Extended life for blood serum analysis columns using dual zone chromatographic materials

Column lifetimes of novel dual zone material (DZM) adsorbents were evaluated by direct serum injection analysis for drugs by high-performance liquid chromatography. Porous silica was converted to DZMs in which the outer zone was enriched in an immobilized lipophobic moiety, the perfluorobutylethylenesilyl group, and the internal zone was enriched in a lipophilic octadecylsilyl group. Performance during repetitive serum analyses for phenobarbital and carbamezepine by reverse phase HPLC was compared to that of control adsorbents of the same composition but without the dual zone distribution. The DZM columns had lifetimes up to 4 times longer than the controls. Furthermore, under these conditions, even the control columns had considerably longer lifetimes than conventional but more retentive reverse phase columns. The DZM column lifetimes also appeared to be comparable to or better than those of the recently introduced Pinkerton packings and have much better adsorbent design flexibility and pH operating latitute.