采用ICP-AES法同时测定工业铬酸钠溶液中微量Al, Ca, Fe, Mg, Si杂质元素。针对测定过程中存在的基体干扰、谱线干扰等问题, 通过实验确定了铬酸钠中微量的Al, Ca, Fe, Mg, Si的分析测试谱线: Al 167.079 nm, Ca 393.366 nm, Fe 259.940 nm, Mg 279.533 nm, Si 251.61 nm。实验用优级纯HCl将待测溶液调为酸性, 消除工业铬酸钠溶液酸度不稳定引起的测定误差, 采用标准加入法消除基体干扰, 探讨了Al, Ca, Fe, Mg, Si等五种微量组分检测方法标准曲线线性相关性、检出限、精密度以及回收率等分析指标, 详细研究了在选定分析谱线下, 标准加入法对铬酸钠溶液中Al, Ca, Fe, Mg, Si等微量杂质含量测定结果的准确性的影响。结果表明标准曲线呈线性关系(R2=0.998 8～0.999 6之间), 五种元素检出限在(0.013 4～0.028 0)mg·L-1之间, 11次测量标准偏差小于5.86%, 回收率在97.30%～107.50%之间。实验建立的分析方法的检出限、精密度、准确度均能满足分析测试要求;方法实用性强, 已经成功用于离子膜电解法中铬酸钠原料液微量离子检测;利用铬酸钠、重铬酸钠和重铬酸酐与溶液酸度的关系, 实验建立的分析方法还可拓展于重铬酸钠及铬酐甚至其他六价铬产品中Al, Ca, Fe, Mg, Si杂质离子的检测, 同时也可以扩展到上述样品中其他杂质元素的测定。

Coupled plasma atomic emission spectrometry (ICP-AES) was used to determine the trace impurities of Ca, Mg, Al, Fe and Si in industrial sodium chromate. Wavelengths of 167.079, 393.366, 259.940, 279.533 and 251.611 nm were selected as analytical lines for the determination of Al, Ca, Fe, Mg and Si, respectively. The analytical errors can be eliminated by adjusting the determined solution with high pure hydrochloric acid. Standard addition method was used to eliminate matrix effects. The linear correlation, detection limit, precision and recovery for the concerned trace impurities have been examined. The effect of standard addition method on the accuracy for the determination under the selected analytical lines has been studied in detail. The results show that the linear correlations of standard curves were very good (R2=0.998 8 to 0.999 6) under the determined conditions. Detection limits of these trace impurities were in the range of 0.013 4 to 0.028 0 mg·L-1. Sample recoveries were within 97.30% to 107.50%, and relative standard deviations were lower than 5.86% for eleven repeated determinations. The detection limits and accuracies established by the experiment can meet the analytical requirements and the analytic procedure was used to determine trace impurities in sodium chromate by ion membrane electrolysis technique successfully. Due to sodium chromate can be changed into sodium dichromate and chromic acid by adding acids, the established method can be further used to monitor trace impurities in these compounds or other hexavalent chromium compounds.