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

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.