Spectrophotometric Determination of Oxalate with Th(IV) and Arsenazo І Complex in Plants

A spectrophotometric technique using the Th(IV) complex with Arsenazo I was successfully applied to the determination of oxalate content in sorrel and spinach leaves without prior separation of matrix components. The determined linear range was 3.2–20 μmol·L-1 with the detection limit of 1 μmol·L-1. The method is characterized by satisfactory accuracy and is suitable for the analysis of plant material with the analyte content expectedly higher than the content of sulfates and phosphates. The mean content of oxalate in fresh sorrel leaves from the Kyiv marketplace was found to be 407±2 mg·g-1 for total oxalate content and 285±21 mg·100 g-1 for soluble one; from private household – 315±17 mg·100 g-1 and 245±4 mg·100 g-1 for total and soluble oxalate respectively. Quick-frozen spinach leaves were found to have the lowest oxalate content: 147±18 mg·100 g-1 and 110±19 mg·100 g-1 for total and soluble oxalate, respectively. The recovery coefficient calculated using the standard addition method was 81÷109%.