Determination of mercury in pharmaceutical products by atomic-absorption spectrophotometry using a carbon rod atomiser

Abstract

An electrothermal atomisation procedure using a carbon rod atomiser is described for the determination of mercury after its extraction with dithizone (diphenylthiocarbazone) into chloroform. The increased stability of mercury after extraction allows drying and ashing to be carried out adequately without loss prior to atomisation. The sensitivity to mercury in the carbon rod atomiser is 1.1 × 10^–10 g to give 1% absorption at 253.7 nm. Calibration graphs are linear over the range 0.2–2.0 µg ml^–1 of mercury. The method can be applied directly, without a preliminary digestion procedure, to solutions containing organic mercurial preservatives or bactericides [phenylmercury(II) acetate or nitrate or thiomersal (sodium ethylmercurithiosalicylate)], and to trace determination in basic and some neutral and acidic compounds, soluble in water or in dilute acids. A standard additions procedure is recommended to overcome possible matrix effects, and to allow the detection of contamination errors. The results compare favourably with those obtained by the conventional cold vapour technique.