AN IMPROVED SPECIATION METHOD FOR MERCURY BY GC CVAFS AFTER AQUEOUS-PHASE ETHYLATION AND ROOM-TEMPERATURE PRECOLLECTION

An improvement has been made in previous mercury speciation methods, which omits the use of liquid nitrogen by modifying the GC conditions. In addition, the sometimes observed thermal decomposition of ethylation derivatives in the process of desorbing the compounds to the GC column has been investigated and overcome. The resulting improvements have allowed simultaneous determination of methylmercury (MMHg) and inorganic mercury (Hg(II)). They have also increased the precision of the ethylation reaction and refined the MMHg determination. Optimal conditions for MMHg were confirmed and supplemented, while the parameters for dimethyl mercury (DMHg) and Hg(II) were thoroughly investigated for the first time. The absolute detection limits (DL) for 2sigma of the reagent blanks as Hg and about 0.6, 0.6 and 1.3 pg for DMHg, MMHg and Hg(II), respectively. The improved method is five-fold faster than the original method, allowing up to 80 samples to be analyzed within 8 hr.