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.

U radu je prikazan jednostavan i efikasan metod za razdvajanje i određivanje dimetilarsenata, DMAs(V). Za izdvajanja DMAs(V) korišćena je hibridna smola modifikovana gvožđe-oksidom (HY). Za određivanje koncentracija arsena primenjena je metoda masene spektrometrije sa indukovano spregnutom plazmom (ICP-MS). Kvantitativno odvajanje DMAs(V) od svih vrsta arsena prisutnih u prirodnim vodam ostvareno je primenom HY smole uz kontrolu pH vrednosti. Pri pH vrednosti vode od 7,00 sve vrste arsena u vodi se kvantitativno vezuju za HY smolu izuzev DMAs(V). Kapacitet HY smole je izračunat na osnovu određivanja tačke proboja u protočnom sistemu, HY smola veže više od 4150 μg g-1 As(III), 3500 μg g-1 As(V) i 1500 μg g-1 MMAs(V). Kapacitet smole je visok i postojan i u prisustvu jona koji su prirodni sastojci vode. U efluentu je određena koncentracija DMAs(V) primenom ICP-MS. Predloženi metod je uspostavljen i potvrđen primenom standardnih analitičkih postupaka, analizom sertifikovanog referentnog materijala i analizom uzoraka uz primenu spoljašnjeg standarda i standardnog dodatka. Granica određivanja bila je 0,03 μg L-1, a relativna standardna devijacija (RSD) u opsegu između 1,1-7,50 %.