Reduction of organic mercury in water, urine, and blood by sodium borohydride for direct determination of total mercury content.

We have established the optimal conditions for use of sodium borohydride as the reducing agent before the direct determination of mercury in water, urine, and blood by atomic absorption spectroscopy. We evaluated the effects of pH, temperature, and cupric sulfate concentration on the direct determination of both organic and inorganic compounds of mercury. Accurate and precise quantification of mercury requires that the pH be between 9.3 and 9.5, the reaction temperature above 25 degrees C, the reaction time longer than 1 min, and, for urine samples only, the cupric sulfate concentration 10 mumol/L. The detection limit of the method is 1 to 2 ng and the precision (CV) is 3.8% for blood and 4.0% for urine.