锌Ⅱ-硫氰酸钾-中性红体系双波长光度法测定痕量锌

Double-wavelength spectrophotometric determination of trace zinc with ZnⅡ-potassium thiocyanate-neutral red system

建立了测定痕量锌的双波长光度法。在阿拉伯树胶存在下和pH 5.7 HAc-NaAc缓冲溶液中,ZnⅡ与硫氰酸钾、中性红（NR）反应生成稳定的离子缔合物[NR]4[ZnⅡSCN）6],使NR褪色,在462 nm波长处出现正吸收峰,在574 nm处出现负吸收峰,实验选定测定波长为462 nm,参比波长为574 nm。表观摩尔吸光系数为5.66×104L.mol-1.cm-1,线性范围为0~1.0μg/mL,检出限为10.91μg/L。方法用于测定河水中锌,相对标准偏差分别为1.7%和1.6%（n=5）,样品加标回收率分别为99%和103%,测定结果与双硫腙光度法一致。

A new method was developed for determination of trace zinc by double-wavelength spectrophotometry.In the presence of arabic gum,Zn reacts with potassium thiocyanate and neutral red（NR）,forming a stable ion-association complex 4[Zn（SCN）6] in HAc-NaAc buffer solution at pH 5.7,which leads to the fading of NR.As a result,there were a positive absorption peak at 462 nm and a negative absorption peak at 574 nm.The apparent molar absorption coefficient was 5.66×104 L·mol-1·cm-1.The linear range of the determination was 0-1.0 μg/mL,and the limit of detection for zinc was 10.91 μg/L.The method has been applied to the determination of zinc in river water,with the RSDs of 1.7 % and 1.6 %（n= 5） and the recoveries of 99 % and 103 %,respectively.The results agreed well with those obtained by spectrophotometry with dithizone.