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A capillary electrophoresis (CE) with chemiluminescence (CL) detection method was developed for the simultaneous quantification of 5-hydroxyindoleacetic acid (5-HIAA) and 5-hydroxytryptamine (5-HT). In this method, CdTe quantum dot (QD) and horseradish peroxidase (HRP) were used as enhancing reagents to co-catalyze the post-column CL reaction between luminol and hydrogen peroxide, achieving highly efficient CL emission. 5-HIAA and 5-HT inhibit the CL emission resulting to the formation of negative peaks in electropherogram. The degree of CL suppression is proportional to the concentration of 5-HT and 5-HIAA. The linear ranges for the determination of 5-HIAA and 5-HT were 2.5 × 10 −8 –2.5 × 10 −6 M and 2.5 × 10 −8 –5.0 × 10 −6 M with detection limits (signal/noise = 3) of 7.0 × 10 −9 M and 6.0 × 10 −9 M, respectively. Intraday precision do not exceed 5.0%. The accuracy was confirmed by the recoveries ranged from 98% to 104%. The present method was successfully applied for the quantification of 5-HIAA and 5-HT in human urine. The concentrations of 5-HT and 5-HIAA in human urine were found to be in the range of 0.78–1.2 μM and 3.2–5.1 μM, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A sensitive method based on quantum dot (QD)-enhanced capillary electrophoresis–chemiluminescence (CE–CL) detection was developed for simultaneous determination of dopamine (DA) and epinephrine (E). In this work, CdTe QD was added into the running buffer of CE to catalyze the post-column CL reaction between luminol and hydrogen peroxide, achieving higher CL emission. Negative peaks were produced due to the inhibitory effects on CL emission from DA and E eluted from the electrophoretic capillary. The decrease in CL intensity was proportional to the concentration of DA and E in the range of 8.0×10−8–5.0×10−6 M and 4.0×10−8–5.0×10−6 M, respectively. Detection limits for DA and E were 2.3×10−8 M and 9.3×10−9 M, respectively. Using this method, the levels of DA and E in human urine from healthy donors were determined. [Copyright &y& Elsevier]

Abstract: A microchip electrophoresis (MCE) method with chemiluminescence (CL) detection was developed for the determination of carnosine-related peptides, including carnosine, homocarnosine, and anserine, in biological samples. A simple integrated MCE–CL system was built to perform the assays. The highly sensitive CL detection was achieved by means of the CL reaction between hydrogen peroxide and N-(4-aminobutyl)-N-ethylisoluminol-tagged peptides in the presence of adenine as a CL enhancer and Co2+ as a catalyst. Experimental conditions for analyte labeling, MCE separation, and CL detection were studied. MCE separation of the above-mentioned three peptides took less than 120s. Detection limits (signal/noise ratio [S/N]=3) of 3.0×10−8, 2.8×10−8, and 3.4×10−8 M were obtained for carnosine, anserine, and homocarnosine, respectively. The current MCE–CL method was applied for the determination of carnosine, anserine, and homocarnosine in human cerebrospinal fluid (CSF) and canine plasma. Homocarnosine was detected at the micromolar (μM) level in the CSF samples analyzed, whereas the levels of carnosine and anserine in these samples were below the detection limit of the assay. Interestingly, both carnosine and anserine were detected in the canine plasma samples, whereas homocarnosine was not. [Copyright &y& Elsevier]