Rapid quantification of polar compounds in thermo-oxidized oils by HPTLC-densitometry

The level of polar compounds is a good indicator of oil quality and it is the basis of the international regulations limiting the use of degraded frying fats/oils for human consumption. According to ISO 8420:2002 standard, polar compound content is determined by adsorption chromatography extraction followed by gravimetric quantification. This simple and accurate method is time-consuming and considerable amounts of silica-gel and solvents are needed. This study aims at developing a fast and reliable alternative method for polar compound quantification in frying oils, using HPTLC-densitometry. This technique was tested for soybean, sunflower and peanut oils, heated at 180°C, and for frying oil samples. This technique proved to be fast, accurate and repeatable. Practical applications: The developed method is adequate for rapid screening of unknown oil samples, with respect to their level of polar compounds. Using HPTLC-densitometry to evaluate polar compound content in oils, the number of samples to be analyzed by the ISO standard method may be considerably reduced to those having values close to the maximum allowed. Thus, the proposed methodology allows for a reduction in time and chemicals used, with economic and environmental benefits. HPTLC-densitometry is an alternative technique to the standard method for polar compound quantification in heated/frying vegetable oils. The method developed is fast, accurate, and repeatable with economic and environmental benefits.