TP6 Degradates in the Environment
202 Oregon Ballroom
1:20 PM - 4:40 PM, Tuesday
() Determination of Terbufos Sulfoxide in Surface- and Ground-Water Samples by Solid-Phase Extraction GC/MS using a Short (5-m) GC column.
Sandstrom, M1, Stroppel, M1, Blomquist, J2, Kanagy, C1, 1 U.S. Geological Survey (USGS), National Water Quality Laboratory, Denver, CO, USA2 U.S. Geological Survey (USGS), Baltimore, MD, USA
ABSTRACT- Terbufos is an organophosphate (OP) pesticide used for control of insects on corn and sorghum crops. It is ranked as one of the highest use OP pesticides in the United States in kilograms and hectares applied. During 1992-2001, terbufos was rarely found in surface-water samples collected in the U.S. Geological Survey National Water-Quality Assessment (NAWQA) program, with only 17 detections in 5,198 samples. Terbufos has two major degradation products, terbufos sulfone and terbufos sulfoxide. These degradates are more mobile and substantially more persistent in the environment than the parent terbufos. The persistence of these degradates is a concern because they have the same toxicity characteristics as the parent. The NAWQA monitoring data do not include these degradates, and this omission limits their use to other Federal agencies and data users for evaluating the fate of terbufos in the environment. We have modified and implemented a method to measure terbufos sulfoxide and terbufos sulfone, as well as other organophosphate pesticides and degradates, at nanogram-per-liter (ng/L) concentrations in filtered surface- and ground-water samples collected for the NAWQA program. Compounds are isolated from a 1-L water sample onto a 0.5-gram octadecyl bonded silica solid-phase extraction column and eluted with 2 mL of ethyl acetate. The extract is analyzed by gas chromatography (GC), using a short (5-m) column, with selected-ion monitoring mass spectrometry (SIM/MS) following solvent evaporation and exchange to toluene. The short column is essential for determination of terbufos sulfoxide because it prevents band broadening of the compound on the GC column. The method complements a previous method developed for the NAWQA program and currently (2004) is used for analysis of water samples collected in this and other national programs. The method was applied in the NAWQA study of surface- and ground-water samples collected from various locations in the United States during 2004.
Key words: degradate, pesticide, organophosphate