Use of Drylab to compare octadecylsilane and carbon supports for reversed-phase chromatography of triazine herbicide test solutes

One of the most important aspects of method development in reversed-phase high-performance liquid chromatography (RPLC) is the accurate prediction of the resolution as one or more experimental variables (usually the mobile-phase composition) are changed. By use of commercially available computer simulation programs, e.g. Drylab 2000, data from a few initial experimental runs are used to predict how the separation will vary with composition so that a computer program can then rapidly locate the optimum conditions. Assumption of a linear relationship between log k′ (retention factor) and φ (volume fraction of organic modifier in the element) minimizes the number of initial runs required for a separation and is usually adequate when the range of φ is not large. In this work the linearity of plots of log k′ against φ for octadecylsilane-coated silica (ODS) and carbon-coated zirconia (C-ZrO₂) columns were compared and the plots were used to determine whether prediction of the separation of triazine herbicides was adequate. Analysis of the slopes and intercepts of such plots are presented for both types of columns.