An automatic microgravimetric screening system based on piezoelectric detection and the use of acidic stannous chloride as reductant was developed for the fast detection and determination of total mercury in water. Reduced mercury is detected as an amalgam by using a gold-coated piezoelectric crystal, the sensor subsequently being regenerated by passing it through a peroxydisulfate solution. The gold-coated piezoelectric crystal is a highly efficient retention unit for the main soluble mercury species (inorganic, complexed, and organometallic) previously reduced to elemental mercury and is free of interferences from other metal ions. This detector exhibits good sensitivity: it allows the determination of mercury at sub-parts-per-billion concentration levels (0.30-1.00 microg/L). The precision, expressed as relative standard deviation, was +/- 2.7% (n = 11; P = 0.05) at 0.5 microg/L total mercury. The proposed method was successfully used as a rapid screening method for mercury monitoring in natural waters.

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