Analytical applications of circular dichroism: Use of color induction reactions for qualitative and quantitative analysis

Scope and method of study. Analytical applications of circular dichroism (CD) spectropolarimetry that are based on color induction reactions are presented. There are two approaches to color induction reactions for CD. In one case, a chromophore is added to an analyte that possesses native CD activity in order to induce a new CD spectrum that has, in effect, been shifted away from the high background UV absorbances. In the other case, the CD activity of the analyte may be weak and there can be significant analytical advantages to induction via a chiral chromophore. This approach retains all of the aforementioned advantages with the added potential for further increases in selectivity and sensitivity of the CD measurement.;Findings and conclusions. The above methods were applied to such diverse analytical problems as determining enantiomeric purities (EP) and isomeric purities (IP) of mixtures of enantiomers and/or diastereoisomers, obtaining quantitative and qualitative information on conformation of saccharides in solution, and providing qualitative information concerning monitoring of the biosynthesis of isoflavonoids. CD analysis of mixed complexes of Cu(II)-tartrate-ephedrine complexes combined with multivariate PLS2 analysis provided a superior method for the determination of EP or IP in binary mixtures. The calculation of formation constants for a series of dye-saccharide association complexes and the associated qualitative spectral information provided unique insight into the nature of dye-saccharide solution conformations. Additionally, the unique information inherent in CD spectra, whether native or induced, was shown to have considerable potential as an aid for recognition of intermediates in biosynthetic pathways for molecular biology.