|Lerch, Robert - Bob|
Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: 12/24/2002
Publication Date: 7/1/2003
Citation: LERCH, R.N., FERRER, I., THURMAN, E.M., ZABLOTOWICZ, R.M. IDENTIFICATION OF TRIFLURALIN METABOLITIES IN SOIL USING ION-TRAP LC/MS/MS. FERRER, I., THURMAN, E.M., EDITORS. AMERICAN CHEMICAL SOCIETY SYMPOSIUM SERIES 850; CHAPTER 17. 2003. P. 291-310 LIQUID CHROMATOGRAPHY/MASS SPECTROMETRY, MS/MS AND TIME-OF-FLIGHT MS. Interpretive Summary: Trifluralin (Treflan) has been one of the most heavily used herbicides for control of grasses, primarily in soybeans and cotton, since its introduction in the early 1960's. Trifluralin degradation in soils is complex, potentially resulting in the formation of 28 metabolites (i.e., breakdown products). Trifluralin degrades by different pathways depending upon the amount of oxygen in the soil atmosphere. Over the last 30 years, many studies were conducted to determine the fate of trifluralin in soils, but these studies did not clearly identify the most stable metabolites formed. Some of these metabolites have very different chemical properties than the parent compound, and they may significantly contaminate soils, sediments, and water. This research applied the most modern analytical instrumentation available to determine the stable trifluralin metabolites present in two soils collected from herbicide spill sites in Illinois. Preliminary results identified the presence of up to eight metabolites in the soils, and the array of metabolites present were indicative of aerobic (i.e., oxygen present) trifluralin degradation. One metabolite represents a potential contaminant in water, and at least two other metabolites are likely to persist in soils and to contaminate sediments in streams, lakes, and reservoirs of watersheds with current or historically heavy use of trifluralin. Further research will be conducted to determine if these metabolites do in fact represent important environmental contaminants. At this early stage in the research, the primary beneficiaries of this work are other scientists studying the environmental fate of herbicides. In the long run, the general public will benefit from a thorough evaluation of trifluralin fate in the environment and assessment of the potential public health threat represented by its stable metabolites.
Technical Abstract: Trifluralin degradation in soils is complex, potentially resulting in the formation of 28 metabolites. The objective of this research was to develop an approach for the identification of trifluralin metabolites in soils using ion-trap LC/mass spectrometry (ion-trap LC/MS/MS). Authentic standards of the parent and six metabolites were used to establish appropriate instrument conditions and precursor ion (PI) fragmentation patterns to confirm their identity, as well as to facilitate confirmation of metabolites for which authentic standards were not available. Two soils from herbicide spill sites known to be contaminated with trifluralin were selected for study because of their high potential for metabolite detection. Soils were extracted with 70% aqueous acetonitrile, filtered, and directly injected into the ion-trap LC/MS/MS. Trifluralin metabolites were then identified as follows: 1) screen for PI masses; 2) compare retention time of the PI peak to standards; and 3) obtain PI spectra and compare fragmentation with standards. The validity of this approach was confirmed for the identification of metabolite, TR-20. Preliminary results identified the presence of up to eight metabolites in the soils, and the array of metabolites present were indicative of aerobic trifluralin degradation.