Comparison of the elution profiles of a weakly basic drug on cyanopropyl-bonded silica cartridges from different manufacturers and different batches

Abstract

A comparison is made of the recoveries obtained for the solid-phase extraction (SPE) of an aqueous 1 μg ml -1 solution of papaverine on nine different batches of cyanopropyl-bonded silica (CN) phases from three different suppliers. The elution profile with up to 3 ml of methanol or methanol containing 0.1% propylamine was set up, whereby intra- and inter-day variations were taken into account. For each volume level and both eluents, significant differences could be demonstrated between the mean recoveries obtained on different batches of CN sorbents. If the volume of methanol used for the elution is increased, or if the eluotropic strength is increased by addition of propylamine, then the differences in mean recoveries are smaller. The nine sorbents could be divided into three groups according to the relative importance of the apolar dispersion forces and the ionic interactions for the adsorption of papaverine. In addition to between-batch and between-manufacturer variations, the SPE method with 1 ml of 0.1% propylamine in methanol as eluent yielded differences in recovery of ±10% from day to day.