Chiral pollutants

I. Ah, H.Y. Aboul-Enein, Chiral pollutants Distribution, toxicity and analysis by chromatography and capillary electrophoresis, Chichester, UK John Wiley Sons (2004). 

Chirality has been used to distinguish among sources of chiral pollutants to environmental compartments, such as the atmosphere or natural water bodies. Because partitioning processes between environmental media (e.g. deposition, volatilization) are physical processes, they are not likely to be enantioselective. Thus, if the enantiomer compositions of a chiral pollutant differ among environmental compartments, then a comparison of enantiomer signatures of different compartments can help to identify pollutant sources. The contribution of two sources to the environmental compartment of interest can be assessed quantitatively [303] ... 

Lewis, D.L. Garrison, A.W. Wommack, E. Whittemore, A. Steudler, R MeUllo, J., Influence of environmental changes on degradation of chiral pollutants in soils Nature 1999, 401, 898-901. 

Fisk, A.T. Holst, M. Hobson, K.A. Duffe, J. Moisey, J. Norstrom, R.J., Persistent organo-chlorine contaminants and enantiomeric signatures of chiral pollutants in ringed seals Phoca hispida) collected on the east and west side of the Northwater Polynya, Canadian Arctic Arch. Environ. Contain. Toxicol 2002, 42, 118-226. 

Advances in Chiral Pollutants Analysis by Capillary Electrophoresis... 

As in the case of chromatography, a chiral selector is also required in CE for enantiomeric resolution. Generally, suitable chiral compounds are used in the background electrolyte (BGE) as additives and hence are called chiral selectors or chiral BGE additives. There are only a few publications available that deal with the chiral resolution on a capillary coated with the chiral selector in CE. The analysis of the chiral pollutants discussed in this chapter is restricted only to using chiral selectors in the BGE. The most commonly used chiral BGE additives are cyclo-dextrins, macrocyclic glycopeptide antibiotics, proteins, crown ethers, ligand exchangers, and alkaloids.A list of these chiral BGE additives is presented in Table 1. 

Capillary electrophoresis has been used for the analysis of chiral pollutants, e.g., pesticides, polynuclear-aromatic hydrocarbons, amines, carbonyl compounds, surfactants, dyes, and other toxic compounds. Moreover, CE has also been utilized to separate the structural isomers of various... 

Normally, the chiral pollutants in the environment occur at low concentrations and therefore a sensitive detection method is essential and is required in chiral CE. The most commonly used detectors in the chiral CE are UV, electrochemical, fluorescence, and mass spectrometry. Mostly, the detection of the chiral resolution of drugs and pharmaceutical in CE has been achieved by a UV mode and therefore the detection of the chiral pollutants may be achieved by the same method. The selection of the UV wavelength depends on the type of buffer, chiral selector, and the nature of the environmental pollutants. The concentration and sensitivity of UV detection are restricted insofar as the capillary diameter limits the optical path length. It has been observed that some pollutants, especially organochloro pesticides, are... 

Chiral pollutants Sample matrix Electrolytes Detection Refs. 

Today, chromatographic modalities are used frequently for the analysis of chiral pollutants. The wide application of HPLC is due to the development of various chiral stationary phases and excellent reproducibility. However, ... 

Analysis of the chiral pollutants at trace levels is a very important and demanding field. In recent years, capillary electrophoresis has been gaining importance in the direction of chiral analysis of various racemates. A search of the literature cited herein indicates a few reports on the chiral resolution of environmental pollutants by CE. It has not achieved a respectable place in the routine chiral analysis of these pollutants due to its poor reproducibility and to the limitations of detection. Therefore many scientists have suggested various modifications to make CE a method of choice. To achieve good reproducibility. 

In addition, some other aspects should also be addressed so that CE can be used as a routine method in this field. The most important points related to this include the development of new and better chiral selectors, detector devices, and addition of a cooling device in the CE apparatus. In addition, chiral capillaries should be developed and the CE device should be hyphenated with mass spectrometer, polarimetric, and circular dichroism detectors, which may result in good reproducibihty and improved limits of detection. The advancement of CE as a chiral analysis technique has not yet been fiilly explored and research in this direction is currently underway. In summary, there is much to be developed for the advancement of CE for the analysis of chiral pollutants. It is hoped that CE will be recognized as the technique of choice for chiral analysis of the environmental pollutants. 

Aboul-Enein, H. Y, Ali, I. Analysis of the chiral pollutants by chromatography, Toxicol. Environ. Chem., 2004, 86, 1-22. 

Previous sections have illustrated the complexity of most of the compound-specific analyses developed in the environmental field. It is easy then to figure out that the accurate determination of a possible enantiomeric enrichment of chiral pollutants is even more difficult owing to the many co-elution problems and low concentration levels of the analytes. This difficulty could explain the somehow limited research conducted on this topic. However, its interest is clear. Industrial contaminants, such as PCBs or toxafene, are released into the environment as racemates. Therefore, a nonracemic composition of these pollutants might be evidence of selective biotransformation and/or bioaccumulation. Some studies have also pointed to different biological and toxic behaviour for each of the enantiomers [56], something that can be especially relevant for pesticides exhibiting chiral properties. 

Table 4 Selected GCxGC applications involving the analysis of chiral pollutants. For simplicity, only optimised experimental set-ups or those providing the most conclusive results have been mentioned (Acronyms as in Table 1)... 

Finally, in the electrolyte design during chiral pollutants method development, a chiral selector must always be considered. Cyclodextrins are among the most commonly used chiral additives and can be employed in both EKC and CZE methodologies, depending on the nature of the pollutant. 

Analysis of chiral pollutants by capillary electrophoresis (CE) is a new trend in separation science. This entry describes separation and identification of chiral xenobiotics by using CE. Attempts have been made to describe types of chiral selectors, applications, optimization of separations, detection strategies, mechanisms of chiral separations, CE vs chromatography and sample preparation methods. 

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