Studies On Morphological Analysis Of Chromium In Water Samples Based On Cloud Point Extraction-spectrum/chromatogram

Cloud point extraction(CPE)is kind of rapidly-developed environmental benign liquid-liquid extraction technique which is based on the property of solubility and cloud point phenomenon in aqueous solutions of surfactants,upon alteration of the experimental conditions such as pH value,ionic force,temperature of solution,which results in the extraction of hydrophobic complex from water phase when the measured material and complexing agent formed to complex.Cloud point extraction has the advantages of high extraction efficiency,easy and safe methodology for preconcentration and separation.It has been widely used in the trace or semi-trace substances before pre-treatment process.The low content of the trace element in the sample and the great difficult in the separation of different forms of the same element,which required the analytical technique that is highly sensitive and selective.Many methods applied to conduct the researches on the forms of the element have been used,But when the characteristics of several forms in the sample are similar,the direct determination will make them interfere with each other,which a separation before determination is required.A method determined by high pressure liquid chromatography and flame atomic absorption spectrometry coupling with the cloud point extraction as the preconcentration technology,and applied to determine the trace Cr element speciation in water samples.HPLC technology is widely used in the analysis of organic material owing to the separation and determination in HPLC technology.In this research HPLC technology has been proposed for speciation of chromium.Simultanous preconcentration and separation of the Cr(?)and Cr(?)in aqueous solutions were realized on CPE with ammonium pyrrolidine dithiocarbamate(APDC)as complexing agent and non-ionic surfactant Triton X-114 as cloud point extractant.Baseline separation of APDC chelates with Cr(?)and Cr(?)was achieved by a mixture of methanol-water as the mobile phase.The effects of experimental conditions were discussed.Under the optimum conditions,The enrichment factor for Cr(?)and Cr(?)was 15 and 17,respectively.With 0.96?g/L&1.92? g/L for the detection limits of Cr(?)&Cr(?).Then the method was applied to the speciation of Cr(?)and Cr(?)in tap water,river water samples.The complexing agent always contributes to different behavior when complexing with the same mental of different speciations in a range of medium pH,A large variances of difference speciations existed in the morphology and hydrolysis characteristic at different pH.In this research CPE technology has been proposed for separation of element speciation.The CPE technology was realized on the using of Sodium diethyldithiocarbamatre(DDTC)as complexing agent and non-ionic surfactant Triton X-114 as cloud point extractant.In this method,Cr(III)reacts with DDTC yielding a hydrophobic complex at pH=8.5,which then is entrapped in the surfactant-rich phase,whereas Cr(VI)remained in aqueous phase.Thus the separation of Cr(III)and Cr(VI)could be realized.Both Cr(III)and Cr(VI)could complex with DDTC yielding two hydrophobic complex when adjust the medium pH to 4.8,the analyte was extracted to the surfactant-rich phase with proper dilution before AAS.The effects of experimental conditions were discussed.Under the optimum conditions,The method was applied to the analysis of water samples,the result is consistent to the result of CPE-HPLC above-mentioned.