Some studies of the analytical utility of hollow cathode lamp-excited atomic fluorescence in an inductively-coupled plasma

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Description: A commercially available Inductively Coupled Plasma - Atomic Fluorescence Spectrometer (Baird Corporation, MA, Model Plasma/AFS - 2000) has been used in order to study the analytical utility of atomic fluorescence in an argon ICP. In some studies, the argon was doped with propane or oxygen. Multi-element determinations over wide concentration ranges in aqueous media have been studied. Optimum operational conditions, matrix interferences, and acid effects for single- and multi-element determinations have been investigated. Experimental results have shown that the atomic fluorescence technique provides excellent detection limits and accuracy for both trace and major element determinations. Linearity of calibration curves are also studied and method of enlarging linearity of calibration curves provided. Studies have also been done on the introduction of various organic solvents into an ICP. Important ICP parameters, such as incident power, nebulizer gas flow rate, sample uptake rate, and aerosol desolvation have been studied on with respect to their effects on relative intensities of atomic fluorescence in organic solvents in multi-element mode. Solvents studied include dimethylformamide (DMF), dimethylsulfoxide (DMSO), ethanol, kerosene, methanol, and xylenes. Signal background ratios have been also studied. It was found that the introduction of propane or oxygen to the argon ICP can in some cases increase the signal-to-background ratios for most elements studied and improve detection limits. The effects of doping gas flow rates and solvent properties on signal intensities, signal-to-background ratios, detection limits, plasma appearance, and atomic fluorescence spectra were also investigated. It has been found that the plasma appearance is dependent on the properties of solvents, the flow rates of doping gases, and the plasma operational conditions. Surfactant effects have also been investigated in order to understand the general function of surfactants in atomic spectrometry. Studies have been done on the effects of surfactants dodecylpolyxyethylene(23) alcohol (Brij-35), p-t-octylarypolyether alcohol (Triton X-100), sodium dodecyl sulfate (SDS), and tetradecyltrimethyl ammonium bromide (TDAB) on the relative intensities of atomic fluorescence signals of various elements. A model of surfactant function in atomic spectrometry in term of signal enhancements has been proposed. By using this model, successful explanation of some surfactant effects has been achieved. Scattered light and possible spectral interferences have been studied. Methods of correction have been established and acceptable results are obtained. The determinations of minor and major elements in food and agricultural samples have also been done using the ICP-AFS technique. Acceptable accuracy and precision are shown by the agreement of the ICP-AFS results with the certified results of NBS (newly named as the National Institute of Standards and Technology (NIST)) standard reference materials.
Language: English
Format: Degree Work