活性氧化铝富集火焰原子吸收法测定铬（Ⅲ）和铬（Ⅵ）

Determination of Chromium(Ⅲ)and Chromium(Ⅵ)by Flame AAS with Preconcentration on Activated Alumina Column

研究了内装活性氧化铝的微型柱流动注射富集分离火焰原子吸收光谱法（Ｆｌ－ＦＡＡＳ）测定水体中μｇ／Ｌ级的Ｃｒ（Ⅲ）、Ｃｒ（Ⅵ）。用０．２ｍｏｌ／Ｌ氨水将活性氧化铝转为碱式以吸附Ｃｒ（Ⅲ），１ｍｏｌ／Ｌ硝酸洗脱；用０．０１ｍｏｌ／Ｌ的硝酸将活性氧化铝转为酸式以吸附Ｃｒ（Ⅵ），０．２ｍｏｌ／Ｌ的氨水洗脱，洗脱液直接送到喷雾器中。进样３０ｓ，浓度富集２５倍。两种价态离子的校正曲线浓度范围在１～５０μｇ／Ｌ之间，检测限分别为０．６和０．７μｇ／Ｌ，样品分析速率为６０样／ｈ。研究了共存离子的干扰情况，实际水样中的加标回收率在８５％～１０５％之间。

A flame AAS method for trace Cr(Ⅲ)and Cr(Ⅵ)determination in natural water(μg/L level)is described,using flow injection preconcentration and separation on an activated alumina microcolumn.The activated alumina was transformed into the basic form with 0. 2 mol/L ammonia solution.Cr(Ⅲ) was absorbed on the basic activated alumina,and was then eluted with 1 mol/L nitric acid. For the preconcentration of Cr(Ⅵ) ,the activated alumina was transformed into the acidic form with 0. 01 mol/L nitric acid. The absorbed Cr(Ⅵ)was then eluted with 0. 2 mol/L ammonia solution. The eluants were fed directly into the nebulizer. An enrichment of 25 times was obtained under a sample loading of 30 seconds. The linear ranges of calibration curves for both species were 1～50 μg/L,while the detection limits for Cr(Ⅲ)and Cr(Ⅵ) were found to be 0. 6 and 0.7 μg/L,respectively. Analyses can be performed at a frequency of 60 samples/h. The interference of co-existing ions has been studied. The chromium recovery from natural water samples was 85%～105% .