| In recent years, capillary electrophoresis (CE) has shown a tremendous growth in manyfields because of its excellent separation efficiency, short analysis time, minimal need ofsamples and high versatility in terms of separation modes. The most commonly used detectionmethod in CE is UV spectrometry. However, the poor concentration sensitivity, restricting itsapplication in the analysis of biological samples containing the analytes in low concentrations.The integration of solid phase extraction (SPE) with CE can overcome the aforementionedlimitation effectively.In this paper, an on-line coupling system of SPE with CE (SPE-CE-UV) is presented,which uses a home-designed sheath flow gating interface (SFGI). This system allows forautomatic and precise transfer an exact fraction of eluent from SPE to CE under the control ofa programmed computer, implying that it is convenient for the present SPE-CE-UV systemto perform the “zone-cutting†operation.After the operating conditions for SPE, CE and SFGI were optimized independently, theSPE-CE-UV system was evaluated using a poly methacrylic acid-ethylene dimethacrylate(MAA-EDMA) silica-microspheres-encapsulated monolithic column (1.5cm long，250μmi.d.) as SPE column，and clenbuterol (CLB) as the test analyte. A complete run composing ofsample loading, elution, accumulation-injection，washout and separation steps can be finishedin20min. The enrichment factors of the independent SPE and the system are575and563,respectively. The plate numbers are15376and23033for the independent CE and thecoupling system, respectively. The above experimental results indicate that the system doesnot degrade the SPE enrichment factor and CE separation efficiency. The detection limit forCLB is2.8μg/L (S/N=3).Finally, the present SPE-CE-UV system was applied to the determination of CLB inurine. The recoveries of the samples spiked at three levels are in the range of92.64-106.32%，and the precision is4.6%(RSD%, n=7), demonstrating that the system is reliable in the realsample analysis. |
