Determination of the Recovery of Dimethylmercury and Diphenylmercury Extracted From Organic Solvents and a Liquid Condensate With Bromine Water Using Cold Vapour Atomic Absorption Spectrometry

Abstract

Cold vapour atomic absorption spectrometry was used to determine if bromine water extracts organic bound mercury quantitatively from liquid hydrocarbons. The method described is used for mercury determination by the oil industry but has not been previously published. It presents an extension to the existing standard ISO 6978: 1992 which deals with the determination of mercury in natural gases. The bromine oxidises the mercury to mercury(II)-ions. Then excess bromine is reduced by hydroxylammonium chloride to bromide. Finally the mercury(II)-ions are reduced by tin(II)-chloride to elemental mercury. The absorbance at 253.7 nm is measured spectrometrically and depends linearly on the mercury concentration. Quantitative tests of this method have been carried out previously on organic mercury compounds dissolved in water and living tissues. Test results on the validity of this method for organic mercury compounds dissolved in crude oils or condensates are presented in this communication. The recoveries of dimethylmercury and diphenylmercury dissolved in an organic solvent and in a liquid condensate–solvent mixture have been determined. For dimethylmercury it was found to be 98 ± 5% in heptane and 98 ± 6% in a condensate–heptane mixture. For diphenylmercury the recovery was found to be 93 ± 5% in a heptane–toluene mixture and 95 ± 5% in a heptane–toluene–condensate mixture.