A modified spectrophotometric procedure for the determination of pyruvic acid in onions using benzaldehyde derivatives

A modified spectrophotometric method for the analysis of pyruvic acid, a compound of agricultural and medical significant is described. The color formation reaction is based on the reaction of pyruvic acid with some benzaldehyde derivatives in an alkaline medium to produce products with yellow colors which exhibit maximum absorbance at 414–446 nm. The monitored spectrophotometric absorbance is evaluated and optimized with respect to various experimental conditions. For the selected benzaldehyde derivative (p–dimethylaminobenzaldehyde), Beer's law is obeyed over the concentration range 5–215 μg ml⁻¹ pyruvic acid. The developed analytical procedure shows a good reproducibility, the relative standard deviation RSD% (n=5) at a concentration level of 50 μg ml⁻¹ is 0.85% whereas the accuracy of the method is illustrated via the mean recovery of 98.8%. Applicability of the developed method was demonstrated by the determination of pyruvic acid in agricultural samples (onion) and the achieved results were compared with that obtained by reference spectrophotometric method. The statistical analysis (F–test) of these data showed that the results of both analytical methods compared favourably.