Short-chain carboxylic acids are commonly formed in the oxidation of vegetable oils, long carbon-chain fatty acids and biodiesel. The formation of short-chain (up to six carbons) carboxylic acids during induced oxidation in the Rancimat procedure for oleic acid (OA), linoleic acid (LA), linolenic acid (LnA), soybean oil (SO), methyl biodiesel from soybean oil (MBSO) and ethyl biodiesel from soybean oil (EBSO) was studied. Samples of OA, LA and LnA were submitted to oxidation, and the short-chain carboxylic acids formed were identified in their anionic forms using ion chromatography (IC). Formate, acetate, valerate and hexanoate were identified in the OA and LA samples. For the LnA sample formate, acetate, valerate, propionate and butyrate were found. For the MBSO, EBSO and SO, formate, acetate, propionate, valerate and hexanoate were identified. The rate of formation of formic acid was highest for each sample. The quantitative analysis of short-chain carboxylic acids present in lipid samples can help in determining product age, degree of oxidation, oxidative stability and corrosiveness. (C) 2017 Elsevier Ltd. All rights reserved.