Herbicide assays

Haupt K, Mayes AG, Mosbach K. Herbicide assay using an imprinted pol3mier-based system analogous to competitive fluoroimmunoassays. Anal Chem 1998 70 3936-3939. 

Table. II. Results of in vitro herbicide assay for seven tripeptide analogs...

The systemic morpholine fungicide Corbel with fenpropimorph as its active substance is frequently applied to cereal cropping. It is rapidly metabolized in soil to fenpropimorphic acid. For the assay of fenpropimorphic acid in soil, GC-MS coupling109 has been proposed. The GC technique was used to assure the best separation for the fenpropimorphic acid from the complex soil matrix. The MS technique is very sensitive and assures the best reliability of the analytical information. The same reliability is also achieved when the HPLC-MS tandem system is used for sulfonylurea herbicide assay in soil.110... 

R.O. Harrison, M.H. Goodrow, B.D. Hammock, Competitive Inhibition ELISA for the s-Triazine Herbicides Assay Optimization and Antibody Characterization , /. Agric. Food Chem., 39,122-128 (1991). 

Figure 7.10. Standard curves for 2,4-dichlorophenoxyacetic acid (2,4-D).Displacement of CMMC from the 2,4-D-imprinted MIP by 2,4-D (I), CPOAc ( ) and POAc (A) in a) 20 mM phosphate buffer, pFf 7, 0.1% Triton X-100 b) acetonitrile. Reprinted with permission from Haupt K, Mayes AG, Mosbach K. Herbicide assay using an imprinted polymer-based system analogous to competitive fluoroimmunoassays. Anal Chem 1998 70 3936-3939. 1998 American Chemical Society...

Sevin. 1-Naphthalenol methylcarbanate [63-25-2] (Sevin) (44) was developed as an insecticide. However, the conception of the molecule, in the mid-1950s, was as a possible herbicide. The compound ultimately was useless as a herbicide, but in routine testing it was discovered to be an excellent insecticide. Sevin was active in the oat mesocotyl assay and demonstrated weak auxin-like activity. During the development of Sevin, it caused massive apple drop in the western United States in an orchard being treated for insects. It is used (ca 1993) as an abscising agent to thin apples. 

A method of detecting herbicides is proposed the photosynthetic herbicides act by binding to Photosystem II (PS II), a multiunit chlorophyll-protein complex which plays a vital role in photosynthesis. The inhibition of PS II causes a reduced photoinduced production of hydrogen peroxide, which can be measured by a chemiluminescence reaction with luminol and the enzyme horseradish peroxidase (HRP). The sensing device proposed combines the production and detection of hydrogen peroxide in a single flow assay by combining all the individual steps in a compact, portable device that utilises micro-fluidic components. 

This third part of the book will be devoted mainly to the problem of addressing complex pollution problems and how they can be studied employing new biomarker assays that exploit new technologies of biomedical science. Chapter 13 will give a broad overview of this question. The following three chapters, The Ecotoxicological Effects of Herbicides, Endocrine Disrupters, and Neurotoxicity and Behavioral Effects, will all provide examples of the study of complex pollution problems. 

The following brief account identifies only major groups of herbicides not mentioned elsewhere in the text, and is far from comprehensive. Their mode of action is only dealt with in a superficial way. From an ecotoxicological point of view, there has not been as much concern about their sublethal effects upon plants as there has been in the case of mammals, and there has not been a strong interest in the development of biomarker assays to establish their effects. The major concern has been whether weeds, or nontarget plants, have been removed following herbicide application—a rather easy matter to establish as plants are fairly sedentary. For a more detailed account of herbicide chemistry and biochemistry, see Hassall (1990). 

This far into a nitrosamine symposium it should hardly be necessary to point out that nitrosamines are technically just one of a group of Ji-nitroso compounds that also includes nitros-amides, nitrosocarbamates, nitrosoureas, etc. Or that nitrosa-table pesticides encompass all the categories just mentioned and more. Or that many diverse pesticides, including herbicides, insecticides, and fungicides have been converted to Ji-nitroso derivatives in the laboratory (a recent review contained a 3-page, probably incomplete, compilation), or that some of the Ji-nitroso compounds thus synthesized were determined to be carcinogenic in test animals or mutagenic in various assays. 

Structurally related compounds may cross-react with the antibody, yielding inaccurate results. In screening for the herbicide alachlor in well water by immunoassay, a number of false positives were reported when compared with gas chromatography (GC) analysis. A metabolite of alachlor was found to be present in the samples and it was subsequently determined that the cross-reactivity by this metabolite accounted for the false-positive results. On the other hand, cross-reactivity by certain structural analogs may not be an issue. For example, in an assay for the herbicide atrazine, cross-reactivity by propazine is 196% because of atrazine and propazine field use... 

J. Strahan, Development and application of an enzyme-linked immunosorbent assay method for the determination of multiple sulfonylurea herbicides on the same microwell plate, in Environmental Immunochemical Methods, ed. J.M. Van Emon, C.L. Gerlach, and J.C. Johnson, American Chemical Society, Washington, DC, pp. 65-73 (1996). 

Because of the possibility that the herbicide alachlor could adulterate food if either poultry or livestock consumed contaminated materials, Lehotay and Miller evaluated three commercial immunoassays in milk and urine samples from a cow dosed with alachlor. They found that milk samples needed to be diluted with appropriate solvents (1 2, v/v) to eliminate the matrix effect. One assay kit (selected based on cost) was also evaluated for use with eggs and liver samples from chickens. Egg and liver samples were blended with acetonitrile, filtered, and diluted with water. Linear calibration curves prepared from fortified egg and liver samples were identical... 

Results presented in Table VII show that sufficient light is needed for new shoot formation on explants and that the herbicide fluridone causes chlorosis in new growth just as in whole plants (12,13). These data also confirm that the apical explant, which contains the terminal meristem, is a poor system for assaying inhibitors of new shoot production. 

Atrazine, used as a selective pre- and post-emergence herbicide to control annual weeds in several crops, is the most representative compound of this group. It is also used as a non-selective herbicide in non-crop areas. After absorption, the compound is metabolized to dealkylated and deisopropy-lated derivatives. The unchanged compound and its metabolites are excreted in urine, where they can be detected by chromatography or enzyme-linked immunosorbent assay (Lucas et al., 1993). A mercapturic acid conjugate of atrazine has also been found in urine samples of workers spraying this herbicide (Lucas et al., 1993) (Table 6). 

Automated online SPE LC systems are used extensively for environmental assays. Trays of SPE cartridges and autosampler can be used in the field. Water samples are preconcentrated trays of SPE cartridges loaded with analytes are brought to the laboratory and mounted onto an online SPE LC/ MS/MS system for analysis. Prospekt and Symbiosis systems were used for monitoring herbicides and transformation products (Hogenboom et al. 1998,1999a and b Lopez-Roldan et al. 2004 Kato et al. 2003 Lacorte and Barcelo 1995 Ferrer and Barcelo 1999,2001 Riediker et al. 2002), phenols... 

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