Determination of the Total Concentration of Halogen- and Sulfur-Organic Compounds in Vegetable Oils of Different Degrees of Purity—a New Approach to Assessing Their Safety

Abstract

A methodology is proposed for the highly selective, sensitive, and reliable determination of the total concentration of halogen and sulfur organic compounds in vegetable oils in the presence of inorganic salts, based on the direct high-temperature conversion of an oil sample in a stream of pure oxygen, absorption of inorganic salts in a reactor, absorption of the products of analyte conversion with deionized water to form F^–, Cl^–, Br^–, and S${\text{O}}_{4}^{{2 - }}$ anions, and their determination in the absorbate by ion chromatography. An increase in the reliability of the determination of F^–, Cl^–, and Br^– anions is provided by combining the registration of retention times in the direct determination of anions with an analysis of the flow of the same absorbate after the selective removal of F^–, Cl^–, and Br^– anions (together) using corresponding adsorption columns packed with cation exchangers R^–Al³⁺ (for F^–) and R^–Ag⁺ (for Cl^– and Br^–) (possibility of distortion of the determination result of these anions due to potentially coeluted components is excluded). Using the proposed methodology, the total concentration of halogen and sulfur organic compounds is determined in samples of vegetable oils of varying degrees of purity. It ranged from 2 × 10^–6 to 6.0 × 10^–2% (in terms of element), depending on the sample and element, at a sample volume of 1 μL. A possibility of increasing sample volume by up to 15 times and lowering the limits of detection to 10^–7% (in terms of element) is shown.