Abstract: A flow-through conical reservoir was used to couple a flow injection (FI) system to a CZE system. The reservoir was attached to the outlet of the FI system. One end of the capillary column was positioned in the conical reservoir together with a grounded electrode. Samples were injected into the FI system and transported to the reservoir. Here, a portion of the sample plug was electrokinetically injected into the capillary. The same electrolyte was used as the carrier stream for the FI system and the running buffer. The system was demonstrated using benzoic acid and benzoic acid/magnolol mixtures as model analytes and 25 mM sodium tetraborate at pH 9.3 as the carrier/running buffer. Sample volumes of 40 µL were injected into the carrier stream (0.7 ml/min). The electrophoretic separations were performed on an uncoated capillary of 35 cm x 75 µm i.d. with an applied voltage of 12 kV (also injection voltage) and on-column UV detection at 224 or 254 nm. The precision of the coupled system was evaluated by repeated measurement of the peak heights and retention times for 200 mg/l benzoic acid. The RSD (n = 7) were 2.1% for peak heights and 0.4% for retention times. Similar measurements for a mixture of 150 mg/l benzoic acid and 140 mg/l magnolol yielded RSD (n = 7) of 2.3% for peak heights. The sampling frequency was 18/h.

Abstract: A FI-HPCE method was developed for traditional Chinese medicines. A new flow injection sample introduction interface was proposed for capillary electrophoresis. Using the FI-HPCE system, buffer concentration, pH, voltage and percentage of methanol were optimized to sep. magnolol and honokiol from other constituents in Cortex Magnolial Officinalis and their medicinal preparations The sample throughput was 10/h, the relative standard deviation at 138 µg/mL magnolol was 2.1% (n=6) and the recoveries were in the range of 96%~102.9%.