SPECTROPHOTOMETRIC DETERMINATION OF TRACE OXALIC ACID WITH ZIRCONIUM(IV)-DIBROMOCHLOROARSENAZO COMPLEX

Abstract

Based on the property that oxalic acid has the effect on the replacement of dibromochloroarsenazo in zirconium(IV)-dibromochloroarsenazo complex to produce hyperchromic effects in 1.26 M hydrochloric acid medium, a novel method for the determination of trace oxalic acid by spectrophotometry was developed. The concentration of oxalic acid is linearly related to the absorbance at 500 nm. Beer's law is obeyed over the range of 5.0 x 10^-5 - 3.0 x 10^-4 M for oxalic acid. The apparent molar absorptivity of the determination of oxalic acid is ε500 nm = 1.52 × 10³ M^-1•cm^-1 with a correlation coefficient of 0.9994. The detection limit of the present method is 1.73 mg.L^-1 of oxalic acid. The method was used in the determination of trace amounts of oxalic acid in a few of kinds of tea leaves with satisfactory results.
KEY WORDS: Oxalic acid, Zirconium(IV)-dibromochloroarsenazo, Spectrophotometry

Bull. Chem. Soc. Ethiop. 2007, 21(2), 297-301.