MIXED-MODE ISOLATION OF TRIAZINE METABOLITES FROM SOIL AND AQUIFER SEDIMENTS USING AUTOMATED SOLID-PHASE EXTRACTION

Reversed-phase isolation and ion-exchange purification were combined in the automated solid-phase extraction of two polar s-triazine metabolites, 2-amino-4-chloro-6-(Isopropylamino)-s-triazine (deethylatrazine) and 2-amino-4-chloro-6-(ethylamino)-s-triazine (deisopropylatrazine) from clay-loam and silt-loam soils and sandy aquifer sediments. First, methanol/water (4/1, v/v) soil extracts wore transferred to an automated workstation following evaporation of the methanol phase for the rapid reversed-phase isolation of the metabolites on an octadecyl resin (C18). Tho retention of the triazine metabolites on C18 decreased substantially when trace methanol concentrations (1 %) remained. Furthermore, the retention on C18 increased with decreasing aqueous solubility and increasing alkyl-chain length of the metabolites and parent herbicides, indicating a reversed-phase interaction. The analytes were eluted with ethyl acetate, which left much of the soil organic-matter impurities on the resin. Second, the small-volume organic eluate was purified on an anion-exchange resin (0.5 mL/min) to extract the remaining soil pigments that could foul the ion source of the GC/MS system. Recoveries of the analytes were 75%, using deuterated atrazine as a surrogate, and were comparable to recoveries by soxhlet extraction. The detection limit was 0.1 Ag/kg with a coefficient of variation of 15 %. The ease and efficiency of this automated method makes It viable, practical technique for studying triazine metabolites in the environment.