Performance of a Chromolith RP‐18e column for the screening of β‐blockers

Abstract

The chromatographic performance of a monolithic column (Chromolith RP-18e) was comprehensively examined in the isocratic separation of ten beta-blockers, using ACN-water mobile phases, and compared with the performance of three microparticulate RP columns manufactured with different types of silica: Spherisorb ODS-2, Kromasil C18 and XTerra MS C18. The comparison considered the analysis time, selectivity, peak shape (column efficiency and asymmetry) and resolution, and was extended to a wide range of mobile phase compositions. The Chromolith column showed good performance for the analysis of beta-blockers with regard to the packed columns. In terms of selectivity and analysis time, the greatest similarity was found between the Chromolith and XTerra columns. The addition of a silanol blocking agent (0.1% triethylamine) to both Chromolith and Spherisorb columns yielded, apparently, a similar blocking degree of the silanol groups (based on the similar peak shapes), and gave rise to similar selectivity.

Correction of the deviations in the retention times with Chromolith columns associated to the flow rate: Implications in the modelling of the retention behaviour

“…There is a certain concern about the proper estimation of the dead time 10, 18, which affects the calculation of the retention factor, but the independence from the flow rate is generally accepted. However, the deviations in the retention times with flow rate for the Chromolith column make the corresponding retention factors depend on the flow rate: the plots of k versus the flow rate are sloped, at least for the most retained compounds (Fig.…”

“…Uracil (Acros Organics, Geel, Belgium) was chosen as dead time marker due to its small retention and negligible change in retention time with mobile phase composition 10. Therefore, the hydrophobic interaction of this marker with a C18 stationary phase is rather small.…”

“…This is usually carried out by trial‐and‐error. We reported an interpretive optimisation approach to achieve maximal resolution in minimal analysis time, based on models describing the retention and peak shape as a function of mobile phase composition and flow rate 6. The method was applied to the separation of a group of basic drugs with a Chromolith Performance RP‐18e column, using acetonitrile–water mixtures.…”

Description of the Retention and Peak Profile for Chromolith Columns in Isocratic and Gradient Elution Using Mobile Phase Composition and Flow Rate as Factors

“…Similar plots were obtained with other acetonitrile concentrations in the mobile phase. Theoretically, the retention factor should not depend on the flow (only on the distribution equilibrium), since it is a relative parameter (Equation (1) where F is the flow rate [26,27]. The determination coefficients for the fitted straight-lines were above 0.9999 for the four sulphonamides.…”

Comparison of the performance of non‐ionic and anionic surfactants as mobile phase additives in the RPLC analysis of basic drugs

“…The linearity of the peak half-width plots makes them particularly useful. This has been checked in a variety of examples, including the comparison of chromatographic columns and mobile phases of different nature [30,31]. Equations (2) and (3) allow the prediction of the half-widths (and widths) for peaks eluting at different retention times.…”