Quantification of vitamin B6 vitamers in human cerebrospinal fluid by ultra performance liquid chromatography–tandem mass spectrometry Original Research Article

Since vitamin B6 is essential for normal functioning of the central nervous system, there is growing need for sensitive analysis of B6 vitamers in cerebrospinal fluid (CSF). This manuscript describes the development and validation of a rapid, sensitive and accurate method for quantification of the vitamin B6 vitamers pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), pyridoxic acid (PA), pyridoxal 5′-phosphate (PLP), pyridoxamine 5′-phosphate (PMP) and pyridoxine 5′-phosphate (PNP) in human CSF. The method is based on ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) with a simple sample preparation procedure of protein precipitation using 50 g L−1 trichloroacetic acid containing stable isotope labeled internal standards: PL-D3 for PL and PM, PN-13C4 for PN, PA-D2 for PA and PLP-D3 for the phosphorylated vitamers. B6 vitamers were separated (Acquity HSS-T3 UPLC column) with a buffer containing acetic acid, heptafluorobutyric acid and acetonitrile. Positive electrospray ionization was used to monitor transitions m/z 168.1 → 150.1 (PL), 169.1 → 134.1 (PM), 170.1 → 134.1 (PN), 184.1 → 148.1 (PA), 248.1 → 150.1 (PLP), 249.1 → 232.1 (PMP) and 250.1 → 134.1 (PNP).