New nucleophilic catalysts for bright and fast peroxyoxalate chemiluminescence

Miniaturized detection applications based on chemiluminescence require fast reaction kinetics for optimum performance. in this work, high-intensity li ght from the analytically useful peroxyoxalate chemiluminescence reaction h as been generated at high rates by employing both single-component and dual -component nucleophilic catalysis. 4-(Dimethylamino)pyridine and its deriva tives were superior to all other bases in terms of reaction speed and inten sity of the generated light and outshone imidazole, which hitherto has been considered as the best catalyst, The light intensity was related to the di fference in pK(a) between the 4-aminopyridine catalyst and the leaving grou p of the reagent, and the optimum Delta pK(a) was found to be close to 0. S imilarly, high light intensities were obtained when mixtures of the imidazo le analogue 1,2,4-triazole and the strong, nonnucleophilic base 1,2,2,6,6-p entamethylpiperidine acted as catalysts, The mechanism behind this was conc luded to be a "base-induced nucleophilic catalysis", where the ancillary st rong base assisted the production of the highly nucleophilic 1,2,4-triazola te anion, which as the actual catalyst then participated in the formation o f 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, whereaf ter the light decayed to darkness within a few seconds, These reaction char acteristics are especially advantageous for sensitive detection application s where the observation volumes and times are limited, e.g., peaks emerging from a capillary-based separation process.