FAAS Determination of Calcium and Magnesium in High-purity Lithium Salts with Pre-concentration on Micro-column

Traces of Ca2+ and Mg2+ testing solution of pH 8 were separated and enriched by passing through the micro-column packed with IRC 747 resin,at the flow-rate of 2.0 mL·min-1. After removing the Li+ from the column by elution with 0.5 mol·L-1 HOAc and H2O,Ca2+ and Mg2+ were desorbed from the column with 1.0 mol·L-1 HCl as eluant at the flow-rate of 2.5 mL·min-1. The eluate was collected and used for FAAS determination. Solutions of citric acid and La(Ⅲ) salt were used as releasing agent for Ca2+,and mixed solution of La(Ⅲ) and Sr(Ⅲ) salts was used as releasing agent for Mg2+. In addition,the sensitivity of determination of Ca2+ and Mg2+ was raised by the addition of CTMAB solution,and the magnitude of enhancement of sensitivity was attained to values of 25% for Ca2+ and 22% for Mg2+. In analyzing samples of high-purity lithium carbonate and lithium chloride by this method,results of Ca2+ and Mg2+ contents found were in consistency with the results obtained by ICP-AES,with values of RSD′s (n=8) less than 3%,the recovery ranged from 99.1% to 100.9%.