DETERMINATION OF TOTAL HG IN ENVIRONMENTAL-SAMPLES WITH ONLINE MICROWAVE DIGESTION COUPLED TO A FLOW-INJECTION MERCURY SYSTEM (FIMS)

A system is described that fully automates the digestion and determina tion of total mercury in environmental samples (drinking waters, waste waters, and sediments). Once appropriate digestion reagents are added to the sample, the entire system operation occurs in a standalone mann er. The time required for sample digestion has been reduced from betwe en a half hour and two hours to less than one minute, resulting in thr ee replicate determinations of a single sample being performed in five minutes. The system demonstrates exceptional accuracy for drinking wa ter and wastewater samples spiked with inorganic mercury and methyl-me rcury chloride, wastewater samples digested off-line and analyzed with conventional flow injection-mercury cold vapor AAS, and spiked and un spiked certified sediment samples. The precision for a 10-ng/mL Hg sta ndard is comparable to that obtained without on-line microwave digesti on (1.1% RSD, n = 3). The detection limits for the on-line microwave d igestion-FIMS combination are also quite low due to the exceptional st ability of the FIMS, with an instrument detection limit (IDL) of 0.014 ng/mL Hg and a method detection limit (MDL) of 0.035 ng/L Hg for a 50 0-mu L sample volume. Since the entire analytical process occurs in a closed system, opportunities for contamination are greatly reduced, le ading to greater analytical quality and enhanced laboratory productivi ty.