Determination of 5-methyltetrahydrofolic acid and folic acid in citrus juices using stable isotope dilution - Mass spectrometry

Paul M. Thomas, Vincent P. Flanagan, Robert J. Pawlosky*

*Corresponding author for this work

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

A stable isotope liquid chromatography - mass spectrometry (LC-MS) method was developed for the quantitative determination of 5-methyltetrahydrofolic acid (5 -MTHFA) and folic acid in a variety of commercial citrus juices. Folates were extracted from juices, and the polyglutamyl side chain of 5-MTHFA was cleaved to the monoglutamate form using rat plasma conjugase. The folates were purified on a Bond-Elut column and analyzed by LC-MS with electrospray ionization. The analytes were quantified using the 13C5 analogues of 5-MTHFA and folic acid as internal standards. The relative standard error of the method was 3.35% based on replicate analyses (n = 4). This method was then applied to the determination of 5-MTHFA and folic acid in a variety of citrus juices obtained from local supermarkets. It was observed that although both "store" brands and "national" brands of fresh (nonfrozen) juices contained similar concentrations of 5-MTHFA, the "store" brands of fresh juices had on average > 5-fold the amount of folic acid compared to the "national" brands. In addition, the "total" folate concentrations were generally below values listed on the food label.

Original languageEnglish (US)
Pages (from-to)1293-1296
Number of pages4
JournalJournal of Agricultural and Food Chemistry
Volume51
Issue number5
DOIs
StatePublished - Feb 26 2003

Keywords

  • 5-Methyltetrahydrofolic acid
  • Citrus
  • Electrospray ionization
  • Folic acid
  • Isotope dilution
  • Mass spectrometry

ASJC Scopus subject areas

  • Chemistry(all)
  • Agricultural and Biological Sciences(all)

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