Phenoxy acetic acid herbicides

These workers [20] also examined thin layer chromatography of 2,4-DP (Dichloroprop) and MCPP (mixture of Mecoprop and 2-(2-chloro-4-methylphenoxy)propionic acid). In this method the ethyl ether extract of the sample is purified on a column of silicic acid and the herbicides are separated by thin layer chromatography on silica gel-kieselguhr (2 3) with light petroleum-acetic acid-kerosene (10 1 2) as solvent. The sensitivity is 3pg of either compound per litre, the average recoveries of Dichlorprop and MCPP are 85.7% and 87.4%, respectively, and the corresponding standard deviations were 13.9% and 15.5%. 

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This technique has also been coupled with mass spectrometry for the partial identification of organic compounds eluted from the column, e.g. the determination of phenoxy acetic acid herbicides in soil and non-saline sediments. 

Renberg [35] used an ion-exchange technique for the determination of chlorophenols and phenoxy acetic acid herbicides in soil. In this method the soil extracts are mixed with Sephadex QAE A-25 anion exchanger and the adsorbed materials are then eluted with a suitable solvent. The chlorinated phenols are converted into their methyl ethers and the chlorinated phenoxy acids into their methyl or 2-chloroethyl esters for gas chromatography. 

Isolation and trace enrichment in off-line and on-line modes were described together with TSP-LC-MS determination of the spiked phenoxy acetic acid herbicides 2,4-dichlorophenoxy acetic acid (2,4-D), 4-chloro-2-methylphenoxy acetic acid... 

The answer is 3 [Chapter 28 tE 2c). The phenoxy acetic acid herbicides (e.g., 2,4-D) are plant hormones that cause changes in plant metabolism. Both er hancement of palpability and increases In toxin content (e.g., nitrates) have been demonstrated for some toxic plants treated with these herbicides. The other classes of heriMCkles also alter plant metabolism, but do not seem to affect toxin content or the response of animals to poisonous plants. 

C. Timchalk, Comparative inter-species pharmacokinetics of phenoxy-acetic acid herbicides and related organic acids evidence that the dog is not a relevant species for evaluation of human health risk. Toxicology, 2004,200,1-19. 

Phenoxy acetic acid herbicides Phenoxyacetic acid, MCPA, dichloropro-pmecoprop 2,4-D, 2,4-dichlorophen-oxyacetic acid 2-(2,4,5-trichloro-phenoxy)propionic acid... 

In sludge anionic and non-ionic surfactants carboxylic acids hhydroxybutyrate hydroxy valerate chloroaliphatic compounds chlorophenols polychlorobiphenyls 4-nitrophenol mixtures of organic compounds chlorinated insecticides, phenoxy acetic acid type herbicides and organotin compounds. 

Another growing technique is super-critical fluid chromatography. Recent references to soil analysis include the following applications aliphatic hydrocarbons, polyaromatic hydrocarbons, polychlorobiphenyls, dioxins, alkyl and aryl phosphates, chloro, organophosphorus, triazine, substituted urea, phenoxy acetic acid, Dacthal herbicides and insecticides and mixtures of herbicides and pesticides and mixtures of organic compounds. 

Chau and Terry [146] reported the formation of penta-fluorobenzyl derivatives of ten herbicidal acids including 4-chloro-2-methyl-phenoxy acetic acid [145]. They found that 5h was an optimum reaction time at room temperature with pentafluorobenzyl bromide in the presence of potassium carbonate solution. Agemian and Chau [147] studied the residue analysis of 4-chloro-2-methyl phenoxy acetic acid and 4-chloro-2-methyl phenoxy butyric acid from water samples by making the pentafluorobenzyl derivatives. Bromination [148], nitrification [149] and esterification with halogenated alcohol [145] have also been used to study the residue analysis of 4-chloro-2-methyl phenoxy acetic acid and 4-chloro-2-methyl phenoxybutyric acid. Recently pentafluorobenzyl derivatives of phenols and carboxylic acids were prepared for detection by electron capture at very low levels [150, 151]. Pentafluorobenzyl bromide has also been used for the analytical determination of organophosphorus pesticides [152],... 

