石墨炉原子吸收光谱法测定食盐中镉的含量

Determination of Cd in Edible Salt by Graphite Furnace Atomic Absorption Spectrometry

提出了石墨炉原子吸收光谱法测定食盐中镉含量的方法。称取食盐样品0.5 g,用1%(体积分数,下同)硝酸溶液溶解并定容至50 mL,摇匀,配制成待测样品溶液。以1%硝酸溶液为溶剂,配制成含10 g·L^(-1)磷酸二氢铵和10 g·L^(-1)抗坏血酸的基体改进剂。测定时,采用自动进样器吸取1.0μL基体改进剂至20μL待测样品溶液中。优化后的石墨炉升温条件:干燥温度为120℃,灰化温度为350℃,原子化温度为700℃,净化温度为2 700℃。结果显示:镉的质量浓度在0.1~2.0μg·L^(-1)内与其对应的吸光度呈线性关系,检出限(3s/k)为0.001 mg·kg^(-1);对含不同质量分数镉的氯化钠加标溶液进行测定,测定值的相对标准偏差(n=6)均小于4.0%;对不同类型的食盐样品进行加标回收试验,镉回收率为92.0%~101%。

A method for the determination of Cd in edible salt by graphite furnace atomic absorption spectrometry was proposed.Edible salt sample(0.5 g)was dissolved and made its volume up to 50 mL with 1%(φ)nitric acid solution to prepare the test sample solution after shaking.1%(φ)nitric acid solution was used as solvent,the matrix modifier containing 10 g·L^(-1) ammonium dihydragen phosphate and 10 g·L^(-1) ascorbic acid was obtained.Matrix modifier(1.0μL)was absorbed into the test sample solution(20μL)by an automatic sampler.The optimized heating conditions of graphite furnace were as follows:the drying temperature of 120℃,the ashing temperature of 350℃,the atomization temperature of 700℃,and the purification temperature of 2700℃.As shown by the results,linear relationship between values of mass concentration of Cd and its absorbance was kept in the range of 0.1-2.0μg·L^(-1),with detection limits(3s/k)of 0.001 mg·kg^(-1).Spiked solutions of sodium chloride containing different mass fractions of Cd were determined,and RSDs(n=6)of the determined values were less than 4.0%.Test for recovery was made on different types of edible salt samples by standard addition method,giving results in the range of 92.0%^(-1)01%.