Dexamethasone derivatization

Tablets HPLC Derivatize with homochiral reagent Silica n-Hexane-CHjC l -IPA (100 100 4) 240 nm Resolved epimers along with dexamethasone...

The analysis of steroids is a challenging task. GC-MS has frequently been applied, but requires analyte derivatization [1]. Therefore, over the years most LC-MS interfaces have been tested or applied in the analysis of steroids. As early as 1981, Henion [2] demonstrated the analysis of dexamethasone and cortisone with micro-LC coupled to a capillary-inlet interface. Van der Greef et al. [3] described the quantitation of progesterone in serum using isotope dilution MS in anunonium Cl mode using the moving-belt interface. Henion and coworkers [4] described... 

Chen, S.-H. Wu, S.-M. Wu, H.-L. Stereochemical analysis of betamethasone and dexamethasone by derivatization and high-performance liquid chromatography. J.Chromatogr., 1992, 595, 203-208... 

Special attention is drawn to the analysis of isomers with GC-MS. An illustrative example is the analysis of dexamethasone and betamethasone. The analytes are identical with only one difference in the orientation of the 16-methyl group (a resp. P). Usually in reversed-phase HPLC systems, the retention times are almost Identical. Underlvatized or after derivatization to (tetra-)TMS derivatives, the resulting mass spectra are virtually indistinguishable. Using the oxidation procedure as described by Courtheyn [46,47], the spectra are again almost identical (Fig. 3). However, a difference is seen between the ratio of the two oxidized isomers formed. Dexamethasone has a higher a to P ratio, whereas betamethasone shows a reversed ratio. If a mixture of dexamethasone and betamethasone is present, the difference in ratios cannot distinguish the analytes anymore. 

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