Determination of dissolved mercury(II) in rainwater by heat-vaporization atomic absorption spectrometry after sorption with zinc(II) sulfide

A simple preconcentration method based on the sorption on zinc(II) sulfide has been developed for the determination of dissolved mercury(II) in rainwater. Commercially available zinc(II) sulfide (100 mg) was layered on a membrane filter (47 mm of diameter, 0.2 μm of pore size) after grinding in a mortar for approximately 2 min. When up to 500 mL of sample solutions passed through the zinc(II) sulfide-layered filter at a flow rate of 10 mL min^-1 or less, ng levels of mercury(II) in the solutions could be quantitatively collected on the filter. By heating the layered zinc(II) sulfide on a ceramic boat together with the filter, the collected mercury(II) could be vaporized as mercury(0) vapor and determined by atomic absorption spectrometry. The detection limit was 0.9 ng L^-1 (3σ, n = 6) when 500 mL of the sample solution was used. The proposed preconcentration method was applicable to the determination of dissolved mercury(II) in rainwater.