Separation Differences Among Phenyl Hydride, UDC Cholesterol and Bidentate C8 Stationary Phases for Stability Indicating Methods of Tetracyclines: Journal of Liquid Chromatography & Related Technologies.

Formulation extracts of tetracycline hydrochloride (HCl), minocycline hydrochloride (HCl), and doxycycline hyclate were degraded by strong acidic conditions and heating. Subsequently, components of the extracts were separated by Bidentate C8, Phenyl Hydride and Cholesterol (UDC) HPLC columns operating in the reverse phase mode. The Phenyl Hydride column was able to baseline separate minocycline from the observed degradant, while partial or total co-elution was observed with the other two columns using otherwise identical method conditions. For both the degraded tetracycline HCl and doxycycline hyclate extracts, the UDC column gave the best resolution for the critical pair. The findings suggest that the postulated secondary retention mechanisms of π-π interactions from the Phenyl Hydride and shape selectivity from the UDC can provide superior resolution for structurally similar analytes compared to hydrophobic interactions alone.