SEPARATION OF ARSENITE, ARSENATE AND DIMETHYLARSENIC ACID IN WATER BY SILICA-BASED COLUMNS FOR DETERMINATION BY ICP-OES

Abstract

A simple and low cost method was proposed for the separation and determination of three arsenic species (As(III), As(V) and dimethyl arsenic acid (DMA)) in water by solid phase extraction (SPE) followed by inductively coupled plasma-optical emission spectrometry (ICP-OES). Two types of columns including a strong anion exchange column and a silver chloride-silica-based column were used for the separation of arsenic species. The pH of solution, flow rate, eluent concentration and sample concentration were studied for assessing optimal conditions. At pH 9, inorganic arsenic species (As(III) and As(V)) were retained on the silver chloride-silica-based column while DMA was pass through the column. The strong anion exchange could adsorb As(V) at pH 7 and afterwards the adsorbed As(V) was eluted by 1 mol/L HCl. All obtained solutions were analyzed for arsenic concentration by ICP-OES. The concentration of As(III/V/DMA) was determined directly or calculated from the subtraction from the total arsenic concentration. Under the optimal conditions, the method detection limit, percent recovery and percent relative standard deviation of As(III), As(V) and DMA were in the range of 1.48-2.51 µg/L, 93.3-101.1 and 1.56-2.03, respectively. Moreover, the proposed method was successfully applied for the speciation of arsenic species in real industrial wastewater samples. The percent recovery and percent relative standard deviation of As(III), As(V) and DMA were in the range of 97.2-104.3 and 0.72-2.56, respectively