Herbicides, determination

L.J. Krutz, A.A. Senseman and A.S. Sciumbato, Solid-phase microextraction for herbicide determination in environmental samples. J. Chromatogr.A 999 (2003) 103-121. 

Much of the early work in characterizing the environmental behavior of chemicals was accomplished in the area of agricultural chemistry. Work surrounding the behavior of plant nutrients in the soil has provided a large base of information about the processes of environmental chemistry. Workers investigating the effectiveness of soil-applied herbicides determined that the herbicidal activity of organic chemicals varied with soil properties. It was determined that clay and OM contents of the soil were related to the ability of a soil to diminish the effectiveness of an organic herbicide applied [17,21]. 

Paschke, A., Neitzel, P.E., Walther, W., and Schiirmann, G. Octanol/water partition coefficient of selected herbicides determination using shake-flask method and reversed-phase high-performance liquid chromatography, J. Chem. Eng. Data, 49(6) 1639-1642, 2004. 

Also, the choice of resistance mutation(s) must be made in conjunction with the choice of herbicide(s). For the current example, corn without resistance alleles is highly sensitive to imazaquin and sulfometuron methyl, but has some natural tolerance for imazethapyr (Table II). A 7.5X increase in resistance would provide safety to postemergence applications of imazethapyr, whereas the corresponding increased resistance needed for safe applications of imazaquin would be 120X. Thus, the natural tolerance of a crop for a herbicide determines the level of resistance needed to use that herbicide on the crop. 

Boyd-Boland and Pawliszn reported the first application of SPME to the analysis of herbicide residues in 1995, for the simultaneous determination of nitrogen-containing herbicides in soU, water, and wine samples.Herbicides have been extracted following the three extraction modes (DI, HS, and in-tube), but direct insertion mode was the most used for these compounds. Krutz et al. have recently published an exhaustive review dealing with SPME for herbicide determination in environmental samples. 

Some examples of herbicide determination in water by SPME are presented in Table 26.4. 

As mentioned before, analytical methods required for herbicide determination must be very sensitive, selective, and robust. Normalized methods generally use liquid and gas chromatography techniques with detectors more or less specific. Sample pretreatment such as derivatization steps or cleanup of the extracts are sometimes mandatory prior to analytical measurement. 

Maizels, M. and Budde, W. L., Exact mass measurements for confirmation of pesticides and herbicides determined by liquid chromatography/time-of-flight mass spectrometry. Anal. Chem., 13, 5436-5440, 2001. 

The increasing complexity of the chemicals used as herbicides determines the development of more selective and accurate methods of analysis. Basically, analytical aspects related to herbicides should focus on five main directions (1) quality control of herbicide formulations during production and marketing ... 

Sodium-N-diethyldithiocarbamate, determination of 207 Stilbenzene, determination of 263, 264 Substituted urea herbicides, determination of 314-316 Succinate, determination of 60-65 Sulphate, determination of 51-56, 60-65, 70-75, 77, 87-90,170,199,... 

Sulphide, determination of 58,59, 77-79, 82, 85, 86,208,218,406,413 Sulphite, determination of 219 Sulphonated polyphenols, determination of 205 p-Sulphonyl carboxy salts, determination of 202 Sulphonylurea herbicides, determination of 182,183,186... 

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