火焰原子吸收分光光度法测定土壤中镍含量的不确定度评定

Uncertainty evaluation for determination of Ni in soil by flame atomic absorption spectrometry

目的评定火焰原子吸收法测定土壤中镍含量的不确定度。方法对种植基地土壤进行消解后定容,参照GB/T 17139-1997,采用火焰原子吸收分光光度法测定土壤中镍含量。通过对镍含量计算公式的分析,对试样水分、样品称量、消解液定容体积、标准溶液的配制、标准曲线的拟合等各个影响因素的不确定度分量进行计算及评估,计算合成的不确定度,并且通过调整标准曲线范围来降低结果的不确定度。结果当标准曲线浓度由0~3.0μg/mL调整为0~1.0μg/mL时,当土壤中镍含量为43.5 mg/kg时,扩展不确定度从5.0 mg/kg降到了1.2 mg/kg(k=2)。结论样品溶液质量浓度引入的不确定度是土壤中镍含量测定的测量不确定度的主要因素,其中标准曲线引入的不确定度贡献最大,可以通过调整标准曲线浓度范围,从而有效降低不确定度,对准确测量土壤中镍含量具有一定的意义。

Objective To evaluate the uncertainty for the determination of Ni content in soil by flame atomic absorption spectrometry.Methods The soil was firstly diluted with constant volume after digestion,then the Ni content was determined with flame atomic absorption spectrophotometry according to the standard of GB/T 17139-1997.Finally,by the analysis of the equation of Ni content,the uncertainty components of various influencing factors such as sample moisture,sample weighing,sample constant volume after digestion,standard solution and fitting of standard curve were calculated and evaluated to calculate the uncertainty of synthesis.Also,the concentration range of the standard curve was adjusted to reduce the uncertainty of the testing results.Results The experimental results showed that when the content of Ni in the soil was 43.5 mg/kg,the extended uncertainty was reduced from 5.0 mg/kg to 1.2 mg/kg(k=2)as the range of the standard curve turned to 0-1.0μg/mL from 0-3.0μg/mL.Conclusion The uncertainty of mass concentration is the main factor that influences the uncertainty of Ni content testing,especially the uncertainty of standard curve.The uncertainty of Ni content testing would be reduced by adjusting the range of standard curve,which is of certain significance for the accurate measurement of Ni content in soil.