ONLINE ISOTACHOPHORETIC SAMPLE PRETREATMENT IN ULTRATRACE DETERMINATION OF PARAQUAT AND DIQUAT IN WATER BY CAPILLARY ZONE ELECTROPHORESIS

Capillary zone electrophoresis (CZE) with on-line isotachophoretic (ITP) sample pretreatment ins column-coupling configuration of capillary electrophoresis equipment was studied from the point of view of (ultra)trace analysis of paraquat and diquat in water. Using this technique, a sample volume as large as 90 mu L can be accommodated and the herbicides can be analyzed with a detection limit of 10(-9) mol/L. A photometric absorbance detector was used operating at 310-nm wavelength. Adsorption losses of the pesticides on the walls of the sample containers were found to be main sources of analytical errors. They could be eliminated by spiking the samples with diethylenetriamine.