Abstracts Submitted for the 34th Annual FACSS Meeting

Center for Analytical Spectroscopy students Jody Harvey and Selorm Modzabi have submitted their abstracts for the 34th annual Federation of Analytical Chemistry and Spectroscopy Societies meeting in Memphis, TN, October 14-18, 2007. Both abstracts can be seen below.

Chiral Ionic Liquids as Chiral Selectors for Chiral Analysis by Regression Modeling of Spectral Data: Effect of Concentration and Solvent

Jody A. Harvey, Marianna A. Busch, Kenneth W. Busch,

Most pharmaceutical products today contain molecules with chiral centers and it is now well established that two members of an enantiomeric pair can have different pharmacokinetic, pharmacological, and toxicological properties. This realization has led to the marketing of single-enantiomer drugs, and currently over 40% of all prescription drug sales are for single-enantiomer formulations. Consequently, the development of rapid-screening methods for determining enantiomeric purity is of major importance in pharmaceutical analysis, and spectroscopic methods are considered to be most desirable for this purpose. Our group has previously conducted research toward using multivariate regression modeling of spectral data (UV absorption or fluorescence) to determine the enantiomeric composition of a chiral analyte in the presence of chiral selectors like cyclodextrins. This technique is referred to as chiral analysis by regression modeling of spectral data (CARMSD). Due to the limitations of using cyclodextrins as chiral selectors, it was decided to explore the feasibility of using chiral ionic liquids (CILs) with the CARMSD technique to predict enantiomeric composition of analytical samples. CILs are potentially ideal for chiral discrimination because they can interact with other chiral molecules by a wide variety of intermolecular interactions. Previous studies in our laboratory have demonstrated that using a CIL as a chiral selector in solution can give similar results to those of beta-cyclodextrin. The effect of varying the concentration of CIL on the prediction ability of a regression model will be presented. In addition, the solvent dependence on the analyses will be discussed.

Selection of an Appropriate Chiral Selector for Chiral Analysis by Regression Modeling of Spectral Data

Selorm K. Modzabi, Marianna A. Busch, and Kenneth W. Busch

With the current emphasis in the pharmaceutical industry on single enantiomer drugs, there is a need for rapid analytical methods to assess the enantiomeric purity of emerging drugs. Recently, a new technique, known as chiral analysis by regression modeling of spectral data (CARMSD), has been developed by our group and used successfully to predict the enantiomeric composition of unknown samples of chiral analytes. With the CARMSD method, a fixed amount of chiral analyte is mixed with a fixed amount of some chiral auxiliary. Under these conditions, it is found that the UV-visible spectra of the solutions vary with the enantiomeric composition of the samples, and these spectral variations can be correlated with the enantiomeric composition of the samples by multivariate regression modeling. Once a multivariate regression model has been developed with a calibration set of samples, the mathematical model can then be used to predict the enantiomeric composition of future samples solely from their UV spectra. A key aspect of this approach is the selection of an appropriate chiral selector. A premise behind the CARSMSD approach is that the chiral selector associates in some way with the enantiomeric pair of the chiral analyte producing diastereomeric interactions that lead to small differences in the UV spectra of samples with different enantiomeric compositions. An ideal chiral selector would have a center of chirality as close as possible to the functional group involved in the association between the chiral analyte and the chiral selector so as to provide maximum diastereomeric effects. In addition, the chiral selector should be as rigid as possible to limit the number of possible conformations of the analyte/selector adduct. This paper will report our efforts in developing appropriate chiral selectors for CARSMSD that maximize the spectral differences in the UV spectra of the samples.

For further information on FACSS, visit their website: www.facss.org.

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