Cloud point extraction combined with electrothermal atomic absorption spectrometry for the speciation of antimony(III) and antimony(V) in food packaging materials.
ABSTRACT A simple, sensitive method for the speciation of inorganic antimony by cloud point extraction combined with electrothermal atomic absorption spectrometry (ETAAS) is presented and evaluated. The method based on the fact that formation of a hydrophobic complex of antimony(III) with ammonium pyrrolidine dithiocarbamate (APDC) at pH 5.0 and subsequently the hydrophobic complex enter into surfactant-rich phase, whereas antimony(V) remained in aqueous solutions. Antimony(III) in surfactant-rich phase was analyzed by ETAAS after dilution by 0.2 mL nitric acid in methanol (0.1M), and antimony(V) was calculated by subtracting antimony(III) from the total antimony after reducing antimony(V) to antimony(III) by l-cysteine. The main factors affecting the cloud point extraction, such as pH, concentration of APDC and Triton X-114, equilibrium temperature and incubation time, sample volume were investigated in detail. Under the optimum conditions, the detection limit (3 sigma) of the proposed method was 0.02 ng mL(-1) for antimony(III), and the relative standard deviation was 7.8% (c=1.0 ng mL(-1), n=7). The proposed method was successfully applied to speciation of inorganic antimony in the leaching solutions of different food packaging materials with satisfactory results.
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ABSTRACT: On-vial immobilized CdSe quantum dots (QDs) are applied for the first time as chemiluminescent probes for the detection of trace metal ions. Among 17 metal ions tested, inhibition of the chemiluminescence when CdSe QDs are oxidized by H2O2 was observed for Sb, Se and Cu. Liquid-liquid-liquid microextraction was implemented in order to improve the selectivity and sensitivity of the chemiluminescent assay. Factors influencing both the CdSe QDs/H2O2 chemiluminescent system and microextraction process were optimized for ultrasensitive detection of Sb(III) and total Sb. In order to investigate the mechanism by which Sb ions inhibit the chemiluminescence of the CdSe QDs/H2O2 system, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption and fluorescence measurements were performed. The selection of the appropriate CdSe QDs capping ligand was found to be a critical issue. Immobilization of QDs caused the chemiluminescence signal to be enhanced by a factor of 100 as compared to experiments carried out with QDs dispersed in the bulk aqueous phase. Under optimized conditions, the detection limit was 6ngL(-1) Sb and the repeatability expressed as relative standard deviation (N=7) was about 1.3%. An enrichment factor of 95 was achieved within only 3min of microextraction. Several water samples including drinking, spring, and river waters were analyzed. The proposed method was validated against CRM NWTM-27.2 fortified lake water, and a recovery study was performed with different types of water samples. Sb recoveries ranged from 94 to 105%. A fast, miniaturized and relatively inexpensive assay for selective and sensitive detection of Sb(III) and total Sb in waters is accomplished.Analytica chimica acta 07/2013; 788C:114-121. · 4.31 Impact Factor
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ABSTRACT: Cloud-point extraction (CPE), an easy, safe, environmentally friendly, rapid and inexpensive methodology for preconcentration and separation of trace metals from aqueous solutions has recently become an attractive area of research and an alternative to liquid-liquid extraction. Moreover, it provides results comparable to those obtained with other separation techniques and has a greater potential to be explored in improving detection limits and other analytical characteristics over other methods. A few reviews have been published covering different aspects of the CPE procedure and its relevant applications, such as the phenomenon of clouding, the application in the extraction of trace inorganic and organic materials, as well as pesticides and protein substrates from different sources, or incorporation of CPE into an FIA system. This review focuses on general properties of the most frequently used organic ligands in cloud-point extraction and on literature data (from 2000 to 2012) concerning the use of modern techniques in determination of metal ions' content in various materials. The article is divided according to the class of organic ligands to be used in CPE.Talanta 06/2013; 110:202-28. · 3.50 Impact Factor
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ABSTRACT: Olive mill wastewater (OMW) causes many environmental problems, mainly in the Mediterranean area. The phenolic content of OMW is principally responsible for the phytotoxicity and microbial growth inhibitory effects. However, these effluents can be considered as a source of powerful natural antioxidants. Cloud point extraction method was used to recover and separate phenolic compounds from pretreated olive mill wastewater. The OMW samples were ultrafiltered on 50 kDa polyethersulfone (PES) membrane. The Triton X-100 was used as surfactant at concentrations ranging from 1 to 10% (w/w). Three temperatures (70 C, 80 C and 90 C) above the cloud point temperature of the surfactant were tested. After 30 min at the desired temperature the mixture form two phases: a diluted phase and a concentrated phase called coacervate. The efficiency of the extraction was evaluated by determining the phenolic compounds concentration and the volume of the both phases. The obtained results show the possibility to extract up to 66.5 AE 3.2% of the phenolic content from OMW using one step CPE. The highest yield was obtained when using 10% of Triton X-100 at 90 C. The results obtained for volume fraction (f c) and rate of recovery (R%), by response surface methodology were in agreement with the experimental data. The results show that the CPE can be an efficient alternative to the classic methods of extraction since it can offer a mixture of natural antioxidants suitable for pharmaceutical, cosmetic or food applications. ã 2014 Published by Elsevier Ltd.Journal of Environmental Chemical Engineering. 07/2014; 2:1480–1486.