Refinement of major- and minor-element PIXE analysis of rocks and minerals

• Precision calibration of PIXE system for quantifying major element constituents in silicates.
• Use of new mass attenuation coefficient database in GUPIX fundamental parameters analysis.
• Identification of and correction for an energy calibration non-linearity found in SDD spectra.
• PIXE quantification of major and minor constituents to within single percent accuracy.
• Results validated by previous electron microprobe and chemical analyses.

An attempt has been made to assess the accuracy of the particle-induced X-ray emission (PIXE) fundamental parameters with standards approach to quantifying major- and minor-element constituents of silicate glasses and minerals. A deviation from linearity at low energies in the channel-energy calibration relationship was identified as a source of undesired residues in GUPIX-fitting. A correction for this effect was developed using a general-purpose spectrum fitting program and was incorporated in GUPIX. The PIXE spectra of sixteen well-characterized electron microprobe standards were then processed. Complementary electron probe micro-analysis (EPMA) measurements were used to support the comparison of the PIXE results with previous characterizations. Major element concentrations were found to differ on average from literature values as follows: SiO2 (−0.28 ± 0.12%), Al2O3 (0.72 ± 0.74%), MgO (0.11 ± 0.63%), Na2O (−2.6 ± 1.2%), K2O (1.1 ± 0.7%), CaO (−0.35 ± 0.37%), TiO2 (2.5 ± 1.9%), MnO (0.8 ± 4.7%), FeO (0.98 ± 0.93%). These results indicate that major and minor elemental analysis can be achieved with high accuracy using the present Guelph micro-PIXE setup.