Simultaneous quantification of acetanilide herbicides and their oxanilic and sulfonic acid metabolites in natural waters.

This paper describes a procedure for simultaneous enrichment, separation, and quantification of acetanilide herbicides and their major ionic oxanilic acid (OXA) and ethanesulfonic acid (ESA) metabolites in groundwater and surface water using Carbopack B as a solid-phase extraction (SPE) material. The analytes adsorbed on Carbopack B were eluted selectively from the solid phase in three fractions containing the parent compounds (PCs), their OXA metabolites, and their ESA metabolites, respectively. The complete separation of the three compound classes allowed the analysis of the neutral PCs (acetochlor, alachlor, and metolachlor) and their methylated OXA metabolites by gas chromatography/mass spectrometry. The ESA compounds were analyzed by high-performance liquid chromatography with UV detection. The use of Carbopack B resulted in good recoveries of the polar metabolites even from large sample volumes (1 L). Absolute recoveries from spiked surface and groundwater samples ranged between 76 and 100% for the PCs, between 41 and 91% for the OXAs, and between 47 and 96% for the ESAs. The maximum standard deviation of the absolute recoveries was 12%. The method detection limits are between 1 and 8 ng/L for the PCs, between 1 and 7 ng/L for the OXAs, and between 10 and 90 ng/L for the ESAs.