UBC Theses and Dissertations
Development of a laser ablation quadrupole ion trap mass spectrometer for direct spectrometry of solid samples Gill, Christopher George
Elemental analysis of solid samples often involves a dissolution step prior to analysis, which can introduce contamination and result in further dilution of trace analytes. Methods of direct solid analysis obviate this step, and can provide compositional information for solid materials. To achieve very low detection limits for analytes in solid samples requires special methodology. One way to achieve lower limits of detection is to increase the observation time for an analyte. Quadrupole ion traps have demonstrated single ion detection using laser based ion detection methods, making the combination of laser ablation for direct solid sampling and quadrupole ion trap mass spectrometry a logical choice for ultra-trace (sub-femtogram) analysis. This thesis examines the use of laser ablation coupled with quadrupole ion trap mass spectrometry as a potential analytical method for ultra-trace direct solid multielemental mass spectrometry. This thesis develops an analytical method for direct solid mass spectrometry, called Laser Ablation Ion Trap Mass Spectrometry (LAITMS). Through a series of investigations, a hybrid mass spectrometer has evolved which embodies many characteristics that are desirable for LAITMS analysis. The function of this new spectrometer was subsequently investigated by a series of parametric studies to determine optimum conditions for it’s operation as a simple mass spectrometer, capable of direct solid analysis. Parameters considered included laser irradiance & wavelength, ion storage field characteristics and sample surface quality. The use of modified hyperbolic electrodes as well as cylindrical electrode configurations has been examined. Selective ionization schemes for analytes in solid samples has been investigated by a two-color LAITMS experiment. The effect of synchronizing laser ablation with the phase of the ion storage field has also been examined. The present LAITMS spectrometer has demonstrated picogram detection limits for analytes present in samples of stainless steel. Future laser induced fluorescence ion detection schemes should realize much lower detection limits.
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