石墨炉原子吸收法测定土壤中铅、镉的方法探讨

Exploration of the graphite furnace atomic absorption method for the determination of plumbum and cadmium content in soil

目的建立土壤中铅、镉的电热板湿法消解——石墨炉原子吸收分光光度法。方法用电热板湿法消解对赣榆区5个乡镇土壤进行消化,石墨炉原子化器对所含的铅、镉离子在石墨管经原子化高温蒸发分解为原子态蒸气,由氩气带入原子吸收光谱仪中进行检测,同时研究仪器、基体改进剂磷酸氢二铵浓度及用量等分析条件对测定铅、镉的影响。结果铅含量0~600.0μg/L、镉含量0~6.0μg/L浓度范围内线性关系良好(r=0.9995),检出限铅5.700μg/L、镉0.024μg/L;取3种不同浓度的土壤标准物质连续测定6次,相对标准偏差铅为9.66%、9.73%、4.53%,镉为4.98%、8.01%、6.34%;对3份本地的土壤中检测其相对标准偏差铅3.68%~6.82%、镉4.35%~9.23%,加标回收率铅86.00%~101.59%、镉88.70%~100.70%。抽查土壤结果显示,赣榆区土壤检测结果符合《土壤环境质量标准》(GB 15618—1995)中的二级标准要求。结论电热板湿法消解能满足土壤中铅、镉的监测要求,结果较为满意,便于基层实验室推广使用。

Objective To establish the electric heating plate wet digestion of plumbum(Pb)and cadmium(Cd)in soil-graphite furnace atomic absorption spectrophotometry.Methods The soil collected from 5 townships in Ganyu District was digested with electric heating plate wet digestion.The Pb and Cd ions contained in the graphite furnace atomizer were decomposed into atomic vapor by atomization and high temperature evaporation in the graphite tube,and then were brought into the atomic absorption spectrometer by argon for detection.At the same time,the influence of analytical conditions such as the instrument,the concentration and dosage of and matrix modifier diammonium hydrogen phosphate on the determination of Pb and Cd ions was also studied.Results A good linear relationship(r=0.9995)was exhibited over a concentration range of 0-600.0μg/L for the Pb content and 0-6.0μg/L for the Cd content.The detection limit was 5.700μg/L for Pb and 0.024μg/L for Cd.The relative standard deviations were 9.66%,9.73%,4.53%for Pb,and 4.98%,8.01%,6.34%for Cd after six consecutive determinations of three different concentrations of soil standards.In the three local soils,the relative standard deviations were 3.68%-6.82%for Pb,4.35%-9.23%for Cd,and the recovery rates were 86.00%-101.50%for Pb and 88.70%-100.70%for Cd,respectively.The results of soil sampling showed that the soil testing results in Ganyu District were in accordance with the secondary standard in The Soil Environmental Quality Standard(GB 15618—1995).Conclusion The electric heating plate wet digestion method can meet the monitoring requirements of Pb and Cd ions in soil,and the results are relatively satisfactory,which is convenient for the promotion and use of basic laboratories.