食用盐中铅含量分析方法的研究

Research on method of determination content of lead in edible salt

食用盐中含有大量的氯化钠,采用火焰原子吸收光谱法直接测定铅含量,其基质组分严重影响测定结果的准确度。本方法在pH为8～9时,用DDTC定量络合铅,经MIBK萃取与基体分离消除干扰后,再用硝酸反萃取,火焰原子吸收光谱法定量测定铅含量。样品中少量的钙、镁、铁、铝等干扰离子用柠檬酸铵加以掩蔽。通过实验比较,选择硝酸作为反萃取剂,1.6mol/L硝酸作为反萃取的适宜酸度。在此条件下,铅标准系列萃取-反萃取后测定值与直接测定值基本吻合,方法的特征浓度为0.20mg/L,检出限为0.01mg/L,样品的相对标准偏差为1.02%～3.22%,加标回收率为91.1%～98.4%。结果表明甲基异丁基甲酮(MI-BK)萃取-硝酸反萃取-火焰原子吸收光谱法可完全满足测定食用盐铅含量的要求。

Sodium chloride is the main substance in edible salt.However,sodium cation seriously affect the accuracy of the determination of the lead content by flame atomic absorption spectrometry（FAAS）.A method for the quantitative determination of lead was studied with DDTC lead complex at pH 8～9.The complex was extracted by MIBK and then separated by anti-extracting with nitric acid;Ammonium citrate was used to mask Ca,Mg,Fe,Al interfering.In this condition,the detecting value of standard series lead of extracted and anti-extracted was consisted with the value of direct detecting.The sensitivity of the method was 0.20mg/L,and detection limit was 0.01mg/L.The relative standard deviation was 1.02%～3.22%,and recovery rate was 91.1%～98.4%.Results showed that the method with MIBK extraction anti-extraction with the nitric acid and detected by flame atomic absorption spectrometry can be used in the lead determination in edible salt.