Reference standard for cholesterol evaluation in serum obtained by isotope dilution mass spectrometry
For the analysis by isotopic dilution, a sample containing the analyte to he measured is mixed with a known amount of the same analyte isotopically labelled, By gaschromatography-mass spectrometry (GC-MS), that allows to discriminate the labelled and the unlabelled compound on the basis of their molecular weight, it is possible to determine the intensity ratio of the two isotopes. The use as internal reference of the labelled analyte, that exhibits chemical-physical properties identical to the natural isotope, allows to not take into account the recoveries obtained from the different analytical steps, and the variability of the instrumental response, because the ratio between the two isotopic species remains unchanged during the overall analytical procedure. The analyte concentration is calculated on the basis of the volume of the specimen, the known amount of labelled analyte added, and the intensity ratio of specific ions of the two isotopes determined by GC-MS.
KeywordsCholesterol Concentration Isotope Dilution Mass Spectrometry Isotopic Species Label Cholesterol Unlabelled Compound
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