively recovered in Triton X-114 after centrifugation. 0.5 ml of methanol acidified with 1.0 mol L⁻¹ HNO₃ was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The influence of analytical parameters including ligand, Triton X-114 and HNO₃ concentrations, bath temperature, heating time, centrifuge rate and time were optimized. The effect of the matrix ions on the recovery of copper(II) ions was investigated. The detection limit (3S.D._b/m, n = 10) of 0.6 ng mL⁻¹ along with preconcentration factor of 30 and enrichment factor of 41.1 with R.S.D. of 1.0% for Cu was achieved. The proposed procedure was applied to the analysis of various environmental and biological samples.     

Speciation determination of chromium(III) and (VI) using preconcentration cloud point extraction with flame atomic absorption spectrometry (FAAS)

bis-[2-Hydroxy-1-naphthaldehyde] thiourea was synthesized and preconcentration cloud point extraction (CPE) for speciation determination of chromium(III) and (VI) in various environmental samples with flame atomic absorption spectrometry (FAAS) has been developed. Chromium(III) complexes with bis-[2-hydroxynaphthaldehyde] thiourea is subsequently entrapped in the surfactant micelles. After complexation of chromium(III) with reagent, the analyte was quantitatively extracted to the surfactant-rich phase in the non-ionic surfactant Triton X-100 after centrifugation. The effect of pH, concentration of chelating agent, surfactant, equilibration temperature and time on CPE was studied. The relative standard deviation was 2.13% and the limits of detection were around 0.18 μg L⁻¹.     

Simultaneous preconcentration and determination of U(VI), Th(IV), Zr(IV) and Hf(IV) ions in aqueous samples using micelle-mediated extraction coupled to inductively coupled plasma-optical emission spectrometry

A simple cloud point extraction method followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for simultaneous preconcentration and determination of trace amounts of U(VI), Th(IV), Zr(IV) and Hf(IV) ions in aqueous samples. The metal ions in 50 ml of aqueous solution (containing 0.1 M sodium acetate, pH 6.0) were formed complexes with dibenzoylmethane (DBM). Then, Triton X-114 (0.2%, w/v) was added to the solution. By increasing the temperature of the solution up to 50 degrees C, a phase separation occurred. After centrifugation at 4000 rpm for 6 min, the surfactant-rich phase (sediment phase) was diluted with 1.0 ml of 20:80 (v/v) of methanol/1 M HNO(3). The metal ions were then determined using ICP-OES. Finally, the main factors affecting the cloud point extraction were evaluated and optimized. Under optimized conditions, enhancement factors in the range of 37.0-43.6 were obtained. The calibration graphs were linear in the range of 0.5-1500 microg l(-1) for Th and Zr, 0.5-500 microg l(-1) for Hf and 2.5-1240 microg l(-1) for U with correlation coefficients (r(2)) better than 0.9926. The detection limits were between 0.1 and 1.0 microg l(-1) and the R.S.D. values for seven replicates were lower than 6.1%.     

Speciation of chromium in water samples with cloud point extraction separation and preconcentration and determination by graphite furnace atomic absorption spectrometry

A novel method has been developed for the speciation of chromium in natural water samples based on cloud point extraction (CPE) separation and preconcentration, and determination by graphite furnace atomic absorption spectrometry (GFAAS). In this method, Cr(III) reacts with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (PMBP) yielding a hydrophobic complex, which then is entrapped in the 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. PMBP was used not only as chelating reagent in CPE procedure, but also as chemical modifier in GFAAS determination of chromium. The detection limit for Cr(III) was 21 ng L(-1) with an enrichment factor of 42, and the relative standard deviation was 3.5% (n=7, c=10 ng mL(-1)). The proposed method has been applied to the speciation of chromium in natural water samples with satisfactory results.     

