COUPLED-COLUMN LIQUID-CHROMATOGRAPHY APPLIED TO THE TRACE-LEVEL DETERMINATION OF TRIAZINE HERBICIDES AND SOME OF THEIR METABOLITES IN WATERSAMPLES

In the present work, a study is reported of the potential of coupled-c olumn liquid chromatography (LC) applied to the determination of triaz ine residues in environmental water samples. For this purpose, two dif ferent techniques have been compared: on-line trace enrichment followe d by LC (SPE-LC) and coupled-column liquid chromatography (LC-LC). Fir st, a completely automated liquid chromatographic method based on on-l ine trace enrichment in a prepacked precolumn and using diode array de tection has been developed for the simultaneous trace-level determinat ion of six triazine herbicides (simazine, cyanazine, atrazine, terbume ton, terbuthylazine, and terbutryn) and the main atrazine metabolites (desisopropylatrazine, desethylatrazine, and hydroxyatrazine), After p reconcentration parameters were optimized by testing two different sor bents (C-18 and PRP-1) in three cartridges with different dimensions, a sample volume of 100 mL was selected in order to achieve maximal sol ute preconcentration. Detection limits lower than 0.1 mu g.L-1 were ob tained even for the most polar analyte (desisopropylatrazine), which p resented recoveries of around 30%, The method was validated by means o f recovery experiments in groundwater and surface water samples spiked with the analytes at different levels (0.2-2 mu g.L-1). Afterward, th e procedure was successfully applied in a program for monitoring of tr iazine residues in surface water carried out in a ret area of Castello n, Spain. Different triazine herbicides such as simazine, terbumeton, terbuthylazine, and terbutryn were identified and quantified. The iden tity of these compounds was confirmed by their absorption UV spectra a nd by GC/MS analysis. Finally, two rapid, sensitive, and selective pro cedures, previously developed in our laboratory for the trace-level de termination of triazine compounds, both based on LC-LC, were compared with the former procedure, The SPE-LC approach showed a considerable i mprovement in the global sensitivity at the expense of a decrease in s electivity as well as in sample throughput.