Modification of Method of Sample Pretreatment in the Determination of Lead and Cadmium in Soil

As a modification for the method given in GB/T 17140-1997,the pretreatment of soil sample was improved by digesting in an acid mixture of HNO3+H2O2+HF (prepared in the ratio of 4+2+1) and heating in a microwave assisted digestor under specified parameters.The sample solution was evaporated to syrupy consistency and taken up with hydrochloric acid.Lead and cadmium ion in HCl solution were then extracted into 4-methyl-pentanone-2 (MIBK) as their iodide anionic complexes,and determined in MIBK-phase by FAAS.As proved by experimental data,the modified method showed its special features not only in precision and accuracy,but also rapid and convenient in operation.Values of RSD′s (n=10) obtained were less than 5% for both element,and recovery were 99.2% for lead(Ⅱ) and 96.4% for cadmium.