PH-Metric Determination of the Acid Value of Vegetable Oils without Titration

Abstract

The acid value (AV) of vegetable oils is determined without titration by using a new reagent consisting of triethanolamine in a solution of water and isopropyl alcohol. When the oil sample is mixed with the reagent in the pH-metric cell, free fatty acids from the sample are extracted into the reagent (3-4 min). The initial pH, called conditional pH′1, is measured, a standard acid (HCl) is added, and the final pH, pH′2, is measured. AV is calculated from the difference between pH′1 and pH′2. The method is applicable for quality control of vegetable oils during their production, trade, and use.