二苯硫腙-CCl_4-萃取-分光光度法连续测定水样中铜和铅

Successive Spectrophotometric Determination of Copper and Lead in Water Samples by Dithizone-CCl4 Extraction

应用二苯硫腙萃取分光光度法连续测定水样中铜(Ⅱ)和铅(Ⅱ)。在pH 3.8的乙酸盐缓冲介质中,用四氯化碳作溶剂萃取铜(Ⅱ)和二苯硫腙的络盐并在551 nm波长处测定溶液的吸光度。在萃取铜(Ⅱ)后的水相中加入pH 10的氨性缓冲溶液,并用1 mol.L-1NaOH溶液调节溶液的酸度为pH 9.2,仍用四氯化碳作溶剂萃取铅(Ⅱ)与二苯硫腙的络盐,在525 nm波长处测定其吸光度。测得铜(Ⅱ)及铅(Ⅱ)的二苯硫腙络盐在CCl4溶液中的摩尔吸光率依次为6.8×104及1.3×105L.mol-1.cm-1。应用此方法测定了一种水样中的铜(Ⅱ)和铅(Ⅱ),分析结果的RSD(n=6)值依次为3.0%及8.4%。

Dithizone extraction spectrophotometry was applied to the successive determination of Cu（Ⅱ） and Pb（Ⅱ） in water samples. Carbon tetrachloride （CCl4） was used as extraction solvent in both cases. The extraction of Cu（Ⅱ） dithizonate was carried out in an acetate buffer medium of pH 3. 8, and the absorbance of the complex in CCh was measured at the wavelength 551 nm. An ammoniacal buffer solution of pH 11 was added to the aqueous phase remained after extraction of Cu（Ⅱ）, and appropriate amount of 1 mol · L-1 NaOH solution was added to adjust the pH of the solution to pH 9. 2. Lead（Ⅱ） was then extracted as its dithizonate by CCh from the solution and its absorbance measured at the wavelength of 525 nm. Values of molar absorptivity of Cu-dithizonate and Pb- dithizonate inCCh were found to be （εCu） 6. 8× 10^4L ·mol^-1 · cm^-1 and （εPb） 1. 3× 10^5L ·mol· cm^-1 respectively. In the determination of Cu（Ⅱ） and Pb（Ⅱ） in a sample of tap water, values of RSD＇s （n=6） obtained were 3.0% and 8. 4% for Cu（Ⅱ） and Pb（Ⅱ） respectively.