On-line speciation of mercury and methylmercury by cold vapour atomic absorption spectrometry using selective solid phase extraction

Abstract

A novel non-chromatographic on-line cold vapour atomic absorption spectrometric (CV-AAS) method for sequential mercury speciation at the ng l⁻¹ level was developed based on the selective retention of inorganic mercury on polytetrafluoro ethylene (PTFE) using a dual manifold. A column packed with PTFE turnings was used for inorganic mercury separation from the sample solution via the efficient retention on the sorbent material of the pyrrolidine dithiocarbamate complex Hg(PDC)₂. On the other hand, the PDC complex of methylmercury (CH₃HgPDC) is barely adsorbed, thus facilitating its direct determination after reduction by NaBH₄ and subsequent on-line thermal dissociation of the resulting hydride. Inorganic mercury in the presence of methylmercury species is determined in a parallel manifold due to the fact that the later one cannot be reduced by SnCl₂. The recovery of the proposed method was evaluated for drinking water, sea-water and urine samples.