Spectrophotometric Determination of p-Aminobenzoic acid Results from Procaine Drug Using 2, 6-Dihydroxybenzoic acid as Coupling Agent


A spectrophotometric method for the trace determination of p-aminobenzoic acid (PABA) has been proposed. The method is based on the coupling of diazotised PABA with 2,6-dihydroxybenzoic acid in basic medium to form a yellow,stable and water soluble azo-dye which shows a maximum absorption at 438 nm with a molar absorptivity of 5.2745 104 l.mol-1.cm-1 and obeys Beer’s law in the concentration range 10-100 g of PABA in a final volume of 25ml i.e., 0.4-4 ppm with a relative error of +0.11 to -3.71 % and a relative standard deviation of 2.11 to 5.13 % depending on concentration level. The present method has been applied successfully to the determination of PABA which results from hydrolysis of procaine drug.