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A novel enzyme-immobilized flow-through interface was designed for sensitive end-column chemiluminescent (CL) detection in open-tubular capillary electrochromatography (OTCEC). Enzyme was covalently bound on an aldehyde-activated polymer membrane immobilized in a flow cell to catalyze the CL reaction that occurred in it. Using glycine as the model analyte, N-(4-aminobutyl)-N-ethylisoluminol-derivatized glycine effused from the OTCEC column and triggered a horseradish peroxidase (HRP)-catalyzed CL reaction, to produce an enhanced detection signal. To obtain a satisfying result for complex biological sample analysis, a thiolated β-cyclodextrin-modified gold nanoparticles-coated OTCEC column was adopted to improve the separation efficiency. Glycine can be assayed in the range of 0.50-200 μM (R(2) = 0.9921) with a detection limit of 0.12 μM (S/N of 3). The whole analysis process can be completed within 13 min with a theoretical plate number of 22,500. Compared to the previously reported solution-phase enzyme catalysis, pre-column and on-column immobilized enzyme catalysis for capillary electrophoresis detection, a significantly reduced enzyme consumption and greatly improved enzyme stability can be achieved with the use of this end-column enzyme-immobilized detection interface. The novel flow cell can be further applied in other capillary electrophoresis modes including capillary zone electrophoresis, capillary gel electrophoresis, and micellar electrokinetic chromatography. It is also suitable for some other detectors such as fluorimetric, ultraviolet-visible absorption spectrometric and electrochemical detectors.

As one of the most sensitive detection mode for CE, chemiluminescence (CL) detection is less developed compared to some other detection modes such as MS and LIF, despite its low equipment cost and simple design. The fact is partly due to the limitation of CL systems suitable for CE. In this paper, a highly sensitive CE-CL strategy was established for the determination of dopamine (DA) and cimbuterol (CM) using acridinium ester as derivatization reagent. Catalyst was not required in this CL detection system. Also, a good sensitivity was obtained due to its quite low background and strong signal. Under the optimal conditions, the presented method has been successfully applied to analyze DA and CM with LODs (S/N = 3) of 2.0 and 0.50 ng/mL, respectively. The linear ranges were 5.0–1500 ng/mL and 2.0–1000 ng/mL for DA and CM, respectively. To validate our method, the levels of DA in human urine samples were detected by this method, and the results showed acceptable accordance with those of ELISA. All the analysis procedure could be completed in 400 s, and the results showed satisfactory sensitivity and selectivity.The approach could also be further extended to rapid analysis of many other compounds including primary and second amines in clinical medicine and biopharmaceutical analysis using acridinium ester as CL derivatization reagent.

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