Reagent selection chemiluminescence detection, reagents

Chemiluminescence detection in capillary electrophoresis (CE) has attracted much attention as a promising way to offer excellent analytical selectivity and sensitivity. Several reagents, such as luminol, acridinium, peroxyoxalate, and tris(2,29-bipyridine)ruthenium(II) complex have been utilized. Since chemiluminescence detection is approximately 102—106 times more sensitive than spectrophotometric and fluorometric detections, its combination with isoelectric focusing may result in a highly sensitive analytical tool for amphoteric compounds, e.g., proteins and peptides. A detector using luminol-H202 chemiluminescence has been characterized in a very simple and inexpensive setup, but only pressure-driven mobilization of the zones was effective. [68],... 

Both flow-based and array-based chemiluminescence detection systems have been incorporated into micro total analysis systems (pTAS) and other microfluidic devices in conjunction with the myriad recent advances and innovations in microfluidics technology such as device fabrication, sample and reagent preparation and handling, and analyte selectivity, as described throughout this Encyclopedia. 

Selectivity of chemiluminescence reactions can be a concern. Some reactions are essentially compound-specific. An example is tetrakis(dime-thylamino)ethylene, which undergoes chemiluminescence reaction only with Oz- Although such specificity provides freedom from measurement interference, that chemiluminescence reaction then lacks universal application. In other cases, several species could yield emission with a given reagent. These situations then require coupling of the chemiluminescence detection with some sort of highly selective physical or chemical step (such as chromatography, immunoassay, enzyme reactions) to achieve an interference-free measurement. An... 

Numerous applications involve coupling liquid-phase chemiluminescence detection to physical or chemical separation processes. Conversely, adequate selectivity can also be achieved for particular analytes in a range of sample matrices through a judicious selection of reagent and reaction conditions. Successful detection strategies have been employed for HPLC, flow analysis, electrophoresis, immunoassay labels, DNA probes, and enzyme reactions. 

Chlorine dioxide is a highly selective chemiluminescence reagent for two sulfur compounds hydrogen sulfide and mercaptoethanol. The exact reaction pathway is unknown, although it is thought that sulfur atoms produced in the reaction recombine to form excited Si molecules, as in the FPD. A detection limit of 3 pg 1 hydrogen sulfide has been quoted. 

MSC system for oxalate determination with chemiluminescence detection. HC holding coil R reagent RC reaction coil SV selection valve V solenoid valve. 

The use of chemiluminescence reactions for the detection of metal ions by liquid chromatography was recently reported [59,60]. The detectors made use of the chemiluminescence produced in the reaction between luminol and hydrogen peroxide which is catalyzed by transition metals. The column effluent was mixed with the reagents in order to yield the chemiluminescence. The reaction was fast and was carried out at room temperature. By varying the pH of the buffer, selectivity towards certain metals was also achieved. For example, at pH 10-11 nickel could be analyzed but lead and aluminium were inactive at pH 13-14, the converse was true [59]. Aminco-Bowman has marketed a liquid chromatographic system in which amino acids and amines are analyzed by means of the fluorescence produced on reaction with the reagent fluorescamine. Fluorescamine does not fluoresce, but it does react with primary amino groups to produce fluorescent derivatives. The reaction is instantaneous and may be carried out at room temperature, usually at pH 9. This detection system promises to be far more sensitive than the ninhydrin detection system and is much more easily adapted to HPLC. 

Chemiluminescence is a very sensitive and selective technique. Reagent types, analytes, and detection limits have been summarized in a review by Imai.56 Chemiluminescence has been applied to the analysis of compounds that exhibit low UV absorbance, including metal ions, amino acids, fatty acids, and bile acids. Other detectors include detectors for radioactivity, nuclear magnetic resonance (NMR), and surface-enhanced Raman spectroscopy. Radioactivity detection is one of the most selective detectors, as only components that have been radiolabeled will be detected. The interface of NMR with HPLC and has been discussed in detail by Grenier-Loustalot et al.57 Surface-enhanced Raman spectroscopy is another technique that... 

Flow analysis has been used to investigate the fundamental chemistry of chemiluminescence and bioluminescence reactions, to optimise post-column chemiluminescence reaction conditions for liquid chromatographic detection and to quantify analytes in relatively simple or synthetic matrices [68]. In recent years, there has been a pronounced increase in the application of these methods to the analysis of real sample matrices [69]. This has usually been achieved by a combination of efficient in-line sample treatment, e.g., use of solid-phase reagents for concentrating selected analytes and/or for removing the sample matrix and exploitation of more inherently selective reactions [70,71],... 

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