6. Chiral pesticide analysis

Analytical methods are needed to identify the different stereoisomers and measure the concentration of each in residues that may be found in food and the environment. High-performance liquid chromatography (HPLC) equipped with chiral-phase columns is the most appropriate and widely used technique for this purpose.

Wrongly, the maximum residue limits set by regulations only exceptionally distinguish between stereoisomers, although we have seen that they almost always have different toxicities. It is therefore not irrelevant whether the residue of a mixture of two enantiomers consists of 90% of the more toxic enantiomer or 90% of the other. What's more, diastereomers generated by metabolic epimerization, under the effect of chemical agents or light, may have formed and proved even more toxic.

On the other hand, since diastereomers have different...