Separation and determination of dimethylarsenate in natural waters

Abstract

A simple and efficient method for the separation and determination of dimethylarsenate DMAs(V) was developed in this work. Two resins, a strong base anion exchange (SBAE) resin and iron-oxide coated hybrid (HY) resin were tested. By simple adjustment of the pH value of water to 7.00, DMAs(V) passed through the HY column without any changes, while all other arsenic species (inorganic arsenic and monomethylarsonate, MMAs(V)) were quantitatively bonded on the HY resin. The resin capacity was calculated according to the breakthrough point in a fixed bed flow system. At pH 7.00, the HY resin bonded more than 4150 μg g-1 of As(III), 3500 μg g-1 of As(V) and 1500 μg g-1 of MMAs(V). Arsenic adsorption behavior in the presence of impurities showed tolerance with the respect to potential interference of anions commonly found in natural water. DMAs(V) was determined in the effluent by inductively coupled plasma mass spectrometry (ICP-MS). The detection limit was 0.03 μg L-1 and the relative standard deviation (RSD) was between 1.1-7.5 %. The proposed method was established by application of standard procedures, i.e., using an external standard, certified reference material and by the standard addition method.