Spectrophotometric Reaction Rate Method for Determination of Oxalic Acid in Food Based on Its Enhancing Effect on the Oxidation of Pyrocathecol Violet by Dichromate

ABSTRACT

A simple kinetic spectrophotometric method for the determination of oxalic acid has been described, based on its catalytic effect on the oxidation of pyrocathecol violet (PCV) with potassium dichromate in acidic media. The reaction was monitored photometrically by measuring the decrease in absorbance of PCV at 450 nm. The influence of acid, PCV concentration, dichromate concentration, and temperature were studied and optimized completely. Under the optimum condition, a calibration graph from 0.08 to 1.3 µg/mL of oxalic acid with a detection limit of 0.07 µg/mL was obtained. The relative standard deviation for ten replicate measurement of 0.8 µg/mL oxalic acid is 0.8%. The proposed method is fast and simple. The applicability of the method was demonstrated by the determination of oxalic acid in wastewater, spinach, and mushroom samples.

Keywords:

• Oxalic acid
• Catalytic
• Pyrocathecol violet
• Spectrophotometry

ACKNOWLEDGMENT

The authors thank the Center of Excellency in Chemistry (IUT) for supporting of this work.

Notes

^aMaximum concentration of substance tested.