Effect of pH of Eluent on Elution Volume and Plate Number (ODP)
By using an alkaline eluent with a higher pH than the pKa sample value, basic
drugs with tertiary amino groups will be retained by the column because the amino
groups are not dissociated. As shown here, at pH11, the elution volumes of most
drugs show the highest values and the separation of the drugs is the best at pH11.
Also theoretical plate numbers of most drug components show the highest values
at pH11. For the analysis of basic drugs using Asahipak ODP
columns, sharp peaks can be obtained by using an alkaline eluent.
In addition, the separation of both drug components and their impurities becomes easier because the components are retained more strongly
by using an alkaline eluent.
Column : Shodex Asahipak ODP-50 4D (4.6mmID*150mm)
Eluent : 25mM Phosphate buffer/CH3CN=60/40
Flow rate : 0.6mL/min
Detector : UV(254nm)
Column temp. : 30°C