New Approaches For Simultaneous Speciation Of Lead And Mercury Using GC-ICPMS

Pb and Hg are very toxic elements,which both come mainly from anthropogenic activities but follow different pathways of species transformation in the environment. Their toxicity and/or bioavailability,in addition to their mobility and their impact on the environment/organism,depend not only on their total concentration but also significantly on their chemical forms.In general,the monopositive cations behave as maximal toxic species that are derived by loss of one organic group from the neutral fully saturated organometal,e.g.(C₂H₅)₃Pb⁺,and CH₃Hg⁺.Interest in the environmental/biological pathways of organolead and organomercury compounds has been growing in order to elucidate and understand the biogeochemical cycles and the toxicity and/or bioavailability of Pb and Hg for decades.To this end,novel and sophisticated analytical methods have played a crucial role,and it is now recognized worldwide that one has to rely on a combination of chromatographic separation techniques with structure-selective and/or element-specific detectors in most cases of real-life analytical speciation.The main contributions of this thesis are that 1) designing and constructing a novel thermo-diffusion interface(TDI) in order to couple capillary gas chromatography(cGC) and inductively coupled plasma mass spectrometry(ICPMS) for simultaneous speciation of inorganic and organic Pb and Hg species;2) synthesizing tri-n-propyl-lead chloride(Pr₃PbCl),which was used as a new internal standard(IS) for simultaneous speciation of Pb and Hg;3) applying cGC-TDI-ICPMS and using Pr₃PbCl as an IS to determination and speciation of Pb and Hg as well as other heavy metals and metalloids in time-resolved peat bog and tree bark pocket samples for evaluating the historical trend and degree of environmental pollution. This thesis consists of 5 chapters as below:In Chapter One,the abundance and existing species of Pb and Hg in the environment as well as their toxicities were briefly introduced;the current strategies of Pb and Hg determination and speciation have been reviewed briefly including the sample pretreatment and separation and detection techniques as well.Research proposal was thus made for this thesis,aiming to develop novel interface for coupling cGC and ICPMS,and synthesize new IS for simultaneous speciation of Pb and Hg in environmental and biological samples.In Chapter Two,a novel thermo-diffusion interface was designed and constructed for the effective coupling of cGC and ICPMS.After optimization of sample preparation and derivatization of target Pb and Hg species as well as the instrumental conditions have been performed,in which butyl magnesium bromide(BuMgBr) was used as a derivatization reagent to distinguish different Pb/Hg species the sample,the speciation of common inorganic and organic Pb and Hg species could be achieved within 7 min.The method detection limits for Pb²⁺,Me₃Pb⁺,Me₄Pb,Et₃Pb⁺,Et₄Pb and Hg²⁺,MeHg⁺,EtHg⁺ are 7.0 pg g^-1,0.04 pg g^-1,0.07 pg g^-1,0.06 pg g^-1,0.06 pg g^-1, 0.2 pg g^-1,0.09 pg g^-1,0.1 pg g^-1,respectively;the recoveries of lead and mercury species are between 92.2-110%.In Chapter Three,tir-n-propyl-lead chloride was synthesized and used as a new IS for simultaneous speciation of Pb and Hg by cGC-TDI-ICPMS using BuMgBr as a derivatization reagent.The accuracy of the developed method has been validated by analyzing the certified reference materials including CRM 580(estuary sediment), CRM 463(tuna tissue) and NIST 1946(lake superior fish tissue).This method was finally applied to the speciation of Pb and Hg in the seafood and sediment samples collected around and/or on Xiamen Island.In Chapter Four,the method established was further applied to determination and speciation of Pb and Hg as well as other heavy metals and metalloids in the time-resolved samples peatbog and tree bark pocket.Historical pollution trends of these pollutants have been revealed using the information obtained using cGC-TDI-ICPMS together with Pb isotope analysis,which was recorded in peatbog and/or tree bark pocket samples.In Chapter Five,a summary and prospective of this thesis.