Determination Of Mercurial Species By The Coupling Of High Performance Liquid Chromatographv And Inductively Coupled Plasma Mass Spectrometry With Online Solid Phase Extraction Preconcentration

Mercury is one of the most poisonous and hazardous heavy metals on humans and higher animals in environment. The toxicity of mercury is highly dependent on its chemical form. So it is necessary to develop accurate and sensitive analytical methods to determine the chemical form of mercury. However, the concentrations of mercury species in unpolluted environmental samples are normally at trace and even ultra-trace levels. Hence, it is an arduous task to determine mercury species in these samples directly by most instrumemts. In these cases, offline and/or online preconcentration of analytes is desirable.Microfluidic chip analysis has attracted the interest of many researchers as it can decrease sample consumption to a range of several nanoliters to sub-microliters. When coupled with inductively coupled plasma mass spectrometry, scarce amount of sample can be analyzed.Firstly, the necessity of mercury enrichment, research progress of mercury enrichment, detection method and microfluidic chips were explained in detail.In the second chapter, a hyphenated method for mercury speciation analysis by the coupling of high performance liquid chromatography and inductively coupled plasma mass spectrometry with the online strong anion exchange column (SAX) preconcentration was developed. Hg analytes (Hg+, MeHg, EtHg and Hg2+) were absorbed on the SAX column preconditioned with sodium3-mercapto-l-propanesulfonate, and then rapidly eluted and separated by using different concentrations of2-mercaptoethanol solution as eluant and mobile phase within5min on a50-mm C18column. Under the optimized conditions, the enrichment factors of Hg+, MeHg, EtHg and Hg2+up to1025,1084,1108and1046-fold, respectively, and the detection limits were0.015,0.010,0.009and0.016ng L-1, respectively.In the third chapter, based on high affinities of thiol group to mercurial compounds, thiol-functionalized silica microspheres (SH-SiO2) were prepared from aminosilica by usage of3-mercaptopropionic acid for online mercury SPE preconcentration. A hyphenated method for mercury speciation analysis by the coupling of high performance liquid chromatography and inductively coupled plasma mass spectrometry with the online SH-SiO2packed SPE column preconcentration was developed. It was demonstrated to be an efficient adsorbent for the adsorption of mercury species with adsorption capacities of27.4mg g-1for Hg2+,62.1mg g-1for MeHg and59.6mg g-1for EtHg. Furthermore, the enrichment could be directly performed without any column preconditioning and thus greatly shortened the analysis time. With different concentrations of L-cysteine as eluent and mobile phase, rapid separation was achieved within8min on a150-mm C18column. Under the optimized conditions, each enrichment factor of Hg2+, MeHg and EtHg was830,916and883-fold and detection limits were0.019,0.013and0.014ng L-1respectively.In the forth chapter, a microfluidic chip-based nanoflow injection system was set up for inductively coupled plasma mass spectrometry. We succeeded in determining the trace platinum in human plasma samples by ICP-MS via a microfluidic chip with eight sampling channels for introducing sample at the nanoliter level. Under the optimized conditions,200nL sample was consumed and the absolute detection limit of this system for195Pt was2.54fg, which was improved by a factor of3200in comparison with the conventional sampling system. Furthermore, the present method had higher accuracy and precision.A conclusion was made on the basis of the above work in the final chapter followed by the plan for the next research direction.