Determination and evaluation of EPA and DHA ethyl esters in fish oils using the TMAH transesterification method

A simple and dependable technique, known as THAM method, has been developed to detect and measure ethyl eicosapentaenoate (EE-EPA) and ethyl docosahexaenoate (EE-DHA) in encapsulated fish oils. This technique involves using tetramethylammonium hydroxide (TMAH) as a catalyst, followed by analysis using gas chromatography equipped with a flame ionization detector. Recoveries of EE-EPA and EE-DHA spiked between 5 mg/g and 20 mg/g were found to be between 90.8% and 95.2%, with coefficients of variation ranging from 0.2% to 2.5%, demonstrating the accuracy and precision of the technique. Additionally, its limitation of quantitation of EE-EPA and EE-DHA in fish oil samples was 0.2%. When compared with the direct injection method, the TMAH method yielded relative percent differences of no more than 3.8% in the amounts of ethyl esters of EPA and DHA in fish oil, while preventing contamination and maintaining its performance over time. Furthermore, when compared the total amounts of EPA and DHA with the boron trifluoride method, the relative percent differences were no more than 4.7% by the TMAH method. The advantages of using the TMAH method in distinguishing the ester forms of EPA and DHA and determining the total content of fatty acids in fish oils, which can provide an auxiliary check for evaluating the compliance of applications with the regulation related to the purity and form of EPA and DHA.