Membrane solubilization with tetramethylammonium hydroxide for the preconcentration and electrothermal atomic absorption spectrometric determination of trace amounts of arsenic in water

Abstract

Solubilization of a mixed cellulose ester membrane filter (MF) with tetramethylammonium hydroxide (TMAH) is proposed for the preconcentration and electrothermal atomic absorption spectrometric (ETAAS) determination of trace amounts of arsenic in water. Arsenic at not more than 0.4 µg in 100 ml of sample solution was retained on the MF by filtration as an ion associate of arsenomolybdate and tetraphenylphosphonium ions.The ion associate was dissolved in a small volume of TMAH together with the MF. After being made up to 2 ml with water, the arsenic in the concentrate was determined by ETAAS in the presence of zirconyl nitrate as a chemical modifier. This method is very simple and rapid. The detection limit, defined as three times the standard deviation of the blank, was 0.04 µg l^–1. Inorganic matrix components in river waters, Na⁺, K⁺, Ca²⁺, Mg²⁺, SO₄^2–, NO₃^– and silicate at high concentrations did not interfere with the determination. Trace components, phosphate at 0.3 mg l^–1, dodecyl sulfate at 14 mg l^–1 and aluminium at 5 mg l^–1, also did not interfere with the determination. The proposed method was applied to the analysis of river water samples.