We describe a reliable method for the simultaneous determination of isotopic enrichments of [1-13C]homocysteine, [1-13C]methionine and [2H3-methyl-1-13C]methionine in human plasma. Accurate [1-13C]homocysteine calibration standards were prepared by chemical conversion via thiolactonisation of [1-13C]methionine standards. Based upon anion-exchange chromatography, (di)acetyl-3,5-bis-trifluoromethylbenzyl derivatives, preparation of accurate calibration curves and gas chromatography-negative chemical ionization mass spectrometry, isotopic enrichments in human plasma could be determined with TTR (%) <±0.2% (N=3) for [1-13C]homocysteine (enrichment range 0-8%), [1-13C]methionine (enrichment range 0-3%) and [2H3-methyl-1-13C]methionine (enrichment range 0-12%). The method was applied in a [2H3-methyl-1-13C]methionine tracer infusion study in a biological model. Copyright (C) 2000 Elsevier Science B.V.
Kulik, W., Kok, R. M., De Meer, K., & Jakobs, C. (2000). Determination of isotopic enrichments of [1-13C]homocysteine, [1-13C]methionine and [2H3-methyl-1-13C]methionine in human plasma by gas chromatography-negative chemical ionization mass spectrometry. Journal of Chromatography B: Biomedical Sciences and Applications, 738(1), 99–105. https://doi.org/10.1016/S0378-4347(99)00504-6