INSITU CONCENTRATION OF MERCURY-VAPOR IN A PALLADIUM-COATED GRAPHITE TUBE - DETERMINATION OF MERCURY BY ATOMIC-ABSORPTION SPECTROMETRY

A method was developed for the determination of mercury by cold vapour generation electrothermal atomic absorption spectrometry with in situ concentration in a palladium-coated graphite tube. The mercury vapour generated by using NaBH4 is rapidly trapped in the graphite tube, coated with PdCl2, at 250-degrees-C and atomized at 2200-degrees-C. The experimental results show that the trapping efficiency for mercury by PdCl2 is better than that by reduced palladium. Reduction of PdCl2 to palladium metal gives less favourable mercury trapping. Calibration is achieved with simple aqueous solutions. An absolute detection limit (3sigma) of 31.4 pg, corresponding to a concentration detection limit of 628 pg l-1 for 50-ml samples, is obtained. The characteristic mass is 114 pg. The precision for ten replicate determinations is 2.0% (relative standard deviation) at the 1-ng level and 1.8% at the 5-ng level. The method was successfully applied to the determination of mercury in certified water samples, sea water and waste water. The most favourable aspects of the method are its simplicity, high-speed and good reproducibility.