不同基体改进剂对于火焰原子吸收法测定天然矿泉水中钙的影响

Effect of different matrix modifiers on determination of calcium in natural mineral water by flame atomic absorption spectrometry

目的确定火焰原子吸收法测定天然矿泉水中钙含量时的最优基体改进剂。方法将水样酸化处理后导入火焰,使水中钙原子化,选择测定波长为422.7 nm测定吸光度,绘制标准曲线。再取水样分别加入不同浓度梯度的磷酸二氢铵、硝酸铵、镧溶液、柠檬酸、EDTA-2Na和钯溶液作为基体改进剂,使用标准曲线法测定其中的钙含量,将结果进行对比。结果上述基体改进剂中,磷酸二氢铵与硝酸铵对钙的基体挥发性有负作用;柠檬酸与EDTA随着浓度梯度变化使钙浓度测定值浮动较大,结果很不稳定;使用钯溶液作为基体改进剂时,钙的测定浓度最接近真值。在使用40μg/L的钯溶液时,检出限为0.1 mg/L,加标回收率为98%~102.5%,RSD为1.27%。结论在样品中干扰过大的情况下,选用40μg/L的钯溶液为测定天然矿泉水中钙含量的最优基体改进剂。

Objective To determine the optimal matrix modifiers for determination of calcium content in natural mineral water by flame atomic absorption spectrometry. Methods After the water sample acidification was treated, the flame was imported and the water was atomized. The absorbance was determined by the determination of 422.7 nm, and the standard curve was drawn. In addition, the water samples were added to the different concentration gradients of ammonium dihydrogen phosphate, ammonium nitrate, lanthanum oxide solution, citric acid, EDTA-2Na and palladium solution as matrix modifiers, the standard curve method was developed for the determination of the calcium content, and the results were compared. Results Among the above matrix modifiers, ammonium dihydrogen phosphate and ammonium nitrate had a negative effect on the volatilization of calcium. The values of calcium concentration changed with the concentration gradients of citric acid and EDTA, which was very unstable. When the palladium solution was used as the matrix modifier, the concentration of calcium was closest to the true value. When using 40 μg/L palladium solution, the limit of detection was 0.1 mg/L, and the recoveries were 98%-102.5%, with the relative standard deviations of 1.27%. Conclusion In the case of excessive interference in the sample, the 40 mu g/L palladium solution is selected as the optimal matrix modifier for determination of calcium content in natural mineral water.