A Rapid Spectrophotometric Determination of Thorium with DBCArsenazo as a Chromogenic Reagent

Abstract

A simple, rapid and sensitive spectrophotometric method   for the determination of trace amount of thorium(IV) has been   developed using DBC-arsenazo (DBC-ASA) as a chromogenic   reagent in a 1.0 mol L^-1 hydrochloric acid solution. Absorbance   was measured in 1 cm cell and the complex has the   maximum peak of absorption at 622 nm. The complex of   thorium thus formed, is stable for 1 h with constant absorbance.   Beer's law is obeyed in the range 0-0.60 μg mL^-1 of   thorium concentration with an apparent molar absorptivity at   ε_{622 nm} = 7.15 × 10⁴ L mol^-1 cm^-1 at 25 ºC. The linear regression   equation of the method is A = 0.032C-0.004 [C: μg Th(IV)/   10 mL], the correlation coefficient γ = 0.9991. The stoichiometric   composition of the Th-(DBC-ASA) complex is 1:2. A   large excess of cations and anions do not interfere with the   determination of thorium. The proposed method was directly   applied to the determination of thorium in hairtail and dried   shrimps samples with satisfactory results. The relative standard   deviation of nine replicate determinations and the recovery were   over the range of 1.45-2.95 and 99.3-101.1 %, respectively.