Download or read book Fundamental Studies and Applications in Microwave-induced Plasma Optical Emission Spectrometry written by Charles Bryson Williams (III) and published by . This book was released on 2019 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microwave-induced plasma optical emission spectrometry (MIP OES) is a technique within Atomic Spectrometry which is rapidly growing, following the relatively recent introduction of a complete commercial instrument based on the Hammer-cavity MIP. It offers advantages of low cost and simple operation, as well as the ability to run on air, enabling it to be used in remote areas or places with underdeveloped infrastructure. Due to the relative novelty of the technique, intensive method development for specific sample types is necessary to expand the utility of the technique and compensate for some of its limitations, such as its relatively low robustness and sequential detection. In addition, developments in plasma diagnostics and novel calibration strategies are also important to help increase the prominence and utility of the technique. The present research covers several such applications and efforts to improve instrumentation performance, as well as more fundamental studies of the properties of the plasma. In the first project, a method was developed to determine concentrations of Ca, K, and Na in various soft drinks. Addition and recovery experiments were used to evaluate the accuracy of the method. This study shows the ability of the technique to withstand relatively complex matrices, with no sample preparation other than simple dilution, and produce accurate results with traditional calibration methods. The second project involved development of a rapid dry-ashing technique to prepare samples for analysis using MIP. Calcium, Fe, K, Mg, Na and Zn were determined in complex-matrix samples such as tomato leaves, cheese, butter, peanut butter, infant formula and biodiesel samples. General agreement was also found between MIP OES results from samples decomposed either by the dry-ashing method or by a conventional microwave-assisted digestion procedure, and accurate results were found when applying the new, simpler method in certified reference material analyses. In the third project, several molecular species, naturally occurring in the plasma, were evaluated for their use as a plasma diagnostic tool. The N2+ / OH emission intensity ratio was evaluated for identifying the best instrumental operating conditions in MIP OES. Aluminum, Ba, Mn, Sr and Zn (analytes), and high concentrations of C, Na, Ca, HNO3 and HCl (sample matrices) were used as models to investigate the effects of complex matrices on analyte recoveries. The N2+ / OH signal ratio was more sensitive to changes in plasma conditions than the traditionally-used Mg II / Mg I ratio. Some other advantages include real-time monitoring capabilities, and the possibility of independently tracking variations in both plasma and sample introduction. Significant improvements in accuracy were achieved by employing the analyte-to-molecular species signal ratio, or their product, for calibration. In the final project, a novel calibration method, multi-flow calibration (MFC), was proposed. This strategy involves the use of multiple nebulization gas flow rates in the analysis to mitigate error caused by employing suboptimal sample introduction conditions, and to eliminate the need for optimization of conditions. The new calibration method was applied to the determination of Cr, Cu, Fe, and Mn in water and food samples. Addition recovery experiments and certified reference materials were used to validate the method. Multi-flow calibration presents comparable or superior accuracy to the traditional external standard calibration (EC), and offers simpler sample preparation than EC, requiring only a single standard and no modification of the sample introduction equipment.