A METHOD BASED ON ICP-MS FOR THE ANALYSIS OF ALZHEIMERS AMYLOID PLAQUES

Inductively coupled plasma mass spectrometry (ICP-RIS) was combined wi th now injection (FI) and a selective extraction procedure (which isol ates Alzheimer's amyloid plaques) for the multielemental analysis of p laque cores. FI-ICP-MS was also used to analyze the various reagents i nvolved in the sample preparation to determine whether they were the s ource of the various elements detected in the plaque samples, An exter nal calibration with matrix-matched standards (in terms of salt concen tration) was carried out in all cases, The concentrations of Cr, Mn, N i, Cu, and Pb were in the 0.2-0.8 mg L-1 range whereas that of Al, Fe, and Zn were 2-20 mg L-1 in the plaque sample, These values can be tra nslated into a microgram per gram level in the plaque core by multiply ing them by 29-500 (the exact factor depends on the weight of the plaq ues, which were not dried to prevent the loss of volatile elements), A lthough spectroscopic interferences arising from matrix elements of th e sample cannot be ruled out in the case of Al, Cr, Ni, Cu, and Fe, th e large levels detected (especially for Al and Fe), compared to the mu ch lower or undetectable levels in the various reagents, strongly sugg est the accumulation of these elements by the AD patient during life r ather than contamination during sample processing.