This article from Issue 9 of the Analytix Reporter, produced by Merck, provides a simple, precise, and sensitive reversed-phase high performance liquid chromatography (RP-HPLC) gradient method for establishing traceability and total chromatographic analysis of dexamethasone.
The given experimental conditions follow the USP43-NF38 monograph method for dexamethasone assay and organic impurity profiling. Baseline-resolved peaks were obtained for dexamethasone, betamethasone, dexamethasone acetate, and desoximetasone within 20 minutes with a Titan™ C18 UHPLC column (10 cm x 2.1 mm, 1.9 µm particles). This column has the same phase, length, and ID like in the monograph, but the packing is based on monodisperse particles with a slightly larger average particle size (1.9 µm), than referenced in the monograph (1.7 µm). The method was validated following the guidelines in USP General Chapters <621>, <1225>, and <1226>. The use of lower sample concentrations was compensated by a larger injection volume (to maintain mass on column) to improve reproducibility. The chromatographic separation was achieved using a mixture of 3.4 g/L monobasic potassium phosphate solution (pH 3.0) and acetonitrile as the mobile phase with gradient elution and UV detection at 240 nm. Although, comparatively a shorter relative retention time (RRT) was observed for dexamethasone acetate and desoximetasone, both the compounds showed an excellent chromatographic resolution (Rs > 10). Under the applied conditions, system suitability requirements are met, and the method demonstrates good selectivity, reproducibility, sensitivity, and accuracy.
For full experimental conditions and chromatographic data, download the full article.
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