Determination of As5+. The residual aqueous fractions obtained from step 2, added 1 ml of HBr and 15 mg hydrazine sulphate for reduction of As5+ to As3+ (Korenovska & Suhaj, 2005). After subjecting to ultrasonic bath for 5 min at 80 C, the content of the flasks was treated with 10 ml chloroform and placed in ultrasonic bath for 1 min (twicely). The chloroform phase was taken in separating funnel and added 10 ml of 1 M HCl to extract As+5 and determined by ETAAS.