Abstract: The characteristics of bias caused by split-flow electrokinetic injection (SEKI), a new sample injection method applied in coupled flow injection-capillary electrophoretic system(FI-CE), was investigated using pseudoephedrine hydrochloride, a basic drug and ibuprofen, an acidic drug, as model analytes. It was found that bias imposed by SEKI under the conditions of continuous sample matrix/running buffer was similar to that did by electrokinetic injection (EKI). The linearity of calibration curve provided by SEKI was similar to that offered by non-bias hydrodynamic injection (HDI) but significantly better than that obtained by EKI. These features were exploited to improve analytical performances in simultaneous determination of the minor ingredient of pseudoephedrine hydrochloride and the major ingredient of ibuprofen in pharmaceutical preparation. Detectability of 0.7 mg/L for pseudoephedrine hydrochloride, was achieved at a sample throughput rate of 24 times per hour which is 30% lower than that obtained by HDI-based conventional CE. Eleven runs of a test solution containing 13.1 mg/L pseudoephedrine hydrochloride and 81.4 mg/L ibuprofen produced relative standard deviations (RSDs) of 2.8% for the minor ingredient and 1.2% for the major ingredient, which were improved in comparision to that obtained by HDI-based conventional CE. Analytical results for two batches of compound ibuprofen tablets by the SEKI-based FI-CE approach were in good agreement with that obtained by a conventional high performance liquid chromatographic method.

Key words: hydrodynamic injection, compound ibuprofen tablet , electrokinetic injection, flow injection, ibuprofen, pseudoephedrine hydrochloride, split-flow electrokinetic injection, capillary electrophoresis