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.
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.
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.