2.3. HPLC analysis of acyl‐CoA fatty acids

Brain tissues were ground to a powder and 6 mg extracted27 for reverse‐phase LC (Agilent 1200 LC system; Gemini C18 column, 2 mm inner diameter, 150 mm with 5 mm particles) with electrospray ionisation tandem mass spectrometry (multi reaction monitoring, MRM) on a QTRAP 4000 (SCIEX) instrument in positive ion mode. LC‐MS/MS MRM analysis followed the methods previously described.28 A total of 68 acyl‐CoA fatty acids (14:0 to 34:6) were tracked using individual MRM mass pairs. For identification and calibration, standard acyl‐CoA esters with acyl chain lengths from C14 to C20 were purchased from Sigma as free acids or lithium salts.