ABSTRACT
Isotope dilution MS was used to verify the absence of formation of potential artifacts by the method itself. To this end, different types of samples representing different stages in the whole analytical procedure were spiked with deuterated cholesterol. GC-MS was performed after the various stages of sample preparation. Figure 17 shows the GC-MS chromatogram obtained of a sample subjected to the entire protocol. Note that no new oxidation products have been formed; the 7-keto-∆7-cholesterol was already present in the ∆7-cholesterol as purchased from Sigma. The most abundant oxidation product normally formed from cholesterol, 7-OH cholesterol, was not increased as a result of the sample preparation method.
