Spectrophotometric Determination of Nitrate in Vegetables Using Phenol

A rapid and sensitive spectrophotometric method for the determination of nitrate in vegetables is described. The method is based on the measurement of the absorbance of yellow sodium nitrophenoxide formed via the reaction of phenol with the vegetable-based nitrate in presence of sulphuric acid. The analytical concentration of the acid has marked effect on the nitrate determined. The colour development was rapid and remained stable overnight. Analysis of six vegetable samples containing nitrate gave satisfactory mean recoveries of 76 to 123% in 18 determinations. The proposed method is reproducible and sensitive to lower level concentrations.