交联羧甲基淀粉预富集-悬浮体进样-石墨炉原子吸收法测定水样中铬(Ⅲ)和铬(Ⅵ)

Crosslinked Carboxymethyl Starch Based Solid Phase Extraction Combined with Direct Slurry Sampling Graphite Furnace Atomic Absorption Spectrometry for Determination of Trace Cr(Ⅲ) and Cr(Ⅵ)in Water

以交联羧甲基淀粉(CCMS)为吸附剂,悬浮体进样-石墨炉原子吸收法(GFAAS)测定环境水样中Cr(Ⅲ)和Cr(Ⅵ)形态。研究了溶液pH值、吸附时间、溶液体积、共存离子等对CCMS吸附Cr(Ⅲ)和Cr(Ⅵ)的影响。结果表明:在pH=6.0时,吸附15 min,CCMS可以选择性地吸附Cr(Ⅲ),对Cr(Ⅵ)不吸附,从而实现Cr(Ⅲ)和Cr(Ⅵ)的分离。将吸附Cr?的CCMS加0.1%的琼脂制成悬浮体直接进石墨炉检测,用1 mL 1%盐酸羟胺将Cr(Ⅲ)还原成Cr(Ⅵ),测总铬。方法对Cr(Ⅲ)的检出限为0.044μg/L,相对标准偏差(RSD)为10.4%(初始浓度CCr(Ⅲ)=1.0μg/L,n=11),富集倍数为50倍。将本方法应用于环境标准样品的测定,测得结果与标准值相符。

A new method of solid phase extraction（SPE）,using crosslinked carboxymethyl starch（CCMS） as adsorbent,combined with direct slurry sampling graphite furnace atomic absorption spectrometry（ss-GFAAS） has been developed for the speciation of trace Cr（Ⅲ） and Cr（Ⅵ） in environmental water samples.Various influencing factors on the separation and preconcentration of Cr（Ⅲ） and Cr（Ⅵ）,such as the acidity of the aqueous solution,sample volume,adsorption time and effects of other ions,have been investigated systematically.Cr（Ⅲ） could be selectively retained by CCMS at pH 6.0 within 15 min,then the retained Cr（Ⅵ） on the CCMS was separated and the slurry of the precipitate prepared in 0.1% agar suspension was directly injected into the graphite furnace for the determination of Cr（Ⅲ）.Total chromium was determined after the reduction of Cr（Ⅲ） to Cr（Ⅵ） by 1 mL 1% hydroxylamine hydrochloride,and Cr（Ⅲ） concentration was calculated by subtracting Cr（Ⅲ） from total chromium.The detection limit for Cr（Ⅲ） was 0.044 μg/L with an enrichment factor of 50,and the relative standard deviation（RSD） was 10.4%（cCr（Ⅲ） =1.0 μg/L,n=11）.The proposed method has been applied to the speciation of chromium in water samples with satisfactory results.To validate the method,the proposed method was also applied to the determination of Cr（Ⅲ） and Cr（Ⅵ） in environmental water reference materials and the results obtained were in good agreement with the certified value.