Analysis of bipyridylium herbicides by capillary zone electrophoresis.

The separation of paraquat, diquat, and difenzoquat bipyridilium herbicides and ethyl viologen as internal standard is shown. The separation has been carried out using a fused silica capillary with a high-sensitivity detection cell for a capillary electrophoresis system and with a diode array detector. The experiments have been performed using phosphate buffer 50 mM at pH = 4 and pH = 7. The effect of methanol has also been studied when used as an organic modifier. Different voltages and electrokinetic conditions have been used to optimize the separation. Twenty Kv voltage and 10 Kv for 3 sec for injection have been found to be reliable conditions of separation at pH 4 without organic modifier.