Current Organic Chemistry - Volume 6, Issue 1, 2002

The possibilities offered by chemiluminescence (CL)-based analytical techniques apparently still remain unfamiliar to the average analytical researcher. Some of the advantages are that only minimal analytical instrumentation is required and because no external light source is needed, the optical system is quite simple. Hence strong background light levels are excluded leading to improved detection limits by this so-called dark-field technique. CL is observed in solid-, gas- and liquid-phase reactions and all have been used analytically. In solution, the most frequently used systems involve the organic reagents luminol and its derivatives, acridinium esters, lophine, peroxyoxalates, etc. Many important applications have been established in recent years for the determination of organic compounds, biomolecules, drugs and carcinogenics in a variety of environmental and clinical matrices. As in fluorescence detection, by applying derivatization techniques it is possible to convert a mole cule, which does not possess the ability to participate in a CL system, into another specie featuring this property. The rapid development of immobilization techniques has considerably enhanced the applications of CL, especially in flow injection analysis (FIA), in immunoassay and in the development of CL-based sensors. Also, the combination of CL-based detection employing prior separation methodologies such as high performance liquid chromatography (HPLC) or capillary electrophoresis (CE) has proved to offer promising analytical possibilities, providing excellent analytical sensitivity and selectivity, and allowing the resolution and quantification of various analytes in a complex mixture. This review intends to show general principles and characteristics of the technique which make it very useful in organic analysis.

This account focuses on the application of uv-vis and ir spectroelectrochemistry in the characterization of organic and related metal-organic molecules, from the point of view of their electrochemical and redox properties. Special emphasis has been given to the elucidation of multiple or successive redox processes. The scope has been limited to systems such as porphyrins, iron-amines, macrocycles and supramolecular porphyrins, spanning the last 15 years not covered by previous review articles on the subject.

The implementation of both the directly and the inversely detected 15N NMR techniques at the natural abundance level of the 15N isotope is demonstrated for a diverse array of structural problems in organic chemistry. Following the application of 15N NMR to the elucidation of the structures of natural compounds and synthetic products, the 15N-detected electron distribution in such molecules and following their reactions with other molecules and ions is discussed. A significant part of the 15N structural analysis is devoted to the description of tautomers, rotamers, conformers, configurational isomers, and regioisomers. The changes in the 15N parameters induced in structurally related compounds are described briefly. At present, the optimum probe-tube-sample configuration makes it possible to acquire inverse-detected 1H-15N correlation spectra on samples, where the total available sample is limited to amounts of < 1 mg (for molecules < 1000 Da and magnetic fields > 400 MHz). 15N NMR spectroscopy at the natural abundance level of 15N nuclei has become a powerful tool which has substantially extended the analytical arsenal of organic chemists.