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The most important tool in HPLC method development is stationary phase selectivity. The number of commercially available RP phases shows the importance of the stationary phase. These are approximately 750 different stationary phases today, and every year new packing materials are introduced. The user now has the task to select the right column for his application from this large number of HPLC phases. This can be very difficult. Very often it involves a costly and time consuming optimization of the mobile phase.
The optimization of a seperation becomes much easier once the optimal stationary phase has been found. The Phase Optimized Liquid Chromatography (POPLC®) uses a completely new approach in method development and optimization.
After a rough first choice of mobile phase, only the stationary phase needs to be optimized.
POPLC® is based on the theory of the "PRISMA Model" that has been used before to optimize mobile phases in Liquid Chromatography [Szabolcs Nyiredy, K. Dallenbach-Tölke, O. Sticher in JPC (Journal of Planar Chromatography) 1, (1988), Seite 1241]. (Fig. 4)
The vertical sides of the prism correspond to the retention strength of a given analyte. The optimal retentin strength for this analyte lies on a surface that is built by the upper irregular triangle of the prism. It can be realized by combination of the stationary phases A, B and C. Technically this is realized by using a segmented column system.
First retention times are determined with isocratic chromatographic runs of the analytes on different stationary phases using the same mobile phase which is chosen by experience or trial. The stationary phases used for these basic measurements should be of strongly different selectivity. For example C18, C18 with enhanced polar selectivity and Phenyl, C30 or Cyanopropyl (CN) could be used for this purpose. The retention of the analytes on any of these phases is different, due to different mechanisms of interaction. The individual retention times are then used for calculations that are performed by optimization software. The software calculates the combination of column segments.