High accuracy analysis of glucose in human serum by isotope dilution liquid chromatography-tandem mass spectrometry.

Background: An isotope dilution mass spectrometry (IDMS) technique has been developed for high accuracy analysis of glucose in human serum. Currently, all the IDMS methods for glucose analysis are based on gas chromatography-mass spectrometry (GC-MS). In this study, isotope dilution liquid chromatography-tandem mass spectrometry (ID LC-MS/MS) was investigated.

Methods: NIST SRM 965b glucose in frozen human serum was analyzed by linear regression IDMS based on both LC-MS/MS and GC-MS. Serum samples were spiked with isotope labeled glucose and deproteinized by acetonitrile. For LC-MS/MS measurement, the supernate was injected directly after filtration and dilution. For GC-MS measurement, the supernate was evaporated to dryness and went through a two-step derivatization before injection.

Results: All measurements had good precision with CVs of <1%. Results from GC-MS agreed very well with results from LC-MS/MS, with a difference of <0.7%. The final reporting values in this study, based solely on LC-MS/MS, were within the certified ranges. The relative expanded uncertainties were within the range of 1.37% to 1.69% for the 4 levels of glucose, which were comparable with uncertainties from the certificate.

Conclusions: The IDMS method based on LC-MS/MS is precise and accurate. It does not require lengthy derivatization steps and thus, greatly simplifies the sample preparation procedure.