Comparison of laser microprobe mass spectrometry (LMMS) and micro particle induced X-ray emission (micro-PIXE) for the analysis of senile plaques in Alzheimer's disease: A preliminary study

Results of micro-PIXE analysis of senile plaques (SP) in Alzheimer's disease (AD) brain have been utilized to independently confirm levels of iron (Fe) as measured by LMMS in adjacent brain sections. LMMS concentrations were calculated based on the preparation and analysis of an iron calibration curve prepared in our laboratory. The LMMS standards consist of iron cis-dicyclohexano-18-crown-6 ether coordination complexes dissolved in Spurr's low viscosity embedding medium. To our knowledge, this is the first report of the use of micro-PIXE, with its spatial resolution and detection limits comparable to that of LMMS, in the validation of LMMS results. The agreement observed between results obtained for Fe by micro-PIXE and LMMS indicates that the use of our LMMS standards, at least in the case of Fe, yields accurate results.