在线富集—光纤传感分光光度法检测土壤中六价铬

Determination of hexavalent chromium in soil by on-line preconcentration-fiber optic spectrometry

目的建立一种在线富集—光纤传感分光光度法测定土壤中六价铬含量。方法在碱性条件下,硝酸铈为沉淀剂、用聚四氟乙烯滤膜管对六价铬进行在线富集、以HNO为洗脱剂、二苯基碳酰二肼为显色剂,使用自制流通池与光纤光谱仪连接构成的流动注射分析系统对土壤中六价铬进行含量测定。考察了沉淀剂、洗脱剂、流速、富集时间、显色剂浓度和反应管长度的影响。结果六价铬的浓度线性回归方程为:y=0.0101x-0.0002,在最佳实验条件下测定六价铬的线性范围为5.0~25.0μg/L,六价铬摩尔浓度与吸光度成良好的线性关系,相关系数r=0.9995,检出限为0.4 mg/kg,相对标准偏差为0.69%,加标回收率为95.24%~104.59%。结论本研究测定土壤中六价铬的方法简单,样品通过在线富集排除干扰因素的影响,无需消化处理,可以用于直接测定土壤中六价铬的含量及评价。

Objective To establish a method of an online preconcentration-fiber optical sensing spectrophotometry for the determination of the content of hexavalent chromium[Cr(VI)]in soil.Methods A flow injection analysis system comprising a self-made flow cell and a fiber optical spectrometer was used to determine the content of Cr(VI)in soil samples,after on-line Cr(VI)preconcentration through a polytetrafluoroethylene filter under alkaline conditions,with cerium nitrate as the precipitant,nitric acid as the eluent,and 1,5-diphenylcarbazide as the chromogenic reagent.The effects of the precipitant,eluent,flow rate,preconcentration time,chromogenic reagent concentration and reaction tube length were examined.Results The linear regression equation of Cr(VI)concentrations was:y=0.0101x-0.0002.The linear range of Cr(VI)determined under the optimal experimental conditions was 5.0 to 25.0μg/L.The molar concentration of Cr(VI)and the absorbance showed a good linear relationship,with a correlation coefficient of 0.9995.The detection limit was 0.4 mg/kg,with relative standard deviation 0.69%,and recovery 95.24-104.59%.Conclusion The method established in this study is a simple and direct approach to measuring the content of Cr(VI)in soil through on-line sample preconcentration,avoiding the influence of confounding factors caused by pre-processing.