Author

Qingping Liu

Document Type

Thesis - University Access Only

Award Date

1996

Degree Name

Master of Science (MS)

Department

Chemistry and Biochemistry

Abstract

Chlorsulfuron, metsulfuron methyl, chlorimuron ethyl, thifensulfuron methyl and sulfometuron methyl are five of the most commonly used sulfonylurea herbicides. These herbicides are characterized by their high herbicidal activity, which results in very low application rates (10-40 g/ha). Therefore, a method for residue determination of these sulfonylurea herbicides must be very sensitive. An analytical method based on the use of capillary gas chromatography and mass spectrometry (GC-MS) with Selected Ion Monitoring (SIM) for determination of these sulfonylurea herbicides in soil and plant samples is described. Methylation of chlorsulfuron and thifensulfuron methyl by diazomethane in ethyl acetate produced N, N-dimethyl derivatives as the major products which were thermostable and could be analyzed quantitatively at low ppb levels. Methylation of chlorimuron ethyl, metsulfuron methyl and sulfometuron methyl by diazomethane produced N-monomethyl derivatives as the predominant products; these derivatives were not stable to GC-MS conditions, forming the rearranged N-methyl sulfonamides, which could be also analyzed quantitatively at low ppb levels. Soil samples were extracted with 0.1 M sodium hydrogen carbonate, and the extracts were cleaned up using Cl8 extraction disks or methylene chloride. Plant samples were extracted with 0.1 M sodium hydroxide, and the methylene chloride extracts were cleaned up on a Florisil column. GC-MS SIM parameters have been modified to optimize sensitivity. Chlorsulfuron and thifensulfuron methyl could be detected at 0.5 ppb and 1 ppb in soil samples, and at 4 ppb and 40 ppb in plant samples, respectively. Both metsulfuron methyl and chlorimuron ethyl could be detected at 1 ppb in soil samples. Metsulfuron methyl, chlorimuron ethyl and sulfometuron methyl could be detected at the 40 ppb level in plant samples.

Library of Congress Subject Headings

Soils -- Herbicide content

Plants, Effect of herbicides on

Gas chromatography

Mass Spectrometry

Format

application/pdf

Number of Pages

66

Publisher

South Dakota State University

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