Quantitation of Underivatized Omega-3 and Omega-6 Fatty Acids in Foods by HPLC and Charged Aerosol Detection
The omega fatty acids are a group of compounds that include essential n-3 and n-6, and nonessential n-9 analytes. The omega-3 fatty acids, which also include eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA], are required for normal growth and health. Although both omega-3 and -6 fatty acids can give rise to eicosanoid-signaling molecules (prostaglandins, prostacyclins, thromboxanes and leukotrienes), the omega-6 eicosanoids are generally pro-inflammatory and may play a role in disease. It appears that the amounts and balance of omega fatty acids in a person's diet affect their eicosanoid-controlled functions. A proper balance of omega fatty acids in the diet is important. Traditionally, omega fatty acids are measured using gas chromatography (GC). For foods, analytes are extracted from the samples prior to hydrolysis to release the fatty acids from their triglycerides, and then converted to their volatile methyl-esters prior to analysis by GC. Regardless, this approach is tedious, time-consuming, and the high temperatures can affect polyunsaturated fatty acid stability. Charged aerosol detection (CAD), a universal mass-based approach, is sensitive, has a wide dynamic range, and has a major advantage in that all nonvolatile analytes give similar response independent of chemical structure. No derivatization is required, and unlike UV detection, the analyte does not need to contain a chromophore. Presented here is a simple and direct HPLC-CAD method that can be used to measure omega-3, -6, and -9 fatty acids in traditional and commercially produced meat, fish, and oils, as well as over-the-counter supplements.