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Peroxyoxalate Chemiluminescence for Miniaturized Analytical Flow Systems
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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.

Place, publisher, year, edition, pages
2003. , 37 p.
Keyword [en]
peroxyoxalate, chemiluminescence, nucleophilic catalysis, non-nucleophilic base, imidazole, triazole, aminopyridine, miniaturized, flow system, capillary electrophoresis, multivariate
Research subject
Analytical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-16ISBN: 91-7305-377-5 (print)OAI: oai:DiVA.org:umu-16DiVA: diva2:141505
Public defence
2003-01-24, 00:00
Available from: 2003-01-24 Created: 2003-01-24 Last updated: 2012-06-05Bibliographically approved
List of papers
1. Determination of C-21 ketosteroids in serum using trifluoromethanesulfonic acid catalyzed precolumn dansylation and 1,1’-oxalyldiimidazole postcolumn peroxyoxalate chemiluminescence detection
Open this publication in new window or tab >>Determination of C-21 ketosteroids in serum using trifluoromethanesulfonic acid catalyzed precolumn dansylation and 1,1’-oxalyldiimidazole postcolumn peroxyoxalate chemiluminescence detection
1998 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 70, no 23, 5002-5009 p.Article in journal (Refereed) Published
Abstract [en]

A new procedure for the quantitation of C-21 ketosteroids using trifluoromethanesulfonic acid-catalyzed precolumn dansylation and coupled column liquid chromatographic separation, followed by postcolumn 1,1‘-oxalyldiimidazole peroxyoxalate chemiluminescence detection is presented. In the simultaneous optimization of chromatographic resolution and chemiluminescence intensity, a coupled column chromatographic system and a stopped-flow system were used. An eluent containing 20 mM phosphate buffer at pH 6.7 accomplished an efficient separation of 3α-hydroxy-5β-pregnan-20-one from a mixture containing 10 C-21 ketosteroids. Phosphate buffer also proved to be the most advantageous, among the six buffers tested, for sensitive detection. Experimental design and multivariate data analysis were used to characterize and optimize the postcolumn reaction chemistry in the chromatographic system. A valid full factorial design with excellent predictability showed that the flow rates for both 1,1‘-oxalyldiimidazole and hydrogen peroxide were the factors most strongly affecting the sensitivity of the system. The theoretical plate numbers were above 11 000 for all 10 dansylated ketosteroids. The 3σ detection limit estimated from 3α-hydroxy-5β-pregnan-20-one calibration curve data was 1.6 pmol (n = 4, 125 μL injected) and spiked serum containing 0−74 pmol of this compound showed overall recoveries of 73 ± 9% (n = 12). Quantitation of 3α-hydroxy-5β-pregnan-20-one was finally carried out on 45 serum samples and the results compared to those from a radioimmunoassay (RIA) method. The data acquired with the procedure described in this work compare well with the results from RIA, which confirms the reliability of the new analytical procedure.

Place, publisher, year, edition, pages
Washington: American Chemical Society (ACS), 1998
Keyword
performance liquid chromatography, bile-acids, steroids, reagent, system
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-3055 (URN)10.1021/ac980511s (DOI)000077278700031 ()
External cooperation:
Available from: 2003-01-24 Created: 2003-01-24 Last updated: 2017-12-14Bibliographically approved
2. Heterocyclic compounds as catalysts in the peroxyoxalate chemiluminescence reaction of bis(2,4,6-trichlorophenyl)oxalate
Open this publication in new window or tab >>Heterocyclic compounds as catalysts in the peroxyoxalate chemiluminescence reaction of bis(2,4,6-trichlorophenyl)oxalate
1998 (English)In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 361, no 3, 205-215 p.Article in journal (Refereed) Published
Abstract [en]

