Hg^(2+)-碘化物-吖啶橙-聚乙烯醇缔合体系褪色光度法测定痕量汞

Fading spectrophotometric determination of trace mercury with Hg^(2+)-iodide-acridine orange-polyvinyl alcohol association system

在pH3.6 NaAc-HAc缓冲溶液中,聚乙烯醇存在下,Hg2+与过量的I-和吖啶橙(AO)反应生成稳定的离子缔合物[AO]2[HgI4],使AO褪色,据此建立了褪色光度法测定痕量汞的新方法。最大褪色波长为490 nm,体系的褪色程度与Hg2+浓度在0～0.8μg/mL范围内呈线性关系,表观摩尔吸光系数为9.17×104L.mol-1.cm-1,检出限为20.7μg/L。采用巯基棉分离富集,测定河水中汞,相对标准偏差为1.4%～2.7%(n=5),回收率在98%～101%之间。

In NaAc-HAc buffer solution at pH 3.6 and in the presence of polyvinyl alcohol,Hg^2＋ reacts with excess I-and acridine orange（AO） forming a stable ion-association complex 2,which makes AO fade.Accordingly,a new fading spectrophotometric method is developed for determining trace mercury.The maximum fading wavelength is at 490 nm.The fading grade is linear with the concentration of Hg^2＋ in the range of 0-0.8 μg/mL with the apparent molar Absorption coefficient of 9.17×10^4 L·mol^-1·cm^-1 and the detection limit of 20.7 μg/L.The method has been applied to determine mercury in river samples after enrichment and separation with thiol cotton fiber.The relative standard deviation is 1.4%-2.7 %（n=5） and recoveries are from 98 % to 101 %.