Determination of p-Aminobenzoic Acid in Feeds

Collaborative studies were conducted on a revised method for p-aminobenzoic acid (PABA) in feeds. PABA is diazotized and coupled with N-1-naphthylethylenediamine dihydrochloride to form a red complex that provides both a qualitative test and a spectrophotometric assay. The PABA is extracted with a 10% hydrochloric acid solution and the alkaline hydrolysis step is eliminated. Results were close to the labeled drug content, although the aged feed evidenced drug instability. The revised method is recommended for adoption as official, first action.