Substituted imidazoles and leaving groups known from other areas of chemistry have been tested for catalytic efficiency in the peroxyoxalate chemiluminescence (PO-CL) reaction, using bis(2,4,6-trichlorophenyl)oxalate (TCPO) as reagent. Catalytic activity was found for 1,2,4-triazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole and 4,5-dichloroimidazole, while 2-mercaptoimidazole, 2-nitroimidazole, 4-nitroimidazole, benzimidazole, benzotriazole, thiazole, o-benzoic sulfimide, phthalimide, succinimide, 2(1H)-pyridone and 1,2,3-benzotriazine-4(3H)-one yielded no detectable chemiluminescence under the conditions used. None of the tested compounds was more efficient than imidazole in catalyzing the PO-CL reaction. Spectrophotometric measurements of the catalytic breakdown of TCPO showed that an intermediate was formed with almost all catalysts, and that intermediates that were more stable or present at lower concentration led to a reduced catalytic efficiency in the PO-CL reaction of TCPO.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 1998
Keyword
chemi-luminiscence detection, performance liquid chromatography, flow injection analysis, hydrogen peroxide, fluorescent compounds, detection system, aryl oxalates, 1, 1'-oxalyldiimidazole, mechanism, imidazole
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-3056 (URN)10.1016/S0003-2670(98)00029-4 (DOI)000073224600003 ()
External cooperation:
Available from: 2003-01-24 Created: 2003-01-24 Last updated: 2017-12-14Bibliographically approved
3. Very fast peroxyoxalate chemiluminescence
Open this publication in new window or tab >>Very fast peroxyoxalate chemiluminescence
1999 (English)In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 400, no 1-3, 257-264 p.Article in journal (Refereed) Published
Abstract [en]

Peroxyoxalate chemiluminescence (PO-CL) detection offers an advantage in chromatographic detection, by the virtue of its multiple unique selectivities and high sensitivity. However, many of the analytical separation techniques available today require observation times in the millisecond range to preserve the band resolution, and as the reaction kinetics of the PO-CL reaction is considerably slower, extra flow elements are needed to observe the reaction in a time window at maximum emission intensity. Since these flow elements increase the complexity of the system and contribute to band-broadening, the rational way to adapt PO-CL detection to miniaturised separation systems is to speed up the reaction, so that it emits an initial burst of light within the acceptable detection time-frame. Although this may result in a lower overall quantum yield, the actual detection sensitivity could be equal to, or better than slower PO-CL systems. By making careful selections of oxalic reagent and catalyst(s) the reaction can be fine-tuned to maximise the intensity. In this work, the time-dependent light emission from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) was studied under the catalytic influence of imidazole, 1,2,4-triazole, 4-dimethylaminopyridine (DMAP), and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) in acetonitrile. Both DMAP and DBU accelerated the reaction substantially, but the best combination of reaction speed and intensity was found for a mixture of 0.5 mM DBU and 5 mM 1,2,4-triazole, which reached its maximum emission after only 40 ms and had an emission intensity comparable to that seen with 5 mM imidazole as catalyst.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 1999
Keyword
chemiluminescence, peroxyoxalate, fast reaction, 1, 2, 4-triazole, 1, 8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-3057 (URN)10.1016/S0003-2670(99)00626-1 (DOI)000084204200021 ()
External cooperation:
Available from: 2003-01-24 Created: 2003-01-24 Last updated: 2017-12-14Bibliographically approved
4. New nucleophilic catalysts for bright and fast peroxyoxalate chemiluminescence
Open this publication in new window or tab >>New nucleophilic catalysts for bright and fast peroxyoxalate chemiluminescence
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.

Identifiers
urn:nbn:se:umu:diva-8534 (URN)
Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2012-06-05Bibliographically approved
5. Preliminary Kinetic Evaluation of Co-Catalyzed Acidic Azoles for Peroxyoxalate Chemiluminescence Detection in Miniaturized Flow Systems
Open this publication in new window or tab >>Preliminary Kinetic Evaluation of Co-Catalyzed Acidic Azoles for Peroxyoxalate Chemiluminescence Detection in Miniaturized Flow Systems
Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-3059 (URN)
Available from: 2003-01-24 Created: 2003-01-24 Last updated: 2010-01-13Bibliographically approved

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