Chlorophenoxy acid residues

Figure 13.11 Column-switcliing RPLC trace of a surface water sample spiked with eight chlorophenoxyacid herbicides at the 0.5 p-g 1 level 1, 2,4-dichlorophenoxyacetic acid 2, 4-chloro-2-methylphenoxyacetic acid 3, 2-(2,4-diclilorophenoxy) propanoic acid 4, 2-(4-cliloro-2-methylphenoxy) propanoic acid 5, 2,4,5-trichlorophenoxyacetic acid 6, 4-(2,4-dichlorophenoxy) butanoic acid 7, 4-(4-chloro-2-methylphenoxy) butanoic acid 8, 2-(2,4,5-tiichlorophenoxy) propionic acid. Reprinted from Analytica Chimica Acta, 283, J. V. Sancho-Llopis et al., Rapid method for the determination of eight chlorophenoxy acid residues in environmental water samples using off-line solid-phase extraction and on-line selective precolumn switcliing , pp. 287-296, copyright 1993, with permission from Elsevier Science.

J. V. Sancho-Llopis, F. Hernandez-Hernandez, E. A. Hogendoorn and P. van Zoonen, Rapid method for the determination of eight chlorophenoxy acid residues in environmental water samples using off-line solid-phase extraction and on-line selective precolumn switching , Anal. Chim. Acta 283 287-296(1993). 

The first section of this book describes the application of LC/MS to the analysis of agricultural chemicals and their metabolites. Using LC/MS for residue analysis in agricultural chemistry has become routine in many laboratories. Many pesticides, such as the chlorophenoxy acid and sulfonyl urea herbicides or organophosphorus and methyl carbamate insecticides, are too polar or thermally labile for analysis via GC. The use of LC/MS for the identification of polar pesticide metabolites and conjugates, an area traditionally dominated by radiolabeled compounds, stands out as a particularly dramatic demonstration of the power of this technique. 

Hopper, M.L. 1987. Methylation of chlorophenoxy acid herbicides and pentachlo-rophenol residues in foods using ion-pair alkylation. /. Agric. Food Chem. 35 285-289. 

A mixture of 22 grams of Oi-(p-chlorophenoxy)isobutyric acid, 3.8 grams of 1,3-propane-dioi, 0.5 gram of p-toiuenesulfonic acid and 150 ml of xylene was refluxed. When the theoretically calculated amount of water had been removed, the xylene solution was washed with dilute aqueous sodium bicarbonate and then the xylene was distilled off. The residue was distilled under reduced pressure to give 11 grams (47% yield) of 1,3-propanediol bis[a-(p-chlorophenoxy)isobutyrate] boiling at 197° to 200°C/0.03 mm Hg. 

In 1 L of water there is dissolved 116.0 g (1 mole) of N,N-diethylethylenediamine and, under vigorous stirring at a temperature maintained below 50°C, there is added 205.0 g (1 mole) of the chloride of p-chlorphenoxyacetic acid. The solution becomes rapidly homogeneous the formation of the basic amide hydrochloride is rapidly completed by further stirring the reaction mixture for 2 h at about 20°C. Then an excess of soda lye is added and the basic amide formed is extracted by ether. The ethereal solution is dried on anhydrous sodium sulfate and ether is distilled after that the residue is dried. So 2-(p-chlorophenoxy)-N-(2-(diethylamino)ethyl) acetamide is obtained. 

Humic acids of different origin and nature show a different interacting power in the homolytic reaction with chlorophenoxy residues, the average order of reactivity resulting synthetic-HA > peat-HA > soil-HA coal-HA > compost-HA. The only HA-molecular parameters which appear to correlate with this order of reactivity are the COOH content and the COOH/phenolic OH ratio. It results that the higher the values of these 2 parameters in the original HA, the lower its reactivity, measured as residual free spin percentage in the interaction products. 

Butz, S. Stan, H.-J. Determination of chlorophenoxy 23. and other acidic herbicide residues in ground water by capillary GC of their alkyl esters formed by rapid derivatization using various chloroformates. J. Chromatogr. 24. 1993, 643, 111-13%. 

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