Methods and systems for measuring ascorbic acid

A method for determining an amount of ascorbic acid in a biological sample by tandem mass spectrometry, comprising:

• (a) generating a precursor fragment ion from ascorbic acid having a mass to charge ratio (m/z) of about 115 by in-source fragmentation prior to entry of the precursor fragment ion into a quadrupole of a tandem mass spectrometer;
• (b) generating a product ion of the precursor fragment ion by tandem mass spectrometry (MS/MS), wherein the product ion has a mass/charge ratio (m/z) of about 59;
• (c) detecting the amount of the product ion generated in (b);
• and
• (d) relating the detected product ion to the amount of the ascorbic acid in the biological sample.