ONLINE LIQUID-CHROMATOGRAPHIC TRACE ENRICHMENT AND HIGHPERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF DIQUAT, PARAQUAT AND DIFENZOQUATIN WATER

For the trace-level determination of diquat, paraquat and difenzoquat in drinking and surface water, a fully automated method using on-line trace enrichment, LC separation and UV detection is described. An auto matic sample preparation device (OSP-2, Merck) was employed as the sam ple preparation unit. The three herbicides were trapped from the flowi ng water sample by adsorption on a silica cartridge placed in a circul ar cartridge magazine, then the load cartridge was moved to the elutio n side. On the elution side, the herbicides were transferred to the an alytical column by the mobile phase. Detection limits for the three he rbicides below 20 ng/l were obtained after preconcentrating 200 ml of drinking water. The total analytical procedure was applied for the mon itoring of the three herbicides in drinking and surface water.