Determination of mercury in coal by non-oxidative pyrolysis and cold vapour atomic-fluorescence spectrometry

Abstract

Mercury was liberated from coal by non-oxidative pyrolysis at 800 °C with a nitrogen purge and collected in acidified potassium permanganate solution. Subsequent determination was by cold vapour atomic-fluorescence spectrometry using an argon-sheathed windowless cell. The mercury vapour was generated continuously by pumping tin(II) chloride and sample to a novel reduction cell. This continuous flow system offered excellent precision, with a 2% relative standard deviation at 0.5 ng ml^–1 and a detection limit (2σ) of 0.043 ng ml^–1. The accuracy and precision were assessed by performing replicate analyses on a number of coals, including NBS SRM 1632a bituminous coal, for which a mean value of 134 ng g^–1 and a standard deviation of 3.1 ng g^–1 were obtained. The excellent sensitivity, precision and extended linear working range of the method (5 ng g^–1 to 25 µg g^–1) are noted.