HPLC of basic drugs using non-aqueous ionic eluents: evaluation of a 3 mum strong cation-exchange material

HPLC columns packed with 3 microm particle size HPLC Technology Techsphere SCX (propylsulfonic acid-modified) silica offer considerable advantages over 5 microm SCX packings in the analysis of basic drugs using 100% methanol eluents containing an ionic modifier such as ammonium perchlorate. The basic drugs studied included clozapine and norclozapine, olanzapine, quinine and quinidine, and amitriptyline, nortriptyline, imipramine and desipramine. The 3 microm column was not only more efficient for a given column length compared with 5 microm materials, but also elution times were less, a phenomenon observed in reversed-phase systems. The high efficiencies and excellent peak shapes obtained with the 3 microm SCX-modified packing together with the relatively low back-pressures attained show that such materials deserve serious consideration by laboratories involved in the analysis of basic drugs. Manufacturers should offer such packings as a matter of routine. Alternative ionic modifiers such as ammonium acetate are available for use with mass spectrometric detection if required.