Environmental applications of chiral HPLC and development of new chiral stationary phases
Abstract
When a molecule is asymmetric (chiral), it can have a non-superposable mirror image, or enantiomer. Because organisms constitute an asymmetric (chiral) environment and most enzymatic pathways are stereoselective, organisms selectively metabolize and accumulate chiral compounds. Therefore, the biological activities and properties of the two enantiomers of a chiral pesticide are often different. About a quarter of pesticides on the market are chiral but a majority of them are sold as racemates, a 1:1 mixture of two enantiomers. Current regulations treat chiral pesticide mixtures as if they were only single compound. The U.S. Environmental Protection Agency (EPA) has not developed any method to analyze chiral pesticides in the environment. The Rio Grande Valley study unit of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program studied the occurrence and distribution of a total of forty pesticides and their metabolites in the surface water of the Mesilla Valley in New Mexico and Texas. Among those selected pesticides, seven are chiral. Again, this research ignored chirality in the entire analysis. This can lead to incorrect toxicological, distribution, and degradation data. To raise the awareness of the fact that enantiomers are not identical, this research was focused on developing methods to resolve chiral pesticides. High Performance Liquid Chromatography (HPLC) was used for this application. A commercial pharmaceutical analysis chiral method development kit was used to analyze six pesticide stereoisomer mixtures. The pesticides were selected from the 1994 NAWQA Program. Three pesticide stereoisomer mixtures were separable on three different columns. The instrumental detection limit and detection linear range of chiral HPLC of these analytes were determined. Combining SW-846 Method 3540C and chiral HPLC the efficient extraction (>86%) from soil of a chiral pesticide, Napropamide, was demonstrated. The difference in the degradation of the two enantiomers of Napropamide in soil was also studied. The asymmetric synthesis and enzymatic resolution of trans-2-(1-methyl-1-phenylethyl)cyclohexanol (TCC) and trans-2-(1-methyl-1-phenylethyl)-cyclohexylamine (TCCA) were both attempted with the goal of manufacturing new HPLC chiral stationary phases (CSP). The enantiorecognition of the CSPs was tested.
Subject Area
Environmental science|Organic chemistry|Analytical chemistry
Recommended Citation
Lee, Wen-Yee, "Environmental applications of chiral HPLC and development of new chiral stationary phases" (2000). ETD Collection for University of Texas, El Paso. AAI9997673.
https://scholarworks.utep.edu/dissertations/AAI9997673