小型离子交换柱分离-电感耦合等离子体原子发射光谱法测定餐具用钢中镉

使用Strelow法测定不同浓度盐酸中铁和镉在DOWEX 1×X8阴离子交换树脂上的分配系数。结果显示,在1 mol/L盐酸中,铁(Ⅲ)的K_d值低于10 mL/g,不能吸附在树脂上;而镉(Ⅱ)的K_d值为2 281 mL/g,强吸附在树脂上,因此可以实现两者的有效分离。使用盐酸溶解餐具用钢样品,溶液通过装填了DOWEX 1×X8阴离子交换树脂的小型柱,铁(Ⅲ)可以顺利通过,而镉(Ⅱ)吸附在离子柱中,从而实现镉与铁的有效分离和富集。然后用1 mL 1.6 mol/L硝酸洗下吸附在柱子上的镉,收集的溶液使用电感耦合等离子体原子发射光谱法(ICP-AES)测定,从而建立了小型离子交换柱分离-电感耦合等离子体原子发射光谱法测定餐具用钢中微量镉的方法。镉的质量浓度在0.010～0.10 mg/L范围内与发射强度呈线性,校准曲线的线性相关系数为0.999 9。方法中镉的检出限为0.004 g/mL(相当于实际样品中镉的质量分数为0.04 μg/g)。按照实验方法测定餐具用钢样品中镉含量,结果的相对标准偏差(RSD,n=7)为5.8%～7.3%,加标回收率为90%～100%。

Determination of cadmium in steel for cutlery by inductively coupled plasma atomic emission spectrometry after separation with small ion exchange column

The distribution coefficient of iron and cadmium in hydrochloric acid with various concentrations on DOWEX 1×X8 anion exchange resin was determined by Strelow method. The results showed that the K_d value of iron (Ⅲ) in 1 mol/L hydrochloric acid was less than 10 mL/g, indicating that it could not be adsorbed on the resin. However, the K_d value of cadmium (Ⅱ) was 2 281 mL/g, indicating that it could be strongly adsorbed on the resin. Therefore, iron (Ⅲ) and cadmium (Ⅱ) could be effectively separated. The steel sample for cutlery was dissolved with hydrochloric acid,then the sample solution flowed through the small column which was packed with DOWEX 1×X8 anion exchange resin. The iron (Ⅲ) in solution could pass through the column, while cadmium (Ⅱ) would be adsorbed onto the column, realizing the effective separation and enrichment of cadmium and iron. Then, the cadmium (Ⅱ) on column was eluted with 1 mL of 1.6 mol/L nitric acid. The content of cadmium in collected solution was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).Consequently,the determination method of micro cadmium in steel for cutlery by ICP-AES after separation with small ion exchange column was established. The mass concentration of cadmium in range of 0.010-0.10 mg/L was linear to the emission intensity. The linear correlation coefficient of calibration curve was 0.999 9. The detection limit of cadmium was 0.004 g/mL (which was equivalent to the mass fraction of 0.04 μg/g of cadmium in actual sample). The content of cadmium in steel for cutlery was determined according to the experimental method. The relative standard deviation (RSD, n=7) was 5.8%-7.3%. The recoveries were between 90% and 100%.