A simple and efficient approach for preconcentration of some heavy metals in cosmetic products before their determinations by flame atomic absorption spectrometry
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In the current study, a simple and efficient analytical method for preconcentration and determination of Cd(II), Pb(II), and Sn(II) in some cosmetic samples, using ultrasonic assisted-cloud point extraction and flame atomic absorption spectrometry, was developed. The method is based on the ternary complex formations of Sn(II), Pb(II), and Cd(II), which are available in the form of neutral and/or anionic hydroxo complexes (Sn(OH)$_{3}^{-}$, Pb(OH)$_{3}^{-}$, Cd(OH)$_{2}$, and/or Cd(OH)$_{3}^{-})$, with Victoria Pure Blue BO (VPB$^{+})$ in the presence of cetylpyridinium chloride at pH 8.5, and then extraction of the formed ternary complexes into the micellar phase of polyoxyethylene sorbitan monostearate (Tween 60). Using the optimized conditions, a linear relationship was observed in the ranges of 12-330 $\mu $g L$^{-1}$ for Cd(II), 4-200 $\mu $g L$^{-1}$ for Pb(II), and 1-275 $\mu $g L$^{-1}$ for Sn(II). The detection limits for Cd(II), Pb(II), and Sn(II), respectively, were 3.70, 1.35, and 0.45 $\mu $g L$^{-1}$, with a preconcentration factor of 50, and the precision as relative standard deviations was lower than 4.2% for each analyte. The validity was verified by analysis of two certified reference materials. Finally, the method was successfully applied to the determination of these metals in various cosmetic samples.Keywords:
Cetylpyridinium chloride
Cloud point
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A sensitive and simple cloud point extraction method was developed for simultaneous separation and preconcentration of cadmium and copper prior to their determination by flame atomic absorption spectrometry. 4-phenyl-3-thiosemicarbazide was used as complexing agent and the cadmium and copper complexes were extracted from the aqueous phase by Triton X-114 surfactant. The effects of parameters such as sample pH, ligand amount, concentration of surfactant, incubation temperature and time were optimized. For 20 mL of preconcentrated solution, the detection limits (3σ) were 0.20 and 0.49 μg L−1, and the enrichment factors were 20.7 and 19.9 for Cd(II) and Cu(II), respectively. In order to verify the accuracy of the developed method, certified reference materials (SLRS-5 river water and SPS-SW2 Batch 127 surface water) were analysed. Results obtained were in good agreement with the certified values. The proposed method was applied to tap water, river water and seawater samples with satisfactory results.
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An analytical procedure based on microwave-assisted digestion with diluted acid and a double cloud point extraction is proposed for nickel determination in plant materials by flame atomic absorption spectrometry. Extraction in micellar medium was successfully applied for sample clean up, aiming to remove organic species containing phosphorous that caused spectral interferences by structured background attributed to the formation of PO species in the flame. Cloud point extraction of nickel complexes formed with 1,2-thiazolylazo-2-naphthol was explored for pre-concentration, with enrichment factor estimated as 30, detection limit of 5 µg L-1 (99.7% confidence level) and linear response up to 80 µg L-1. The accuracy of the procedure was evaluated by nickel determinations in reference materials and the results agreed with the certified values at the 95% confidence level.
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The purpose of this study was to determine the cloud point of an amphiphilic drug and to search for means to boost or suppress the cloud point, used in pharmaceutical formulations. Organic compounds (amino acids, saccharides, alcohols, surfactants, and polymers), which are used as pharmaceutical excipients, were tested to demonstrate their effect on the cloud point of the amphilphilic drug promethazine hydrochloride (PMT). A number of compounds raised the cloud point of the drug. These excipients can be classified as ionic and nonionic cloud-point boosters (CPBs). The nonionic CPBs include high molecular weight poly(ethylene glycols), poly(oxyethylene cetyl ethers), whereas ionic CPBs are cetylpyridinium chloride (CPC), cetylpyridinium bromide (CPB), cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), dodecyltrimethylammonium bromide (DTAB), 14-s-14 (s = 4, 5, 6), and 16-s-16 (s = 4, 6). The cloud-point suppressers include saccharides (sugars), amino acids, and alcohols. The extent of cloud-point (TCP) variation by different excipients is different (dependent on the nature and structure). The thermodynamic parameters are evaluated: whereas ΔGc° is found to be negative, ΔHc° and TΔSc° values are negative as well as positive (depending upon the type and nature of the additive).
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In this work, we developed a simple and selective method for separation and spectrophotometric determination of trace amounts of cetylpyridinium chloride (CPC) in pharmaceutical products using cloud point extraction (CPE) technique. The method is based on cloud point extraction of the CPC in alkali conditions using of nonionic surfactant Triton X-114. Under optimal conditions, the calibration graph was linear in the range of 0.50-30 μg/ mL of CPC with r=0.9993 (n=10). Average recoveries for spiked samples were determined to be between 95-104%. The relative standard deviation (RSD) for 5.0 μg/mL of CPC was 1.86 % (n=10). Also, the use of micellar extraction for extracting CPC was enhanced the molar absorptivity (ε) from 1.83×10(3) L/mol.cm in aqueous solution to 1.539×10(4) L/mol.cm in surfactant-rich phase. The proposed method was applied for the determination of CPC in a commercial mouth washer product.
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Abstract 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. Keywords: Speciation of chromiumcloud point extractionthenoyltrifluoracetoneETV‐ICP‐OESwater This project received financial support from the National Science Foundation of China.
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Cetylpyridinium chloride
Barium
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Barium chloride
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