Peroxyoxalate chemiluminescent assay for oxidase activities based on detecting enzymatically formed hydrogen peroxide

Determination of aromatic compounds by high-performance liquid chromatography with on-line photoreactor and peroxyoxalate chemiluminescence detection

This paper describes a novel high-performance liquid chromatographic (HPLC) method for the determination of aromatic compounds with peroxyoxalate chemiluminescence (PO-CL ) detection following on-line UV irradiation. Aromatic compounds were UV irradiated (254 nm, 15 W) to generate hydrogen peroxide, which was determined via PO-CL detection using a mixture of bis(2,4,6-trichlorophenyl)oxalate (aryloxalate) and 2,4,6,8-tetrathiomorpholinopyrimido[5,4-d]pyrimidine (fluorophore) as a post-column CL reagent. Generation of hydrogen peroxide from aromatic compounds was confirmed using a flow injection analysis (FIA) system incorporating an enzyme column reactor immobilized with catalase. The conditions for UV irradiation were optimized using benzene and monosubstituted benzenes (phenol, benzaldehyde, nitrobenzene and N,N-dimethylaniline) by an HPLC system to evaluate the analytical performance of the proposed system. The detection limits for benzene and monosubstituted benzenes were in the range 2.1-124 pmol/injection at signal:noise (S:N) ratio = 3. Monocyclic and polycyclic hydrocarbons were also employed to investigate their CL properties. The possibility of PO-CL detection for a wide variety of aromatic compounds was shown for the first time.

Reactivation of horseradish peroxidase with imidazole for continuous determination of hydrogen peroxide using a microflow injection-chemiluminescence detection system

A method for reactivation of inactivated horseradish peroxidase (HRP) was studied and exploited in an assay for hydrogen peroxide (H(2)O(2)). Addition of imidazole into a mobile phase made continuous determination of hydrogen peroxide (H(2)O(2)) possible by micro fl ow injection based on horseradish-catalysed luminol chemiluminescence. For reproducible determination of H(2)O(2) with HRP, the inactivation of HRP via protonation of the active sites of HRP caused by reaction with H(2)O(2) must be avoided. We successfully reactivated protonated HRP (inactive HRP) with exogenous imidazole in the mobile phase of the micro fl ow injection system. The imidazole successfully removed the attached proton from the inactive sites of the HRP. This assay was reproducible (within-run reproducibility, CV = 4.0%) and the detection limit for H(2)O(2) was 5 pmol.

Determination of organic peroxides by liquid chromatography with on-line post-column ultraviolet irradiation and peroxyoxalate chemiluminescence detection

A HPLC method was developed for the simultaneous determination of organic peroxides and hydrogen peroxide with peroxyoxalate chemiluminescence (PO-CL) detection following on-line UV irradiation. Organic peroxides [i.e., benzoyl peroxide (BP), tert.-butyl hydroperoxide (BHP), tert.-butyl perbenzoate (BPB), cumene hydroperoxide (CHP)] were UV irradiated (254 nm, 15 W) to generate hydrogen peroxide, which was determined by PO-CL detection. The conditions for UV irradiation and PO-CL detection were optimized by a flow injection analysis (FIA) system. Generation of hydrogen peroxide from peroxides with on-line UV irradiation also was confirmed by the FIA system by incorporating an enzyme column reactor immobilized with catalase. The separation of four organic peroxides and hydrogen peroxide by HPLC was accomplished isocratically on an ODS column within 30 min. The detection limits (signal-to-noise ratio=3) were 1.1 microM for hydrogen peroxide, 6.8 microM for BP, 31.3 microM for BHP, 7.5 microM for BPB and 1.3 microM for CHP. The proposed method was applied to the determination of BP in wheat flour.

Chemiluminescent determination of hydrogen peroxide with 9-acridinecarbonylimidazole and use in measurement of glucose oxidase and alkaline phosphatase activity

Several activated derivatives of 9-acridinecarboxylic acid were prepared in order to investigate their utility for detection of hydrogen peroxide. One of these derivatives, 9-acridinecarbonylimidazole (I), is especially stable and is a useful reagent for measuring, by chemiluminescence, the activity of a number of enzymes that directly produce peroxide, including glucose oxidase. Other enzymes can also be assayed if an appropriate intermediate substrate exists that ultimately produces hydrogen peroxide after being acted upon by the enzyme. 5-Bromo-4-chloro-3-indolyl phosphate (BCIP) and 3-indolyl phosphate (3-IP) are such substrates for alkaline phosphatase. The detection limits for both of these enzymes are in the 1-10 amol range. Other enzymes that can potentially be assayed using I include oxidases, hydrolases and dehydrogenases. Negative assays for compounds that consume or bind peroxide such as reducing agents, antioxidants, catalases and peroxidases are also feasible.