Ultra-trace determination of silver in water samples by electrothermal atomic absorption spectrometry after preconcentration with a ligand-less cloud point extraction methodology

A very simple and ligand-less cloud point extraction (CPE) methodology for the preconcentration of ultra-trace amounts of silver as a prior step to its determination by electrothermal atomic absorption spectrometry (ETAAS) has been developed. The method is based on the extraction of silver at pH 9 by using non-ionic surfactant polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) without adding any chelating agent. Several important variables that affect the CPE efficiency and ETAAS signal were investigated and optimized. The preconcentration of 15 ml sample solution allowed us to achieve an enhancement factor of 60. The calibration graph using the preconcentration system was linear in the range of 5-100 ngl(-1) with a correlation coefficient of 0.9991. The lower limit of detection (3s) obtained in the optimal conditions was 1.2 ngl(-1). The relative standard deviation (R.S.D.) for eight replicate determinations at 30 ngl(-1) Ag level was 4.2%. The proposed method was successfully applied to the ultra-trace determination of silver in water samples.     

Speciation analysis of silver nanoparticles and silver ions in antibacterial products and environmental waters via cloud point extraction-based separation

The rapid growth in commercial use of silver nanoparticles (AgNPs) will inevitably increase silver exposure in the environment and the general population. As the fate and toxic effects of AgNPs is related to the Ag(+) released from AgNPs and the transformation of Ag(+) into AgNPs, it is of great importance to develop methods for speciation analysis of AgNPs and Ag(+). This study reports the use of Triton X-114-based cloud point extraction as an efficient separation approach for the speciation analysis of AgNPs and Ag(+) in antibacterial products and environmental waters. AgNPs were quantified by determining the Ag content in the Triton X-114-rich phase with inductively coupled plasma mass spectrometry (ICPMS) after microwave digestion. The concentration of total Ag(+), which consists of the AgNP adsorbed, the matrix associated, and the freely dissolved, was obtained by subtracting the AgNP content from the total silver content that was determined by ICPMS after digestion. The limits of quantification (S/N = 10) for antibacterial products were 0.4 μg/kg and 0.2 μg/kg for AgNPs and total silver, respectively. The reliable quantification limit was 3 μg/kg for total Ag(+). The presence of Ag(+) at concentrations up to 2-fold that of AgNPs caused no effects on the determination of AgNPs. In the cloud point extraction of AgNPs in antibacterial products, the spiked recoveries of AgNPs were in the range of 71.7-103% while the extraction efficiencies of Ag(+) were in the range of 1.2-10%. The possible coextracted other silver containing nanoparticles in the cloud point extraction of AgNPs were distinguished by transmission electron microscopy (TEM), scanning electron microscopy (SEM)- energy dispersive spectroscopy (EDS), and UV-vis spectrum. Real sample analysis indicated that even though the manufacturers claimed nanosilver products, AgNPs were detected only in three of the six tested antibacterial products.     

Development of a cloud-point extraction method for copper and nickel determination in food samples

A new, simple and versatile cloud-point extraction (CPE) methodology has been developed for the separation and preconcentration of copper and nickel. The metals in the initial aqueous solution were complexed with 2-(2'-benzothiazolylazo)-5-(N,N-diethyl)aminophenol (BDAP) and Triton X-114 was added as surfactant. Dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the copper and nickel contents were measured by flame atomic absorption spectrometry. The variables affecting the cloud-point extraction were optimized using a Box-Behnken design. Under the optimum experimental conditions, enrichment factors of 29 and 25 were achieved for copper and nickel, respectively. The accuracy of the method was evaluated and confirmed by analysis of the followings certified reference materials: Apple Leaves, Spinach Leaves and Tomato Leaves. The limits of detection expressed to solid sample analysis were 0.1 microg g(-1) (Cu) and 0.4 microg g(-1) (Ni). The precision for 10 replicate measurements of 75 microg L(-1) Cu or Ni was 6.4 and 1.0, respectively. The method has been successfully applied to the analysis of food samples.     

