In gradient elution separations, it may be required to change either column length (to increase resolution or shorten run time) or column diameter (for an increase in sensitivity or for preparative separations). In either of these changes of column dimensions, it is usually desired to maintain the same relative band spacing (selectivity), so as to increase resolution in proportion to (column plate number)1/2 when increasing column length, or to maintain constant resolution when changing column diameter. Changes in band spacing as a result of change in column size are of special concern when developing procedures for preparative chromatography under gradient conditions.

A method is proposed for the sensitive chiral analysis of amino acid enantiomers by high-performance liquid chromatography (HPLC) using computer modeling with DryLab. Thus the enantiomers of a mixture of seven racemic amino acids were resolved as their DNP derivatives from each other and from the peak of the hydrolyzed reagent, employing a quinine carbamate-based chiral anion exchange-type chiral stationary phase (CSP) and aqueous buffered mobile phases. Average errors of prediction of retention times lay between 2 and 8%. Finally, a highly improved HPLC gradient method resulted in almost all components being baseline separated and equally spaced and accelerated by a factor of more than 3 compared to the initial run.