5＇－硝基水杨基荧光酮分光光度法测定微量铬（Ⅵ）的研究

Spectrophotometric Determination of Micro Amounts of Chromium(Ⅵ) with 2,6,7 Trihydroxy 9 (2’ hydroxy 5’ nitrophenyl)fluorone

本文研究了新显色剂５＇－硝基水杨基荧光酮（５＇－ＮＳＦ）在阳离子表面活性剂溴化十六烷基三甲铵（ＣＴＭＡＢ）存在下与铬（Ⅵ）的显色反应。在ｐＨ５．５～６．７的磷酸盐缓冲介质中，Ｃｒ（Ⅵ）与５＇－ＮＳＦ反应生成组成比为１＋４的水溶性和稳定性皆佳的紫色配合物，吸收峰波长λｍａｘ＝５８６ｎｍ，对比度△λ＝６３ｎｍ，表观摩尔吸光系数５８６＝１．７４×１０５Ｌ·ｍｏｌ－１·ｃｍ－１，桑德尔灵敏度是３．０×１０－４μｇ·ｃｍ－２，Ｃｒ（Ⅵ）浓度为０～０．２１μｇ／ｍＬ时服从比尔定律。采用阴离子交换树脂分离，能够消除许多金属离子的干扰。方法用于水样中微量总铬、Ｃｒ（Ⅵ）和Ｃｒ（Ⅲ）的测定。

The chromogenic reaction of chromium(Ⅵ)with a new reagent 2,6,7 trihydroxy 9 (2' hydroxy 5' nitrophenyl)fluorone(5' NSF)has been studied at pH 5.5～6.7 in the presence of hexadecyltrimethylammonium bromide.After the solution is heated for 15 min on a water bath at 60～65℃,a violet red complex is formed with a maximum absorption at 586 nm.Its apparent molar absorptivity is 1.74×10 5 L·mol -1 ·cm -1 ,while its Sandell sensitivity is 3.0×10 -4 μg·cm -2 .The molar ratio of chromium(Ⅵ)to 5' NSF in the complex was found to be 1+4.Beer's law is obeyed in the concentration range of 0～0.21μg/mL for chromium.The proposed procedure has been satisfactorily applied to the determination of micro amounts of chromium(Ⅵ)and total chromium in river water with prior separation on an anion exchanger column.