Determination of Mercury in Small Quantities in Biologic Material by a Modified Photometric-Mercury Vapor Procedure.

Abstract

A modification of the Jacobs-Yamaguchi method of determining Hg is presented. In the original meth-od Hg is extracted with dithizone in chloroform from incompletely di-gested samples. The dithizone-Hg complex is subjected to heat de-struction and the resulting Hg vapor is determined photometrically. This method suffers from some disadvantages among which is a low and uncertain maximum deflection because of a lengthy evaporation period for the Hg vapor during the heat destruction of the dithizone-Hg complex, and in some cases background readings from interfering substances. In the presented modification the Hg vapor is absorbed on Au and then released again rapidly by mild heating of the Au filter. The method results in comparatively high reading even with amounts of Hg as low as 5 ng [nanograms]. The coefficient of variation of determinations of Hg in a standard solution has been found to be about 30%, when amounts of Hg varying from 5 to 100 ng were determined. The method has been controlled by comparison with neutron activation analyses and scintil-lation analyses of radioactive Hg. These comparisons show that analysis of samples containing more than 10 ng of Hg per g can be made with the photometric method to give results of the correct order of magnitude. Silver or Cu will not influence the determinations. Iodide, however, will inhibit the extraction of Hg from the digest solution when present in amounts of the same order of magnitude as the Hg itself.