SENSITIVITY IMPROVEMENTS IN THE DETERMINATION OF MERCURY IN BIOLOGICAL TISSUES BY NEUTRON-ACTIVATION ANALYSIS

The possible association of dental amalgam surface exposure, brain mer cury (Hg) levels, and pathological markers of Alzheimer's disease (AD) in the brain is the subject of an on-going study in our laboratory. T wo radiochemical neutron activation analysis methods and the use of in strumental neutron activation analysis (INAA) with Compton suppression spectrometry have been evaluated for improving our INAA Hg detection limit (2.8 +/- 0.6 ng/g, wet-weight basis) in human tissue. Large numb ers of samples dictated the use of a purely instrumental method or rap id simple radiochemical separations. Human brain tissues and NIST biol ogical standards were analyzed using a precipitation of (HgCl2)-Cl-2, a solvent extraction utilizing sodium diethyldithiocarbornate, convent ional INAA, and INAA with Compton suppression. The radiochemical preci pitation of Hg2Cl2 proved to be the most useful method for use in our study because it provided a simultaneous, quantitative determination o f silver (Ag) and a Hg detection limit in brain tissue of 1.6 +/- 0.1 ng/g (wet-weight basis).