Use of lanthanum hydroxide as a trapping agent to determine of hydrides by HG-ICP-OES

Abstract

The level of arsenic and antimony was determined in sea-water by axial ICP-OES with continuous hydride generation after performing pre-reduction with thiourea and carrying out a pre-concentration by co-precipitation with lanthanum in a PTFE knotted reactor (KR). Optimisation of the whole system was performed using experimental design and with on-line pre-concentration and ultimate hydride generation. Using a pre-concentration time of two minutes and consuming 16 mL of sample, the LOD and LOQ were 0.17 and 0.56 μg L⁻¹, respectively, for As, and 0.27 and 0.88 μg L⁻¹ for Sb. Pre-concentration was carried out off-line in the KR in order to decrease the LOD and LOQ to 0.031 and 0.10 μg L⁻¹ (As 188.979 nm) and 0.043 and 0.15 μg L⁻¹ (Sb 217.582 nm) (sample volume 83 mL). The method was precise, with RSDs (n = 11) of 5.7% for As and 9.4% for Sb. The method was accurate, with a recovery of 108.5% for As and 106.0% for Sb. Moreover, values of 3.0 ± 0.5 μg As L⁻¹ and 14.7 ± 1.5 μg Sb L⁻¹ were obtained for a reference material with certified content of 2.7 ± 1.0 μg As L⁻¹ and 13.7 ± 8.5 μg Sb L⁻¹. The method can be applied to element determination in unpolluted sea-water samples.