Use of carbon nanotubes and electrothermal atomic absorption spectrometry for the speciation of very low amounts of arsenic and antimony in waters

A procedure for the determination of inorganic arsenic (III, V) and antimony (III, V) in water samples by using a miniaturized solid-phase extraction with carbon nanotubes followed by electrothermal atomic absorption measurement is proposed. The trivalent species are first complexed with ammonium pyrrolidinedithiocarbamate, next retained in a mini-column containing nanotubes and then eluted by means of a plug of an ammonia solution. The atomizer is impregnated with a tungsten salt which acts as an effective chemical modifier during the heating cycle. Total inorganic arsenic and antimony are determined after the reduction of the pentavalent forms with an ammonium iodide solution. Pentavalent arsenic and antimony are calculated by difference. When using 50 mL sample solutions, the limits of detection are 0.02 and 0.05 μg L−1 for As and Sb, respectively, and the enrichment factor is 250. The relative standard deviations calculated for five determinations at the 1 μg L−1 level are below 4%.