“Can you advise me on how to select a column for a particular molecule?
e.g. Molecule is acidic in nature; Molecule is basic in nature; Molecule is neutral in nature; In which cases would we prefer cyano and amino columns; When we should use an amino column for the analysis of sugars on a Refractive Index detector; Why a lot of noise is produced which is not produced while using a union; What is the best solvent for preservation of amino columns, excepting hexane?"
“The process of selecting a column for a particular analysis is quite complex and requires a good knowledge of HPLC method development. I recommend the book ‘Practical HPLC Method Development’ by Lloyd Snyder, Joseph Kirkland and Joseph Glajch or, if you can, attend a good training course on HPLC method development such as those offered by MTS. As a general rule the type of column that you select will depend on the type of HPLC that you are using and the selection of the type of HPLC is based on the polarity and molecular weight of the molecule you wish to analyse. Types of HPLC include: partition, adsorption, size exclusion chromatography (SEC) and ion exchange chromatography (IC). Of these partition in the reversed phase (polar mobile phase) is the most commonly used. Acidic, basic and neutral molecules may be analysed using all these types of HPLC and so many columns can be used. Sorry that my answer cannot be more precise but the fact is that it is not just the acidic or basic nature of the molecule but also its other features that dictates the choice of column. My first choice with a new molecule is reversed phase partition HPLC if possible, using a C18 column and only move to other phases if necessary.