PRACTICAL LIMITATIONS IN DETERMINING VEGETABLE OIL ACID VALUES BY A NOVEL PH-METRIC METHOD

A novel pH-metric method is described for the determination of acid va lues (AV) in vegetable oils without titration. The method is based on a reagent containing triethanolamine, isopropanol, and water to which an oil sample is added before measuring pH. Oil samples with AV in the range 0.006-0.707 mg KOH/g oil were prepared from commercial soybean oil by treatment with a strong-base anion exchanger in OH- form and ad dition of oleic acid. Compared to the standard titrimetric method, sig nificantly greater AV were obtained at less then 0.02 mg KOH/g oil. Th is was due to the influence of triethanolamine hydrolysis on the acid- base equilibrium in the mixture ''oil-reagent.'' Thus, the AV 0.02 mg KOH/g oil is accepted as the limit of quantitation. Because refined oi ls usually have AV of 0.05 mg KOH/g oil or more, this method should be suitable for practical oil analyses.