An integrated electrocatalytic nESI-MS platform for quantification of fatty acid isomers directly from untreated biofluids†
Positional isomers of alkenes are frequently transparent to the mass spectrometer and it is difficult to provide convincing data to support their presence. This work focuses on the development of a new reactive nano-electrospray ionization (nESI) platform that utilizes non-inert metal electrodes (e.g., Ir and Ru) for rapid detection of fatty acids by mass spectrometry (MS), with concomitant localization of the CC bond to differentiate fatty acid isomers. During the electrospray process, the electrical energy (direct current voltage) is harnessed for in situ oxide formation on the electrode surface via electro-oxidation. The as-formed surface oxides are found to facilitate in situ epoxide formation at the CC bond position and the products are analyzed by MS in real-time. This phenomenon has been applied to analyze isomers of unsaturated fatty acids from complex serum samples, without pre-treatment.