Procedure for the Choice of an RP-Column

With regard to the choice of a column, several factors play a role, of course, such as price, stability in routine work, charge-to-charge reproducibility, availability in the event of transfer of the method, possible different column sizes, if necessary unproblematic scale-up, reliability of suppliers, etc. Here, we should consider first of all the principal question of selectivity. 

Of coruse, a imiversal column does not exist, and will probably never be realized. However, one may speculate about which properties that a fictitious, ideal RP-column with imiversal selectivity would need to have. 

Very simplistically, one would need any type of modem LiChrospher or Zorbax ODS based on an alkali-resistant silica gel in two versions, 50 and 300 A. 

As noted above, the following three factors are relevant for selectivity hydro-phobicity, silanophilicity, and steric aspects. A phase possessing these three properties would have the necessary pre-conditions for a separation of nearly all types of analytes in RP-HPLC. 

The interactions would be individually adjusted for each class of compound by the eluent, e.g. +5% tetrahydrofuran, n-butanol, isopropanol, etc., for neutral components, +/-0.5 pH units for ionic components. The final step of optimization imder special consideration of the run time would involve a change of the gradient (starting and end percentages of B, steepness, gradient volume) and the temperature. 

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