HPLC retention behavior on hydride-based stationary phases

Area of Science:

• Chromatography
• Separation Science
• Analytical Chemistry

Background:

• Silica hydride stationary phases offer unique surface chemistry.
• Understanding retention mechanisms is crucial for method development in pharmaceutical analysis.

Purpose of the Study:

• To investigate retention mechanisms of cholesterol and bidentate C18 stationary phases on a silica hydride surface.
• To elucidate how solute properties (log P, pKa) and mobile phase composition influence retention.
• To demonstrate the potential for reversed-phase (RP), aqueous normal phase (ANP), and dual retention mechanisms.

Main Methods:

• Utilized two distinct stationary phases: cholesterol and bidentate C18, both bonded to a silica hydride surface.
• Employed a range of pharmaceutically relevant test solutes with varying hydrophilicity/hydrophobicity (log P, pKa).
• Investigated mobile phases comprising acidified water/methanol or water/acetonitrile (ACN) mixtures, focusing on high organic content compositions.

Main Results:

• Demonstrated that silica hydride-based stationary phases exhibit multiple retention mechanisms.
• Observed retention behavior consistent with RP, ANP, and dual retention modes depending on solute and mobile phase conditions.
• Highlighted that retention can increase in high organic mobile phases, indicative of ANP operation.

Conclusions:

• Silica hydride stationary phases, including cholesterol and bidentate C18, provide versatile chromatographic performance.
• These phases can operate in RP, ANP, and dual retention modes, offering flexibility for analyzing diverse pharmaceutical compounds.
• The ability to operate in ANP mode, particularly at high organic content, expands their applicability in separation science.