Measurement of deuterium incorporation into fatty acids by gas chromatography/isotope ratio mass spectrometry

✍ Scribed by C. M. Scrimgeour; I. S. Begley; M. L. Thomason

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 47 KB
• Volume: 13
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(19990228)13:4<271::aid-rcm468>3.0.co;2-6

✦ Synopsis

A continuous-flow pyrolysis interface for gas chromatography/isotope ratio mass spectrometry (GC/IRMS) has been developed for 2 H analysis of individual organic compounds. Pyrolysis of gas chromatographically separated fatty acid methyl esters is performed at 1200 °C in an unpacked alumina tube to convert nanomole quantities of individual compounds to H 2 . Hydrogen is separated from other gaseous pyrolysis products on a solid-phase capillary column prior to its entering the mass spectrometer. Use of an isotope ratio mass spectrometer with high mass dispersion ensures 2 H 1 H: 1 H 1 H ratio measurement is accurately made in the presence of a large excess of helium carrier gas.

The technique has been applied to the measurement of lipid synthesis in humans, using deuterium oxide (D 2 O) incorporation into fatty acids. Using safe body water deuterium enrichments (`0.5%) the labelled fatty acids are unlikely to contain more than one deuterium per molecule, and show similar chromatographic behaviour to natural abundance samples. Following overnight incorporation of D 2 O, plateau palmitate enrichments were measured by GC/IRMS with a relative standard deviation (RSD) of $0.5%. This compares favourably with GC/MS measurements for which an RSD of 5 to 10% would be expected for similar samples. Compared to off-line sample conversion and IRMS, the current approach is much less laborious and gives information on individual fatty acids rather than the mixed triacylglycerols.