Microdetermination of mercury in biological samples. Part II. An apparatus for rapid automatic determination of mercury in digested samples

Abstract

Urine samples that have been cold-digested by potassium permanganate-sulphuric acid mixture overnight are analysed in apparatus consisting of an automatic sample changer, pumps for transferring the sample solution to a purgation tower and adding tin(II) chloride solution, which reduces mercury(II) to metallic mercury, and a spectrophotometer. The mercury vapour is liberated from the solution in the tower by a flow of nitrogen and then taken through the absorption cell in the spectrophotometer where the light absorption at a wavelength of 253·7 nm is continuously recorded. After completion of the purgation, the mercury-free solution is transported back to the original tube in the sample changer by reversing the pumps, and the next analysis is started. The mercury content in the sample is calculated from standard graphs drawn from results with known amounts of mercury. Sixty digested samples, each containing 1 ml of urine, are analysed in about 2 hours without any manual work or supervision. In each sample about 1 ng of mercury can be detected, but normally the working range for urine samples is 0 to 400 ng ml^–1 of mercury(II). The analysis can be applied to biological or any other samples that can be digested in a similar manner.