Chiral pollutants derivatization

Besides the parameters discussed above, some other factors can also be used to optimize chiral resolution by CE. These parameters include the reversal of polarity, the volume of sample injected, the use of EOF modifiers and pre-derivatization of the chiral pollutants with a suitable reagent. In the normal CE machine, the anode (+) and cathode (—) are always at the inlet and outlet ends, respectively. In this modality, the EOF always tends to travel towards the cathode (detector). On the other hand, in the reverse mode, the direction of the EOF is away from the detector, and hence only negatively charged diastereomeric complexes with an electrophoretic mobility greater than the EOF will pass the detector. This format is typically used with capillaries that are coated with substances that reverse the net charge of the... 

Only a few reports are available in the literature dealing with the limits of the detection for the chiral resolution of environmental pollutants by CE, indicating mg/L to fig/L as the limits of the detection. Tsunoi et al. " carried out an extensive study on the determination of the limits of the detection for the chiral resolution of herbicides. The authors used a 230-nm wavelength for the detection and the minimum limit of the detection achieved was 4.7 X 10 M for 2,4-dichhophenoxy acetic acid. On the other hand, Mechref and El Rassi reported better detection limits, for herbicides, in the derivatized mode, in comparison to the underivatized mode. For example, the limit of the detection was enhanced by almost 1 order of magnitude from 1x10 " M (10 pmol) to 3 x 10 M (0.36 pmol). In the same study, the authors reported 2.5 X 10 M and 1 x 10 M as the limits of detection for the herbicides by fluorescence and laser-induced fluorescence detectors, respectively. 

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