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With so many HPLC columns on the market we present a simple guide to what's important when making your stationary phase and column dimension choices.
An excerpt from LCGC's e-learning tutorial on column selection for RP-HPLC at CHROMacademy.com
There are many factors that influence the performance of a high performance liquid chromatography (HPLC) stationary phase, of which the chemical nature of the bonded phase ligand is important, but by no means all encompassing. Minor manufacturing parameters such as the method of electropolishing the internal surface of the column can also have an effect on the selectivity and efficiency produced by a particular column.
Few of us have time to study each individual parameter (of which there are hundreds) and assess their interactive effects on the selectivity of our stationary phases. We need readily accessible measures of column performance to identify similar or orthogonal chemistries to those we are currently using, or to gain an insight into which column types might work for particular applications.
Several attempts have been made to produce a "definitive" set of chemical probes to best characterize the huge number of stationary phases available (well over 1000 different types are currently available). As yet a harmonized set of test probes and methodologies has not been identified, however three, independent, publicly available databases of HPLC columns exist today:
Figure 1: Schematic representations of the five interactions described by the hydrophobic subtraction model (adapted from reference 5).
The PQRI database is the best populated, with 588 columns, and is a very useful tool to aid HPLC column selection. A description of the Tanaka test probes is given below to help understand the various classifications, with the analogous PQRI test probes indicated in parentheses. It should be noted that the PQRI classification uses different chemical probes to the Tanaka (now ACD) database but the results describe a similar chemical behaviour.
Most of these groups have used chemometric approaches to produce quantitative comparisons between column characteristics based on principal component analysis (PCA) or tools to visualize the relative groupings of commercially available columns according to their key descriptors.
References available in the on-line edition: www.chromatographyonline.com/Essentials0313