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New nucleophilic catalysts for bright and fast peroxyoxalate chemiluminescence
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
2000 (English)In: ANALYTICAL CHEMISTRY, Vol. 72, no 7, 1373-80 p.Article in journal (Refereed) Published
Abstract [en]

Miniaturized detection applications based on chemiluminescence require fast reaction kinetics for optimum performance. in this work, high-intensity light from the analytically useful peroxyoxalate chemiluminescence reaction has been generated at high rates by employing both single-component and dual-component nucleophilic catalysis. 4-(Dimethylamino)pyridine and its derivatives were superior to all other bases in terms of reaction speed and intensity of the generated light and outshone imidazole, which hitherto has been considered as the best catalyst, The light intensity was related to the difference in pK(a) between the 4-aminopyridine catalyst and the leaving group of the reagent, and the optimum Delta pK(a) was found to be close to 0. Similarly, high light intensities were obtained when mixtures of the imidazole analogue 1,2,4-triazole and the strong, nonnucleophilic base 1,2,2,6,6-pentamethylpiperidine acted as catalysts, The mechanism behind this was concluded to be a "base-induced nucleophilic catalysis", where the ancillary strong base assisted the production of the highly nucleophilic 1,2,4-triazolate anion, which as the actual catalyst then participated in the formation of a more reactive transient reagent. All the investigated catalysts reduced the light yield of the reaction due to base-catalyzed breakdown reactions of the reagents and/or intermediates. The intensity peak maximums of these bright and fast reactions typically appeared after less than 10 ms, whereafter the light decayed to darkness within a few seconds, These reaction characteristics are especially advantageous for sensitive detection applications where the observation volumes and times are limited, e.g., peaks emerging from a capillary-based separation process.

Place, publisher, year, edition, pages
2000. Vol. 72, no 7, 1373-80 p.
URN: urn:nbn:se:umu:diva-8534OAI: diva2:148205
Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2012-06-05Bibliographically approved
In thesis
1. Peroxyoxalate Chemiluminescence for Miniaturized Analytical Flow Systems
Open this publication in new window or tab >>Peroxyoxalate Chemiluminescence for Miniaturized Analytical Flow Systems
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the peroxyoxalate chemiluminescence (POCL) reaction and its application as a detection technique in flow systems for chemical analysis. Particularly, miniaturized flow systems aimed for separation of molecules. In such systems, a high light intensity and a rapid development of the emission are the desired reaction characteristics, for reasons discussed in this text. The work tries to develop an understanding of the chemical processes involved in POCL, with special emphasis to the species favoring or hindering a rapid light evolution. Hence, is the focus placed on the nature of catalysis and the desired properties of substances acting as catalysts in this reaction. Consequently, the scientific papers on which this work is founded includes both systematic stopped-flow studies of catalyst candidates and of the causes for diminished light emission. In addition, multivariate strategies for reaction optimization in practical analysis situations are treated, and the application of the POCL technique to detection of serum-extracted neuroactive steroids, derivatized with fluorescent moieties, is presented.

From the experiments in this thesis it is clear nucleophilic catalysts are the most efficient enhancing compounds, which means that they must possess a carefully balanced characteristics of nucleophilicity, leaving group ability, and basicity. The investigations also conclude that the feature of basicity efficiently can be delegated to a non-nucleophilic co-catalyst, which allow the use of nucleophilic catalysts that need to be deprotonated to be active. This thesis also shows the importance of minimizing the amount of competing nucleophiles at the site of reaction to maintain the emission. This implies that also solvents and buffer substances should be carefully chosen not to interfere with the emission process.

The most promising combination of catalysts found in this work was 4,5- dichloroimidazole together with 1,2,2,6,6-pentamethylpiperidne. This arrangement was capable of speeding the reaction more than tenfold while increasing the maximum emission intensity by about the same factor.

37 p.
peroxyoxalate, chemiluminescence, nucleophilic catalysis, non-nucleophilic base, imidazole, triazole, aminopyridine, miniaturized, flow system, capillary electrophoresis, multivariate
Research subject
Analytical Chemistry
urn:nbn:se:umu:diva-16 (URN)91-7305-377-5 (ISBN)
Public defence
2003-01-24, 00:00
Available from: 2003-01-24 Created: 2003-01-24 Last updated: 2012-06-05Bibliographically approved

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