Method and instrumental development for ultra-trace elemental and speciation analysis

Ultra-trace elemental and speciation analyses, along with the relevant instrumentation and methodology, are important aspects on which modern analytical chemistry is focusing intensively. Therefore, this dissertation endeavors to address some challenges posed in this field.; First, method and instrument development for ultra-trace elemental analysis using microwave-enhanced clean chemistry is investigated. A novel dual-vessel design has been developed and has demonstrated an effective use of an efficient, controllable, and cost-effective sample preparation technique for the determination of ultra-trace impurities in silicon material. The technique further demonstrates the capability of the total retention of many traditionally volatile species at ultra-trace level by applying unique microwave heating and cooling mechanism.; Second, new concepts of isotope dilution method are investigated to improve long-term stability and to enhance threshold of the ultra-trace element at instrumental detection limit. These new concepts have been demonstrated using the instruments of Inductively Coupled Plasma Mass Spectrometry and Electro Spray Mass Spectrometry to determine ultra-trace elements over an extended period of time. Consistent improvement in both precision and accuracy demonstrate the general applicability of new concepts to enable the mass spectrometer system to function for an extended period of time and to reduce the error caused by instrument drifts and conventional calibrations. A new threshold method using IDMS to enhance the quantitative capability of the MS instrument is also evaluated and established. The enhancements both near and at instrument detection limit are evidenced using Monte Carlo simulation. Portions of this study are patent pending.; Third, a sequential extraction method for mercury speciation in a soil matrix is established based on the mobility and toxicity of different mercury species. The most mobile and toxic mercury species, including alkyl mercury and soluble inorganic mercury species, are extracted using an acidic ethanol solution. The extracts can be further separated by the SCF-SPE-DMA-80 or by the HPLC-ICP-MS. The inorganic mercury remaining after the ethanol extraction can be further speciated by sequential acid extraction. The method is a promising candidate for on-site screening for mercury speciation and laboratory quantitation for mercury speciation, especially for ultra-trace alkyl mercury species.