Quantitation of monosaccharide isotopic enrichment in physiologic fluids by electron ionization or negative chemical ionization GC/MS using di-O-isopropylidene derivatives

Anal Chem. 1999 Oct 15;71(20):4734-9. doi: 10.1021/ac990724x.


The aldonitrile pentaacetate and other derivatives lack ions in the electron ionization (EI) spectra possessing an intact hexose structure and thus must be analyzed by chemical ionization GC/MS in order to study multiple isotopomers. We report methods for quantitation of hexose di-O-isopropylidene acetate (IPAc) or pentafluorobenzoyl (PFBz) esters. These were prepared in a two-step procedure using inexpensive reagents that do not adversely impact the isotopomer structure of the sugar. The acetate derivative possesses an abundant [M - CH3] ion in the EI spectrum which is suitable for quantitative analysis of isotopomers. The negative chemical ionization (NCI) spectrum of the corresponding pentafluorobenzoyl derivative has a dominant molecular anion. Moreover, the PFBz derivative is about 100-fold more sensitive than the acetate, which offers some advantages for analysis of minor hexoses found in plasma. Isotopic calibration curves of [U-13C]glucose are linear over the 0.1-60% tracer/tracee range tested. The useful range for isotopic tracer studies is 25-2500 pmol for EI analysis of the acetate derivative and 0.1-55 pmol for NCI analysis of PFBz derivative (sample amount injected). For most studies where sample size is not limited, EI-GC/MS analysis of the IPAc derivative is preferred. NCI-GC/MS analysis is reserved when sample size is limiting or when studies involve hexoses other than glucose that are normally present at low concentration.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alkenes / analysis*
  • Alkenes / blood
  • Blood Glucose / analysis
  • Gas Chromatography-Mass Spectrometry
  • Humans
  • Indicators and Reagents
  • Monosaccharides / analysis*
  • Monosaccharides / blood


  • Alkenes
  • Blood Glucose
  • Indicators and Reagents
  • Monosaccharides