Pre-concentration technique for cold-vapour atomic-fluorescence determination of mercury in drinking waters

Abstract

Direct determination of mercury by cold-vapour atomic fluorescence is insufficiently sensitive to monitor nanogram per litre levels of mercury in raw and potable waters. A simple method of sample pre-concentration that utilises a permanganate solution trap is described. The pre-concentration step takes 5 min per test and requires only 250 ml of sample. The procedure has a limit of detection of 1.6 ng l^–1 with a total standard deviation of less than 2 ng l^–1 or 7% of the concentration. The method results in a bias of less than 3 ng l^–1 or 10% of the concentration for both inorganic and total mercury and has a linear range of 0–700 ng l^–1. Suitable procedures for digestion of organomercury complexes using potassium persulphate and for preservation of samples for periods of up to 1 week by addition of potassium dichromate and nitric acid are also described.