Supported liquid membrane technique for selective sample workup of basic drugs in plasma prior to capillary zone electrophoresis.

The potential of using the supported liquid membrane (SLM) technique for pretreatment of plasma samples before analysis with capillary zone electrophoresis (CZE) has been investigated. A basic drug, bambuterol, was used as a model substance in a system, where either 6-undecanone or a mixture of di-n-hexyl ether (DHE) and tri-n-octyl phosphine oxide (TOPO) was used as membrane liquids. It was found that the electropherograms obtained after SLM enrichment of bambuterol in plasma samples were as clean as when aqueous samples containing the same substance were processed in the same way. The low ionic strength of the SLM treated blood plasma samples permitted subsequent sample stacking in the CZE step. The linearity of the detector signal for different concentrations of bambuterol in plasma was satisfactory from 50 to 1000 nmol/L with regression co-efficients of 0.997 using 6-undecanone as membrane liquid and 0.999 with the other liquid. In both systems, the confidence interval of the intercept included the origin. The detection limit was about 50 nmol/L. The long-term stability of the two membrane liquids proved adequate as a membrane lasted at least through the working day.