The implementation of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to measure six folate vitamers in serum samples allows a more individual and accurate measurement than the commonly used immunoassays. In the described method, serum samples undergo solid phase extraction followed by liquid chromatography coupled with electrospray ionization tandem mass spectrometry with a run time of 3.5 min. Recovery is 95 % for the most important folate metabolite, 5-methyltetrahydrofolate (MTHF), and greater than 78 % for other minor folate forms. The limit of detection ranges from 0.2 to 0.4 nmol/L with a intra-batch imprecision of less than 7 % for all analytes and calibration ranges of 1-100 nmol/L for MTHF and 0.5-20 nmol/L for the minor folate forms, with greater than 0.99 R2 linearity.
Keywords: 5-Methyltetrahydrofolate; Folate; Folic acid; LC-MS/MS; Solid phase extraction.