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1.
Jurva U Wikström HV Bruins AP 《Rapid communications in mass spectrometry : RCM》2002,16(20):1934-1940
Oxygen radicals are generated in vivo by various processes, often as toxic intermediates in different metabolic transformations, and have been shown to play an important role for a large number of diseases. In this article we introduce an electrochemical flow-through system that allows generation of hydroxyl radicals for reaction with xenobiotics and subsequent detection of the oxidation products on-line with high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). The system is based on the Fenton reaction and is predominantly aimed at the generation of hydroxyl radicals; however, by minor variations to the system, a broad range of other radicals can be produced. Optimization of the system was performed with the radical scavenger 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Under the same physical conditions, one injection through the electrochemical cell gave a higher yield of the oxidation product N-hydroxy-5,5-dimethylpyrrolidin-2-one than what was attained after 60 min with a chemical Fenton system catalyzed by ascorbic acid. Since the iron is added as Fe(3+), the initial mixture is 'inactive' until it reaches the electrochemical cell. This makes it very suitable for on-line analysis of the generated compounds, since the whole reaction mixture, including substrate, can be kept in a vial in an autosampler. The system described provides a useful tool for investigation of new radical scavengers and antioxidants. Since the hydroxyl radical adds readily to unsaturated pi-systems, the technique is also suitable for on-line generation and characterization of potential drug metabolites resulting from hydroxylation of double bonds and aromatic systems. 相似文献
2.
The site of proton abstraction by OH? ion in some 4-substituted-3,5,6-triphenyl-Δ′-cyclohexenes has been established from labelling studies. The further fragmentation mode of (M-H)? ion depends on its structure and stereochemistry. The and nitro isomers exhibit stereochemical differences in the elimination of HNO2 while the amino and cyano analogues show stereochemically controlled RDA fragmentation mode. 相似文献
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