EFFECTS OF SAMPLE GEOMETRY ON INTERELEMENT QUANTITATION IN LASER MICROPROBE MASS-SPECTROMETRY

The effects of sample geometry on elemental quantification by laser microprobe mass spectrometry using the relative sensitivity factor (RSF) approach are addressed. Experiments are described that were conducted to optimize the laser and spectrometer conditions to achieve the best ion intensity characteristics for quantitative analysis. Data were collected under identical laser and spectrometer conditions from three sample geometries (thin film, spheres, and shards) bearing the same nominal elemental glass composition. The absolute elemental signal intensities and calculated RSFs are compared. The best precision for all elements, 16-29%, is achieved for the thin film sample for RSFs referenced to barium. For particles, the precision is, at best, 20-40%, with an accuracy of a factor of two, for elements with low ionization potentials referenced to other elements with low ionization potentials. The non-planar particle geometries result in variations in laser focus, power density and analytical volume which hinder quantification.