Determination of phosphorous and sulfur in environmental samples by electrothermal vaporization inductively coupled...

From the viewpoint of selective introduction of the analyte from its solvent and matrices, electrothermal vaporization (ETV) is useful for the sample introduction into the inductively coupled plasma (ICP). By using a tungsten boat furnace (TBF) vaporizer system, the loss of analyte phosphorus, which normally occurs during the drying and ashing stages, is suppressed. The phosphate ion is reacted with the tungsten supplied from the surface of the TBF to form stable tungsten phosphate species. Regarding the determination of sulfur, additional chemical modifiers such as copper(II), lead(II), etc., are necessary to retain the analyte on the TBF. The furnace-fusion (FF) method or wet-digestion technique on the TBF is applied to unify the chemical forms of the analytes. Various oxidative and reductive inorganic compounds as well as organic compounds of phosphorus and sulfur show the same sensitivities after the FF digestion with hydrogen peroxide. The detection limits are 1.5 ng and 0.12 ng for phosphorous and sulfur, respectively. The repeatabilities in terms of the relative standard deviations of 10 replicate measurements of phosphorus and sulfur are 4.2% and 2.0%, respectively. Finally, the established method is applied to the determination of several environmental waters.