铬(Ⅲ)-硫氰酸钾-亚甲基蓝缔合体系褪色光度法测定痕量铬(Ⅲ)  

Photometric Determination of Trace Amount of Cr(Ⅲ) Based on the Colour Fading of the Association System of Cr(Ⅲ) Potassium Thiocyanate-Methylene Blue

作　　者：李人宇[1] 吴俊杰[1] 李咏梅[2] 

机构地区：[1]连云港师范高等专科学校,连云港222006 [2]淮海工学院化学工程学院,连云港222005

出　　处：《理化检验（化学分册）》2011年第6期695-697,共3页Physical Testing and Chemical Analysis(Part B:Chemical Analysis)

基　　金：连云港市科技项目(SH 0816);江苏省海洋资源开发研究院科技开放基金项目(JSIMR 09C08)资助

摘　　要：在pH 5.7的乙酸-乙酸钠缓冲溶液中,铬(Ⅲ)与硫氰酸钾和亚甲基蓝(MB)反应生成稳定的离子缔合物[MB]_3[Cr(SCN)_6],使MB褪色,据此建立了褪色光度法测定铬(Ⅲ)含量的方法。最大吸收波长为664 nm,铬(Ⅲ)质量浓度在0.006～0.30 mg·L^(-1)范围内与吸光度减小值呈线性关系,表观摩尔吸光率为1.04×10~5L·mol^(-1)·cm^(-1),检出限(3s/k)为5.4μg·L^(-1)。方法用于测定电镀废水中铬(Ⅲ),测得其加标回收率的平均值为98.1%;测定值的相对标准偏差均小于2%。In acetate buffer of pH 5.7, Cr（ Ⅲ ） reacts with potassium thiocyanate and methylene blue （MB） to form a stable ion-association complex of FMB23 ECr（SCN）6 1, leading to colour fading of methylene blue as measured at its absorption maximum of 664 nm. Linear relationship between values of decreasin absorbance and concentration of Cr（Ⅲ） was obtained in the range of 0. 006-0. 30 mg . L^-1 Detection limit （3s/k） found was 5.4 μg . L -1. Apparent molar absorptivity was found to be 1.04×105 L . mol .cm- 1. The proposed method was applied to the determination of Cr（Ⅲ） in electroplating waste water samples, giving values of average recovery of 98. 1% and RSD＇s （n=5） less than 2%.

关 键 词：褪色光度法 铬(Ⅲ) 硫氰酸钾 亚甲基蓝 离子缔合物 

分 类 号：O657.32[理学—分析化学]