An efficient method for determining the acid value in edible oils by solvent-assisted headspace gas chromatography

This work reports a simple and efficient method for the determination of the acid value in edible oils by solvent-assisted and reaction-based headspace gas chromatography (HS-GC). The neutralization reaction between the fatty acids in oils and bicarbonate in an ethanol (80%) aqueous solution was performed in a closed headspace sample vial, from which the carbon dioxide generated from the reaction was detected by HS-GC. It was found that the addition of ethanol can effectively improve the reaction of fatty acids in oils with bicarbonate, conducted at 75 degrees C for 30 min. The results showed that the relative standard deviation (RSD) of the present method in the repeatability test was less than 1.63%, and the limit of quantitation (LOQ) was about 0.039 mg KOH per g. The present method was validated by a standard reference method on a set of oil samples from the market, in which the relative differences of the AV data obtained by these two methods were within 5.52%. The present method is simple, efficient, and accurate, and it is suitable for determining the AV in oils in a wide variety of applications.