Atomic Absorption Determination of Ultratrace Elements in Geological Materials by Vapor. Hydride-Forming Techniques. I. Mercury

A method is described for the determination of mercury at nanogram levels in geological materials by flameless atomic absorption spectroscopy after metal vapor generation. Mercury is converted to a soluble form by H₂SO₄-HNO₃ attack in a teflon bomb at 180°C for 90 minutes. Metal Hg vapor is obtained by reaction with combined NaBH₄-NaOH using the Perkin-Elmer MHS - 10 hydride system and determined at room temperature. Mercury can be easily determined in most silicate materials. The sensitivity of the method depends essentially on the purity of the reagents and contaminations during handling rather than on instrumental capabilities. A detection limit of about 10 ng/g Hg for 0.5 g samples has been achieved with the use of normal "suprapure" reagents. Mercury contents on some USGS, CRPG and ANRT reference samples are reported.