DETERMINATION OF MERCURY SPECIES IN GAS-CONDENSATES BY ONLINE COUPLED HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND COLD-VAPOR ATOMIC-ABSORPTION SPECTROMETRY

A method for the speciation of mercury in gas condensates is reported, Mercury(II) chloride (HgCl2), methylmercury chloride (MeHgCl), phenylmercury acetate (PhHgAc) and diphenylmercury (Ph(2)Hg) are separated by reversed-phase high-performance liquid chromatography (HPLC) using gradient elution, Prior to the determination, the organic ligands and the matrix were destroyed by oxidation with K2Cr2O7. Mercury is detected with cold-vapor atomic absorption spectrometry (CVAA), where the mercury compounds are reduced to metallic mercury by a treatment with NaBH4. In a continuous-flow system the concentrations of the reagents used are optimized using a modified simplex algorithm, Detection limits for mercury are at the 10 ng ml(-1) level, Analysis of multi-compound mixtures indicates that chemical reactions between HgCl2 and Ph(2)Hg and between MeHgCl acid Ph(2)Hg take place, The method developed was applied to the speciation of mercury in gas condensates and did not require use of any solvent extraction or chemical derivatization steps, In the gas condensates, mercury(lI) compounds were found to be present at the 100 ng ml(-1) level.