Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2000
Publication Date: 11/20/2000
Citation: POTTER, T.L., MARTI, L.R., BELFLOWER, S.C., TRUMAN, C.C. MULTI-RESIDUE ANALYSIS OF COTTON DEFOLIANT, HERBICIDE AND INSECTICIDE RESIDUES IN WATER BY SOLID-PHASE EXTRACTION AND GC-NPD, GC-MS AND HPLC-DIODE ARRAY DETECTION. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 48:4103-4108. 2000. Interpretive Summary: Cotton has made a "comeback" in the Southeast. No where is this more evident than in Georgia. Georgia farmers planted cotton on approximately 500000 acres in 1987. This had risen to more than 1400000 acres in 1997. This increase in the area under cultivation has increased the potential for water contamination with residues of pesticides and other crop-manage- ment chemicals. Modern cotton production practices require use of a wide- variety of products such as herbicides, insecticides, fungicides, plant growth regulators and chemical defoliants. In some circumstances, application rates are relatively high. These factors have contributed to the need to evaluate potential water quality impacts. This research has contributed to the need to evaluate potential water quality impacts. This research has contributed to that effort by developing a method which allows trace level analysis for the residues of many of the products used on cotton simultaneously. The method was needed to make water quality monitoring and research programs more efficient. Prior to the development of the method, analytical procedures which targeted some of the most widely used cotton pesticides and defoliants were not available. The test method significantly enhances the ability of agricultural research scientists and water quality specialists to systematically evaluate farming practices that will minimize adverse environmental impacts of cotton production.
Technical Abstract: A multi-residue procedure was developed for analysis of cotton pesticide and harvest-aid chemicals in water using solid-phase extraction and analy- sis by GC/NPD, GC/MS and HPLC-DAD. Target compounds included the defoliants, tribufos, dimethipin, thidiazuron; the herbicide, diuron and the insecticide, methyl parathion. Three SPE solid phases, octadecylsilyl (ODS), graphitized carbon black (GCB) and a divinylbenzene-N-vinyl pyrollidine co-polymer (DVBVP) were evaluated. On GCB and ODS recoveries varied depending on compound type. Recoveries were quantitative for all compounds on DVBVP, ranging from 87 to 115% in spiked deionized water and surface runoff. The method detection limit was less than 0.1 ug L**1. The SPE with DVBVP procedure was applied to post defoliation samples of surface runoff and tile drainage from a cotton research plot and surface runoff from a commercial field. The research plot was defoliated with a tank mixture of dimethipin and thidiazuron and the commercial field with tribufos. Dimethipin was detected (1.9 to 9.6 ug L**1) in all research plot samples. In the commercial field samples, tribufos concentration ranged from 0.1 to 135 ug L**1. An exponentially decreasing concentration trend observed with each successive storm event.