Spectrophotometric determination of oxalic acid using zirconium(IV)-(p-acetylarsenazo) system

A new spectrophotometric method for determination of oxalic acid has been developed. It is based on the property that in 0.40 mol L-1 HCl solution oxalic acid forms complexes with zirconium by replacing p-acetylarsenazo in zirconium-(p-acetylarsenazo) complex. The formed complex makes the absorbance of the solution increase. Over a specified range, the measured absorbance was proportional to the concentration of oxalic acid in the range of 3.0 x 10(-5)-6.0 x 10(-4) mol L-1, according to Beer's law. The apparent molar absorptivity was epsilon(540nm) = 1.02 x 10(3) Lmol(-1) cm(-1). The detection limit of the method was 2.5 x 10(-5) mol L-1. The proposed method was satisfactorily applied to the determination of trace amount of oxalic acid in spinach and strawberry samples.