Stability and reactions of mercury species in organic solution†

Abstract

The stability over time of elemental mercury, methylmercury and inorganic mercury species was evaluated in heptane, toluene and mixed hydrocarbon solutions. Elemental mercury and inorganic mercury(ii) were determined using a specific extraction method followed by ICP-MS or CVAAS. Methylmercury and mercury(ii) were determined by GC-MIP-AES after derivatisation with Grignard reagent. The results show that significant losses of mercury species from solution can occur by two pathways: by adsorption on the container wall and by reactions forming mercury(i) compounds. For the latter pathway, rapid losses of dissolved elemental mercury and mercury(ii) chloride species occur when both are present in solution. For heptane solutions containing HgCl 2 , 80% of the HgCl 2 remains after 13 d in a pure standard compared with 11% in a standard containing Hg 0 . Mercury(i) compounds form a colloidal material, which is not soluble in these organic solvents at a detectable concentration. Mercury(i) compounds were butylated with Grignard reagent to form the organic mercury(i) compound (C 4 H 9 ) 2 Hg 2 that was measured specifically by GC-MIP-AES and GC-MS. This new compound was stable and appeared to precipitate from solution.

Analytical Methods for Speciation of Mercury in Gas Condensates: Critical Assessment and Recommendations

“…In this procedure total inorganic mercury (referred to as the sum of Hg 2+ and Hg°) was converted by Grignard reaction to Bu 2 Hg. Note that in another work (Snell et al, 1998) the same authors observed that Hg°did not react with the Grignard reagent and underwent butylation. Ionic Hg (Hg 2+ ) was extracted from gas condensates into an equal volume of water.…”

“…Another important reaction leading to analytical errors is the formation of Hg (I) compounds from the dissolved Hg°a nd HgCl 2 . Both Hg°and HgCl 2 , if present alone in standard solutions, are relatively stable, with half-lives of 10 d and few months, respectively (Snell et al, 1998). However, when both Hg°and HgCl 2 are present their concentration rapidly decreases with time as a result of the Hg 2 2+ precipitation.…”

Species specific isotope dilution calibration for determination of mercury species by gas chromatography coupled to inductively coupled plasma- or furnace atomisation plasma ionisation-mass spectrometry

“…Preliminary tests with natural mercury indicated that the reaction between the species may be concentration dependent as it occurred very slowly at concentrations of 10 mg l 21 (of each species) and has not been observed in solutions at trace (v1mgl 21 ) concentrations. 10 The atom fractions taken for isotope dilution calculations were those determined by ICP-MS analysis of the aqueous solution. The ICP-MS determined isotopic fractions were all within 0.3% of the values certi®ed for the enriched standard, as shown in Table 1, and the isotopic fractions of a natural mercury standard were within 0.3% of literature values.…”

“…In particular, variation in the conductivity of samples in organic solutions could lead to dif®culty in forming a stable electrospray, and the possibility of accurate quantitation would be further reduced by matrix effects and non-linearity of the analyte mass± detector response relationship. Positive identi®cation with the possibility of quanti®cation may be achieved with a reference technique such as gas chromatography (GC) coupled to electron impact mass spectrometry (EI-MS) 10 or glow discharge mass spectrometry (GD-MS). Ideally, a source that may be conveniently and rapidly switched between providing sensitive elemental detection and molecular information for identi®cation could be applied.…”

“…10 Consequently, methods were developed for the determination of a number of different organic mercury species in condensates. 17±21 To use isotope dilution calibration for mercury speciation methods for this matrix, it is therefore essential that a number of different mercury species are used.…”