SEPARATION OF 18 MODERN PLANT PROTECTANTS USING CYCLODEXTRIN MODIFIEDMICELLAR ELECTROKINETIC CHROMATOGRAPHY INCLUDING AN ION-PAIRING REAGENT

A cyclodextrin-modified micellar electro kinetic chromatography separa tion for 18 different pesticides (metsulfuron-methyl, rimsulfuron, thi fensulfuron-methyl, desethylatrazine, desisopropylatrazine, atrazine, simazine, terbuthylazine, 2,4-D, MCPP, MCPB, dicamba, linuron, alachlo r, metolachlor, orbencarb, propiconazole, prochloraz) from eight diffe rent substance classes with very varying chemical and physical propert ies is presented. In particular acid base characteristics and water-oc tanol distribution coefficients diverge in wide ranges. beta-cyclodext rin was successfully employed as a modifier in separating the hydropho bic analytes. Peak distortion of some neutral analytes, which is devot ed to the methanol content of the sample zone, was reduced by increasi ng the SDS concentration. Methanol in the sample is necessary for a be tter solubility of the hydrophobic pesticides. Few optima of SDS conce ntration exist allowing the separation of sulfonylureas as well as phe noxy acids and hydrophobic pesticides. An improved resolution of the s ulfonylureas was achieved with tetramethylammonium chloride, which was used as an ion-pairing reagent. Final operating conditions for the se paration of all these plant protectant compounds by MEKC in just one s ingle run are a 27 mmol L-1 phosphate buffer, pH 8.03, with 95 mmol L- 1 SDS, 5 mmol L-1 beta-cyclodextrin and 10 mmol L-1 tetramethylammoniu m-chloride.