A Combustion-Trapping Pretreatment Technique for Environmental Samples and Its Application in Mercury Isotopic Analysis

KeyWord:combustion-trapping  environmental samples  mercury isotope  pretreatment

Abstract:

      High-precision determination of mercury isotope ratios using multi-collector inductively coupled plasma mass spectrometry(MC-ICP-MS) requires high quality of sample pretreatment.Different kinds of pretreatment methods developed for liquid,solid and gaseous samples may result in certain systematic errors.This study aimed at unifying the pretreatment techniques of different kinds of environmental samples.Mercury in samples was enriched and transformed into absorbable solid state and then adsorbed onto a solid carrier,including gaseous elemental mercury in gaseous samples enriched with gold column,dissolved gaseous mercury and total mercury in liquid samples enriched with purge and trap method and particulate mercury in the atmosphere collected with membrane filter method.Solid sample was combusted in a tube furnace.An acidic absorbing solution with potassium permanganate was adopted to absorb Hg2+that was oxidized from Hg0 produced in the combustion.Finally,the absorbing solution was analyzed by MC-ICP-MS.The parameters,including oxygen gas flow rate,volume of absorbing solution and concentration of potassium permanganate,were optimized.Method blank,recovery and precision of the method were investigated.The established method was applied in the sample pretreatments of gaseous elemental mercury and particulate mercury in the atmosphere,dissolved gaseous mercury in seawater,total mercury in rain and soil.The isotopic compositions of mercury in the samples were analyzed and discussed.