Spectrophotometric Determination of Trace Amounts of Arsenic In Sediment, Flyash and Water Samples

A simple, rapid, cost-effective spectrophotometric method is developed to determine arsenic in ppm levels. The present study is based on the reaction of arsenate with acidified molybdate and vanadate to form a molybdovanadoarsenate complex. The heteropoly acid complex formed interacts with cationic dye, Rhodamine B resulting in pinkcoloured ion-pair complex whose absorbance is measured at 590 nm. The colour developed is instantaneous and is stabilized with polyvinyl alcohol. Beer’s law is obeyed up to 0-0.24 μg mL The molar absorptivity, Sandell’s sensitivity, detection limit and limit of quantification (LOQ) are 1.653 × 10 L molcm, 4.532 × 10 μgcm, 0.00916 μg mL and 0.02785 μg mL respectively. The composition of ion-pair complex formed is found to be arsenic: molybdenum: vanadium: Rhodamine B is 1:11:1:4 by mole-ratio method. The proposed method is highly sensitive for arsenic with phosphate alone interferes which is eliminated by reducing arsenate to arsine. The method is useful in determining arsenic at low concentrations in sediment, fly ash and water samples.