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

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