Research

SPECIATION ANALYSIS OF MERCURY

The use of chemical generation of alkyl-substituted Hg species by NaBH₄ reduction for speciation analysis of mercury was explored [1]. Two reaction media, HCl and TRIS buffer were investigated to determine analytically important Hg species such as Hg²⁺; MeHg⁺; EtHg⁺ and PhHg⁺. Severe changes in speciation information during HG were identified regardless of the reaction medium employed. Cryogenic trap (CT) coupled to ICP-MS detector was used for identification of the species and quantification of the degree of their decomposition. The degree of de-alkylation/de-arylation was 45%, 71% and 94% for methyl-, ethyl- and phenylmercury in HCl medium. Slightly better results were achieved for VSG from TRIS buffer medium in which the degree of de-alkylation/de-arylation reached 6%, 28% and 99% for methyl-, ethyl- and phenylmercury. As a consequence, attention should be paid to these conclusions by analytical community and perhaps some standard operation procedures for Hg speciation analysis by VSG-CT/GC should be revised.

Two simple approaches to speciation analysis of mercury in flue gases have been developed distinguishing between two most abundant Hg species, elemental mercury (Hg⁰) and oxidized form of mercury (often HgCl₂) either in off-line, or on-line measurement arrangements [2]. The off-line approach combines a pair of sorbents from which the first one traps oxidized form of mercury (HgCl₂) selectively on a raw alumina sorbent while the second one retains Hg0 quantitatively on a gold-coated alumina filling. The sorbents are commercially available and can be used repeatedly. The capacity of both sorbents was found satisfactory even for applications dealing with gases heavily polluted by mercury. The on-line approach to speciation analysis makes use of the fact elemental mercury can be detected by AAS at ambient atomizer temperature while sublimate as a molecular structure must be atomized at 900 °C prior to AAS detection. The temperature of the atomizer or even more advantageously the temperature of the gas line upstream the atomizer can thus be used to control the seciation analysis process. Both approaches are showing great potential to industrial/environmental applications owing to their simplicity, operator friendliness and low costs. Accuracy and precision reached is comparable or even better than that reached by current methods employed in industrial applications and environmental monitoring