IMPROVEMENTS IN LIQUID-CHROMATOGRAPHY COLUMN LIFE AND METHOD FLEXIBILITY BY SATURATING THE MOBILE PHASE WITH SILICA

We describe a technique which may expand the opportunities for liquid chromatography (LC) methods development. It has not been feasible to use high pH water-based mobile phases with silica packings, even those coated with octadecylsilane. A principal failure mode of such packings with both high pH and high temperature mobile phase is the dissolution of silica. We show that this can be controlled by equilibrating the mobile phase with silica using an appropriate column mouted in the oven ahead of the analytical column. We describe some early results of this technique for determining tricyclic antidepressant drugs at a mobile phase pH of 10.7 on uncoated 5-μm silica particles. Using an inorganic instead of an organic base also permits UV detection closer to 200 nm where most organic bases have become opaque. We measured the silicon dissolved in the column effluent by atomic absorption (AA). We used an injection procedure which permits the AA burner to take up solution at its optimum rate while the LC is used at any lower mobile phase flow-rate. © 1979.