Improved Reverse Phase Liquid Chromatography Method for Iodine Value of Oils

Iodine value is an essential parameter for assessing the composition and quality of oils. A commonly used method for iodine value determination is the Wijs method. Recently, the HPLC method for assay of iodine monochloride via iodination of 2-chloroaniline with iodine monochloride has been reported. This study presents an approach for iodine value determination by HPLC via quantification of the unreacted iodine monochloride after reaction with oil samples, similar to the back titration approach in the Wijs method. Chromatographic conditions consist of gradient elution using water and acetonitrile on the C18 column with a detection wavelength of 304 nm. Oleic acid, with a known iodine value (83-103 gI/100 g), was used as a method development and validation reference compound. The method was validated as per International Conference on Harmonization guidelines and was accurate (98-102%), robust, and linear (r2 = 0.999) for oleic acid ranging from 5 to 20 mg. The repeatability and intermediate precision were within 1%. The validated method was applied for the iodine value determination of 10 cold-pressed oils. Thus, an HPLC method is developed, which offers minimal sample requirements, high accuracy, less manual intervention, and precision for the iodine value determination of oils.