COLD-VAPOR GENERATION FOR INDUCTIVELY-COUPLED ARGON PLASMA-ATOMIC EMISSION SPECTROMETRIC ANALYSIS .3. MERCURY

A method is presented for the determination of total mercury in enviro nmental samples by inductively coupled argon plasma/atomic emission sp ectroscopy (ICP/AES) using cold-vapor generation. A 1.0 g or 10 mt tes t portion is digested 6-12 h in a 16 x 150 mm, 10 mL volumetric test t ube at room temperature and is subsequently digested on a programmed h eating block at 95 degrees C with trace-metal grade nitric acid. The d igested samples are next treated with potassium permanganate and heate d between 70 and 95 degrees C; thereafter, oxalic acid is added to rea ch the final endpoint. The mercury(ll) is reduced by sodium borohydrid e in a simplified continuous manifold. A standard pneumatic nebulizer effects the gas-liquid separation of mercury. Mercury is quantitated b y ICP/AES at 194.232 nm. The instrument detection limit for the method is 0.2 mu g/L. Water samples are analyzed directly. The detection lim it is below the current National Primary Drinking Water Standard Maxim um Concentration Limit of 2 mu g/L for mercury. For a 10:I dilution of a nominal 1.0 g solid test portion, the detection limit is 2.0 mu g/L . This concentration is also less than the regulatory limit of 200 mu g/L for the U.S. Environmental Protection Agency's Toxicity Characteri stic Leaching Procedure. The quantitation is linear up to 300 mu g/kg. The method demonstrated statistical control for samples of biological and environmental interest.