IMPROVEMENT IN DETERMINATION OF METHYLMERCURY IN SEDIMENTS BY HEADSPACE TRAP GAS CHROMATOGRAPHY AND ATOMIC FLUORESCENCE SPECTROMETRY AFTER ORGANIC EXTRACTION AND AQUEOUS PHASE ETHYLATION

摘要

An automated method for determination of methylmercury in sediments was developed using headspace coupled to gas chromatography with atomic fluorescence spectrometry detection and aqueous phase ethylation. The method avoids the problems associated with purge and trap techniques. The volume of ethylating agent was optimized and headspace only or headspace trap modes were evaluated. The results showed that the latter mode provided better performance for methylmercury determination than the former. An organic extraction of methylmercury from sediment samples was used involving the use of copper(II) sulfate, potassium bromide, and sulfuric acid. The method was verified by analysis of sediment reference materials (IAEA-405; IAEA-433) and the results were in good agreement with certified values. Due to the low detection limit, the method is appropriate for analysis of contaminated and uncontaminated sediment samples at ultratrace levels.