Utilization of hydrosilated silica-based stationary phases for separation of antioxidants

Abstract

We studied the influence of mobile phase composition on the retention of phenolic acids and flavonoid compounds on five different hydrosilated silica-based stationary phases in buffered aqueous acetonitrile. Cogent UDC cholesterolTM, Cogent bidentate C18TM and Cogent Phenyl hydrideTM columns show significant dual reversed-phase/normal-phase retention behaviour, while Cogent Diamond hydrideTM and Cogent Silica-CTM columns provide very low retention in the reversed-phase mode. The effect of the aqueous acetate buffer concentration on retention factors of phenolic acids and flavonoid compounds over the full mobile phase composition range, including both aqueous normal-phase (ANP) and reversed-phase (RP) mechanisms, can be described by a four-parameter equation for dual-retention mechanism. At increasing temperature, the retention factors and peak widths decrease in the aqueous normal-phase range. In agreement with van’t Hoff model, linear ln k versus 1/T plots were observed, showing a single retention mechanism. From among the stationary phases tested, Cogent UDC cholesterolTM column has high temperature stability (up to 100 °C) and provides the most selective and efficient separations of flavones in the ANP mode and Cogent Diamond hydrideTM is the most selective and effective for separation of phenolic acids.