A CONTINUOUS MONITORING-SYSTEM FOR TOTAL MERCURY IN WASTE-WATER BY COLD VAPOR ATOMIC-ABSORPTION SPECTROMETRY AND CONTINUOUS MICROFLOW ANALYSIS

An automated system based on "continuous microflow analysis" and cold vapor atomic absorption spectrometry has been developed for monitoring the concentration of total mercury at sub-mu-g/l levels. The method involves a continuous microflow technique for sample digestion, reduction and extraction in small bore tubes (0.5 mm i.d.) at mu-l/min flow rates of reagents. Sodium tetrahydroborate in sodium hydroxide solution was used as the reducing reagent. In the case of discrete injection of sample (200-mu-l), analysis time for the determination of total mercury was about 3 min per sample. The detection limit of mercury(II) was 0.15-mu-g/l (S/N = 3) for a gas flow cell of 40 mm path length. The relative standard deviation was 0.99% at 4.0-mu-g Hg/l (n = 10). The calibration curve was linear up to 5.0-mu-g/l. Under the optimal conditions, the present method could be successfully applied to the continuous monitoring of total mercury in waste water.