Analysis of Hydroxylated Atrazine Degradation Products in Soils

Abstract

Hydroxylated atrazine degradation products (HADPs) have been shown to persist in soils and contaminate surface waters throughout the Midwestern United States, yet expedient analytical methods for their determination in soils are lacking. The developed method employs a mixed-mode extractant [3:1 0.5M KH2PO4, pH 7.5:CH3CN, v/v] designed to disrupt the two primary mechanisms of HADP sorption to soils: cation exchange and hydrophobic interactions. Strong anion exchange solid-phase extraction (SPE) is used for sample clean-up followed by isolation and concentration using strong cation exchange SPE. HADPs were quantitated by LC/MS/MS and LC/UV. Method recoveries were determined by spiking 14C-HADPs into three soils with lengthy atrazine use histories. Recoveries ranged from 74–81% for 14C-hydroxyatrazine (HA), 79–88% for 14C-deethlhydroxyatrazine (DEHA), and 64–77% for 14C-deisopropylhydroxyatrazine (DIHA). HADP soil concentrations ranged from 66.9–178 μ kg−1 for HA, 8.99–40.9 μg kg−1 for DEHA, and 5.27–16.2 μg kg−1 for DIHA. Utilization of the mixed-mode procedure, in conjunction with existing methodologies for analysis of atrazine and its chlorinated metabolites, enables a more complete and accurate quantitation of all the major stable atrazine residues in soiis. HADPs comprised an average of 91% of the total atrazine residues in three agricultural surface soils, with HA the major constituent present in all soils. These data indicate that repeated atrazine use results in HADPs as the predominant atrazine residues in surface soils.