Solid Phase Extraction of Arsenic by Sorption on Naphthalene-Methyltrioctyl
Ammonium Chloride and Spectrophotometric DeterminationMohsen 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 1–8 ng mL–1 in the initial
solution with r=0.999 (n=6). The relative standard deviation for 15 replicate
measurements of 6.0 ng mL–1 of arsenic was 1.3% and the 3s detection
limit was 0.067 ng mL–1. 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