Mixed-Mode Isolation of Triazine Metabolites from Soil and Aquifer Sediments Using Automated Solid-Phase Extraction

By M.S. Mills and E.M. Thurman

Abstract

Reversed-phase isolation and ion-exchange purification were combined in the automated solid-phase extraction of two polar s-traizine metabolites, 2-amino-4-chloro-6-(isopropylamino)-s-trazine (deethylatrazine) and 2-amino-4-chloro-6-(ethyl-amino)-s-tranzine (deisopropylatrazine) from clay-loam and silt-loam soils and sandy aquifer sediments. First, methanol/water (4/1, v/v) soil extracts were transferred to an automated workstation following evaporation of the methanol phase for the rapid reversed-phase isolation of the metabolites on an octadecylresin (C₁₈). The 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 GS/MS system. Recoveries of the analytes were 75%, using deuterated atrazine as a surrogate, and were comparable to reciveries by soxhlet extraction. The detection limit was 0.1 &microg/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.

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Mills, M.S. and Thurman, E.M, 1992, Mixed-mode isolation of triazine metabolites from soil and aquifer sediments using automated solid-phase extraction [abst.]: Analytical Chemistry, v. 64, p. 1985-1990.

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