Solid Phase Extraction of Arsenic by Sorption on Naphthalene-Methyltrioctyl Ammonium Chloride and Spectrophotometric Determination

Mohsen Behpour,* Sayed Mehdi Ghoreishi, and Sakineh Salehi
Department of Chemistry, Faculty of Science, Kashan University, Kashan, IRAN. E-mail: M.Behpour@Kashanu.ac.ir

Abstract
A simple, sensitive, rapid and reliable preconcentration method has been developed for spectrophotometric determination of trace amounts of arsenic. Arsenic was retained on a minicolumn of adsorbent naphthalene, as an ion associate of arsenomolybdate and methyltrioctylammonium ions. The contents of column was dissolved in a small volume of N,N-dimethylformamide (DMF) having stannous chloride (SnCl2) as a solvent. To take advantage of the procedure the reagent concentration and reaction condition must be optimized.
Effects of different parameters such as molybdate percent, hydrochlorice acid concentration in aqueous solution, the flow rate of the sample solution through the minicolumn, selection of a suitable solvent to dissolve the adsorbent and also various salts and metal ions as interferences were investigated. Recording the variation in absorbance at a wavelength of 715 nm at room temperature completes the determination of arsenic concentration. The method allows determination of arsenic in the range of 18 ng mL1 in the initial solution with r=0.999 (n=6). The relative standard deviation for 15 replicate measurements of 6.0 ng mL1 of arsenic was 1.3% and the 3s detection limit was 0.067 ng mL1. The preconcentration factors of 100 and 167 could be achieved when using a 5 and 3 mL DMF for dissolving adsorbent, respectively. The optimized method was successfully applied to determination of arsenic in natural water, synthetic sample and fish. 

Keywords: Arsenic, solid phase, extraction, spectrophotometric determination