流动注射分光光度法测定微量硫氰酸根

Flow Injection -Spectrophotometric Determination of Micro Amounts of Thiocyanate

基于３，５－Ｂｒ２－ＰＡＤＡＰ、硫氰酸根分别与重铬酸根、铈（Ⅳ）在硫酸介质中反应生成不稳定的蓝色产物，建立了两种测定微量硫氰酸根的流动注射分光光度新方法。在前一方法中，硫氰酸根含量在０．８０－７．２０ｍｇ／Ｌ范围内可定量测定，检出限为０．２７ｍｇ／Ｌ；在后一方法中，硫氰酸根含量在０．８０－６．４０ ｍｇ／Ｌ范围内呈线性，检出限为 ０．３０ ｍｇ／Ｌ。当进样体积为 １００μＬ时，进样频率为６０次／ｈ。所建立的两种方法灵敏度高、选择性好、重现性好、简便快速，用于唾液和废水中硫氰酸根的测定，结果令人满意。

Two flow injection methods have been developed for the spectrophotometric determination of micro amounts of thiocyanate, based on the reaction of 2-(3, 5 - dibromo-2- pyridylazo) -5 - diethylamino- phenol(3,5-Br2 - PADAP ) - thiocyanate- dichromate system in acidic medium (method A ), and the reaction of 3, 5 - Br2 - PADAP- thiocyanate- Ceritun (IV ) system in ac idle medium (method B ). Both reactions pro duce unstable violet products with maximum absorption at 602 nm. In system A, the calibration curve is linear in the range from 0. 80 to 7 .20 mg/L of SCN- and the detection limit is 0.27 mg/L. In system B, the calibration curve is linear in the range from 0. 80 to 6. 40 mg/L of SCN- and the detection limit is 0.30 mg/L. With a sample solution of 100 uL being injected, the sampling frequency is 60/h for A or B mehtod. Both methods have been applied to determine thiocyanate in waste water, saliva of non-smokers and smokers with satisfactory results.