METHYLMERCURY DETERMINATION BY PURGE AND TRAP-GC-FTIR-AAS AFTER NABH4 DERIVATIZATION OF AN ENVIRONMENTAL THIOSULFATE EXTRACT

A method of detecting methylmercury species (MeHg) and dimethylmercury (DMM) has been studied. MeHg was transformed prior to its determination as methylmercury hydride (MMH) by use of NaBH4. The two volatile forms of organic mercury were detected by a purge and trap (PT) unit in-line with a gas chromatograph (GC) connected with a Fourier transform infrared spectrometer (FTIR) which was also in-line with an atomic absorption spectrometer (AAS). Environmental samples were analyzed by this technique. MeHg was detected in thiosulfate extracts of fish and sediment, and MeHg and DMM directly in water samples. Picogram levels of sensitivity were obtained, the limit of detection being 100 pg for MeHg and 50 pg for DMM. The calibration graph was linear for both compounds up to 10 ng as Hg.