Simultaneous determination of inorganic arsenic, antimony, selenium and tellurium by ICP-MS in environmental waters using SPE preconcentration on modified silica

This paper deals with a simplified multi-element profiling of inorganic arsenic, antimony, selenium and tellurium in the form of As-75, Se-82, Sb-121 and Te-125 by ICP-MS for amounts less than 10 mu g L-1. Internal standards such as Ge-72 and Bi-209 were successfully used for the suppression of both influence of macro elements Na+, K+, Ca2+, Mg2+ or Al3+, and interference of limited concentrations of heavy metal ions. Modified silica sorbents Separon (TM) SGX C18, C8, CN, NH2, RPS and Phenyl were tested for the preconcentration of As, Sb, Se and Te (0.25-5 mu g L-1) in the form of ion associates with cationic surfactants from 50-250 mL sample volume. 1-etoxycarbonyl-pentadecyltrimethylammonium bromide (Septonex (R), 0.005 mol L-1) was suitable for this purpose in the presence of 4-(2-pyridylazo) resorcinol, 2-pyrrolidinecarbodithioate and 8-hydroxyquinoline-5-sulphonic acid. The quantitative retention occurred at pH 7 +/- 0.2 and the mixture of acetone with ethanol in ratio 1 : 1 in the presence of 0.1 mol L-1 HCl was used for the quantitative elution. Organic solvents and the excess of acid were removed by evaporation prior to the determination by ICP-MS. The determination of the above trace metalloids in various kinds of water with enrichment factor till 50 times on silica Separon (TM) SGX C18 and the above reagents were compared with the standard addition method.