title: Characterization of a range of alkyl-bonded silica HPLC stationary phases:  correlation of quantitative surface analysis data with the retention behavior of neutral, acidic, and basic solutes.
abstract: An investigation was made of the correlation between quantitative surface analytical data obtained by XPS and static SIMS and the chromatographic performance of a range of n-alkyl-bonded silica (C1-C18) packing materials. A series of acidic, basic, and neutral solutes was used to study the retention behavior. For comparison, analysis of bulk total percentage carbon (%C) and alkyl surface density of the bonded silica particulates were also included. Significant correlations were observed, in the majority of cases, between the retention factor (k) and the XPS C:Si atomic ratio, which was similar to that obtained between k and the bulk %C or k and the bonded alkyl chain length. Similar significant correlations were also obtained between k and the static SIMS alkyl:Si ion peak area ratios. XPS alkyl:Si atomic ratios were calculated as an estimate of alkyl surface coverage of the silica support, and these correlated well with the surface density calculated from the bulk %C and the surface area of the packing material. The XPS alkyl:Si ratio also demonstrated a significant correlation with the peak asymmetry factor derived for basic solutes. These studies confirm that both XPS and static SIMS can generate surface chemical data from chromatography particulates, which has direct relevance to the prediction of chromatographic behavior. We believe that these techniques will prove to be effective tools to assist in the characterization of chromatographic supports and stationary phases.
authors: Department of Pharmaceutical Sciences, University Park, University of Nottingham, Nottingham NG7 2RD, U.K.
authors: D A
authors: DA
authors: Barrett
authors: V A
authors: VA
authors: Brown
authors: M C
authors: MC
authors: Davies
authors: P N
authors: PN
authors: Shaw