Each year over half a million deaths from coronary heart disease are estimated to be attributed to high trans-fatty acid (TFA) intake worldwide. TFA are the geometric isomers of naturally occurring cis-fatty acids and can be formed industrially via partial hydrogenation of vegetable oils or naturally in ruminant animals. Many positional and geometric fatty acid (FA) isomers have been reported in humans, but some may not be fully separated with current gas chromatography (GC) methods. This could lead to inaccurate results for certain fatty acids and incorrect interpretation of human exposure to TFA, creating the need for a new approach to assess TFA in humans. Silver ion chromatography has been widely used in the study of FA in oils and dairy products, but has seen limited application to human blood. We have developed a method using silver ion high-performance liquid chromatography (HPLC), with two columns in series, coupled to a diode array detector to evaluate the resolution of TFA isomers from regular FA in human plasma in conjunction with GC-Mass Spectrometry (MS). This approach allows us to fully separate TFA from their cis-FA isomers in biological samples, even in the C18:1 region where cis/trans overlap is common. Additionally, we achieved HPLC resolution of cis/trans and trans/cis isomers in the C18:2 region. With this method, we were able to identify 3 TFA not previously reported in human plasma, including C20:1n-9t and C22:1n-9t. Overall, with this approach we are able to separate and detect over 50 FA isomers in human plasma.
