Determination of arsenic by inductively coupled plasma atomic emission spectrometry after pre-concentration on an acid-soluble membrane filter as arsenomolybdate in the presence of a quaternary ammonium salt

Abstract

A simple pre-concentration technique, based on collecting trace analytes on a membrane filter and dissolving the filter and the analytes in a suitable solvent, has been applied to the determination of arsenic in water by inductively coupled plasma atomic emission spectrometry. Arsenic, in the range 1–50 µg in a 100–500-ml sample, is collected on a nitrocellulose membrane filter as an ion associate of arsenomolybdate with tetrapentylammonium ion. The membrane filter and the arsenomolybdate are dissolved in a small volume of concentrated sulphuric acid, diluted to 2–10 ml and aspirated into the nebuliser. Arsenic is determined from the emission intensity at 228.812 nm. Moderate concentrations of silicate, phosphate and cadmium and high concentrations of sodium chloride do not interfere. Enrichment factors as high as 250 can be easily attained by the proposed pre-concentration technique. The detection limit, defined as three times the standard deviation of the blank, is 0.3 µg l^–1 with 250-fold pre-concentration.