Problems Encountered During the Development of a Method for the Speciation of Mercury and Methylmercury by High-performance Liquid Chromatography Coupled to Inductively Coupled Plasma Mass Spectrometry

Abstract

A study was carried out to develop a method for the determination of methylmercury and inorganic mercury by coupling HPLC to ICP-MS. During the course of this work it was noted that the use of stainless-steel components in the HPLC system led to adsorption of the mercury compounds, which was more pronounced with mercury(II) chloride than methylmercury. In particular, the use of a stainless steel sample loop led to larger peaks for both compounds, but particularly inorganic mercury, compared with a PEEK loop. The type of loop used had no effect on the separation of these compounds on an ODS column using a mobile phase composed of 10 mM tetrabutylammonium bromide and 60% methanol. However, both of the two ODS stainless-steel columns tested adsorbed the compounds to some degree, leading to a slow bleed of mercury. The use of components made with materials other than stainless steel, e.g. , PEEK sample loops and glass-lined columns, and inclusion of a sulfur ligand in the eluent (2-mercaptoethanol) reduced these problems significantly.