A solid phase extraction procedure for Fe3+, Cu2+ and Zn2+ ions on 2-phenyl-1H-benzo[d] imidazole loaded on Triton X-100-coated polyvinyl chloride

A new and efficient solid phase extraction method is described for the preconcentration of trace heavy metal ions. The method is based on the adsorption of Fe(3+), Cu(2+) and Zn(2+) on 2-phenyl-1H-benzo[d] imidazole (PHBI) loaded on Triton X-100-coated polyvinyl chloride (PVC). The influences of the analytical parameters including pH and sample volume were investigated. Common coexisting ions did not interfere on the separation and determination of analytes under study. The adsorbed analytes were desorbed by using 5 mL of 4 mol L(-1) nitric acid. The preconcentration factor is 90. The detection limits (3 sigma) were in the range of 0.95-1 microg L(-1). The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be more than 2.7 mg of ions per gram of sorbent. The recoveries of analytes were generally higher than 95%. The relative standard deviations (R.S.D.s) were generally lower than 4%. The method has been successfully applied to some real samples.     

Applicability of cloud point extraction coupled with microwave-assisted back-extraction to the determination of organophosphorous pesticides in human urine by gas chromatography with flame photometry detection

A procedure for the determination of organophosphorous pesticides (OPPs) - phorate, diazinon, parathion-methyl, fenthion and quinalphos - in human urine was developed using the cloud point extraction of nonionic surfactant (Triton X-114) coupled with microwave-assisted back-extraction prior to gas chromatography with flame photometry detection (GC-FPD) analysis. The upper organic solution obtained from back-extraction was centrifugated simply for further cleanup for the sake of automatic injection. A preconcentration factor of 50 was obtained for these five OPPs extracted from only 10 mL of a sample. The limits of detection (LODs) were 0.07 ng mL(-1) for phorate, fenthion and quinalphos, 0.04 ng mL(-1) for diazinon and 0.08 ng mL(-1) for parathion-methyl. The limits of quantification (LOQs) were 0.21, 0.12, 0.24, 0.21 and 0.21 ng mL(-1), respectively. Accuracy of the method was evaluated by bias, which ranged from +6.85 to -14.68%. Precision was also good; the relative standard deviations (R.S.D.s) were less than 9%. The method showed to be potential for biological monitoring.     

Chemometric analytical approach for the cloud point extraction and inductively coupled plasma mass spectrometric determination of zinc oxide nanoparticles in water samples

Cloud point extraction (CPE) with inductively coupled plasma mass spectrometry (ICPMS) was applied to the analysis of zinc oxide nanoparticles (ZnO NPs, mean diameter ～40 nm) in water and wastewater samples. Five CPE factors, surfactant (Triton X-114 (TX-114)) concentration, pH, ionic strength, incubation temperature, and incubation time, were investigated and optimized by orthogonal array design (OAD). A three-level OAD, OA(27) (3(13)) matrix was employed in which the effects of the factors and their contributions to the extraction efficiency were quantitatively assessed by the analysis of variance (ANOVA). Based on the analysis, the best extraction efficiency (87.3%) was obtained at 0.25% (w/v) of TX-114, pH = 10, salt content of 15 mM NaCl, incubation temperature of 45 °C, and incubation time of 30 min. The results showed that surfactant concentration, pH, incubation time, and ionic strength exert significant effects on the extraction efficiency. Preconcentration factors of 62 and 220 were obtained with 0.25 and 0.05% (w/v) TX-114, respectively. The relative recoveries of ZnO NPs from different environmental waters were in the range 64-123% at 0.5-100 μg/L spiked levels. The ZnO NPs extracted into the TX-114-rich phase were characterized by transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDS) and UV-visible spectrometry. Based on the results, no significant changes in size and shape of NPs were observed compared to those in the water before extraction. The extracted ZnO NPs were determined after microwave digestion by ICPMS. A detection limit of 0.05 μg/L was achieved for ZnO NPs. The optimized conditions were successfully applied to the analysis of ZnO NPs in water samples.