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    聚乙烯醇-水-丙酮体系分离富集-PAR光度法测定环境水样中痕量镉

    PAR Photometric Determination of Trace Amounts of Cadmium After Separation and Enrichment from PVA-H2O-Acetone System

    • 摘要: 利用聚乙烯醇(PVA)-镉络合物在水和丙酮中溶解度的差异,提出了水溶性聚乙烯醇丙酮体系分离富集痕量镉的方法.在pH 3~10的溶液中,Cd2+与PVA生成水溶性络合物,当加入足够量的丙酮(≥25 mL)及饱和氯化钾(1.0 mL)溶液作盐析剂时,此络合物沉淀析出.用倾倒法将液固分离后,用少量水溶解沉淀,以PAR作显色剂用光度测定其含镉量.线性范围为5~2 000 μg·L-1,检出限(3s/b)为2 μg·L-1.该方法用于环境水样中镉的测定,所得结果与火焰原子吸收光谱法测得的结果相符.用标准加入法测得方法的回收率在96.3%~98.0%之间.对沉淀分离过程的机理也作了简要论述.

       

      Abstract: Based on the difference of solubility of the complex of Cd(Ⅱ) with polyvinylalcohol (PVA) in water and in acetone,a method for separation and enrichment of trace amounts of Cd2+-ion was proposed.In a solution of pH 3-10,a water soluble complex was formed between Cd2+-ion and PVA,which was insoluble in acetone and separated out upon addition of sufficient amount of acetone (≥25 mL).Saturated solution of KCl (1.0 mL) was added as salting-out agent in the precipitation.Precipitate of Cd2+-PVA was separated from the solution by decantation,dissolved in a small volume of water and determined photometrically with PAR as color reagent.Linear relationship between values of absorbance and concentration of Cd2+-ion was obtained in the range of 5-2 000 μg·L-1.Detection limit (3s/b) of the method found was 2 μg·L-1.In the determination of cadmium in water samples,the results found by this method were checked quite well with the results obtained by FAAS.Values of recovery obtained by standard addition method were in the range of 96.3%-98.0%.A brief discussion on the mechanism of the precipitation process was also given.

       

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