Waliszewski and Szynczynski [158] have described a gas chromatographic method for the determination of 4-chloro-2-methyl phenoxy acetic acid (MCPA) and 2.4 chloro phenoxy acetic acid (2.4D) herbicides in soils. The chlorophenoxy acetic acid herbicides were extracted from soil... 

Since the same effects occurred with the non-herbicidal (2,6-dichloro-phenoxy) acetic acid as with toxic compounds, glucose metabolic changes are not the important singular effects of auxin herbicides. 

Many other compounds have been included in studies on sucrose response. Most of these have been herbicides or enzyme poisons. None of the common herbicides had any positive effect on sucrose at rates up to that causing severe foliar injury. Earlier reports of response from 2-(2,4,5-trichlorophenoxy)propionic acid and 2,2-dichloropropionic acid could not be substantiated in British Guiana and Queensland. 27 Some compounds, such as 3-(p-chlorophenyl)-l,l-dimethylurea (monuron), (2,4-dichloro-phenoxy) acetic acid in soil, ethylenediaminetetraacetic acid, and leaf desiccants decreased sucrose and juice solids content. 20 Field trials with several chemicals in Trinidad showed enhanced sucrose at 14 to 28 days before harvest resulting from the application of 8 and 12 lb. (per acre) of... 

Dichloro-phenoxy acetic acid, 2,4,5- trichlorophenoxy acetic acid Herbicide derivatised to its methyl or 2-chlororethyl ester, then gas chromatography. 70 - 74% recovery [169]... 

See also Chlorophenoxy Herbicides 2,4-D (2,4-Dichioro-phenoxy Acetic Acid) Pesticides Poiiution, Water. 

Torstenson et al. (1975) published a nice example of adaptation of microflora to (2-methyl-4-chlorophenoxy) acetic acid (MCPA) and (2,4-dichloro-phenoxy) acetic acid (2,4-D). Soils from lots that had been treated with herbicides for 18, 1, and 0 (controls) years were used to inoculate a salt medium where 2,4-D or MCPA had been added as the carbon source (100 pM). The lag time before the degradation started was very much influenced by the type of inoculate, as shown by Figure 8.6 with data from Torstensson s work. 

Forgacs, E., Cserhati, T., and Barta, I., The binding of amino acids to the herbicide 2,4-dichloro-phenoxy acetic acid, Amino acids, 18, 69-79, 2000. 

Kobek K., Focke M. and LTchtenthaler H.K., 1988. Fatty acid biosynthesis and acetyl-GoA carboxylase as a target of diclofop, fenoxaprop and other aryloxy-phenoxy-propionic acid herbicides. Z. Naturforsch. 43c, 47-54 Kreuzaler F. and Hahlbrock K., 1975. Enzymic Synthesis of an aromatic ring from acetate units. Eur J. Biochem. 205-213. 

There are many studies available concerning the characterization of interface and ionization performance for the thermospray LC-MS analysis of pesticides, herbicides and insecticides, the improvement of detection limits and information content of the mass spectra. Compound classes most frequently studied are the carbamates, organophosphorous pesticides, triazine and phenylurea herbicides, chlorinated phenoxy acetic acids, and sulphonylureas. 

Dichloro phenoxy acetic acid (2,4-D) 0.1 (class), 0.5 (total) Severe eye and dermal irritation, neurotoxicity, and hepatic dysfunction The use as a systemic herbicide for control of broad-leaved weeds, including aquatic weeds 0.1 pg/1 by gas-liquid chromatography with electrolytic conductivity detection... 

Ether Cle va.ge, This is commonly observed as the initial step in the metaboHsm of the phenoxy herbicides 2,4-D (1), (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), and mecoprop (17). A wide variety of bacteria have been isolated which are able to catalyze this reaction (eq. 

Aroclor 1248, Aroclor 1254, and Aroclor 1260. Quantitation is by comparison of chromatograms with standard concentrations of pure compounds treated in an identical manner. The phenoxy acid herbicides (2,4-dichlorophenoxy)acetic acid (2,4-D), sUvex, and (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T) can be deterrnined by electron-capture detection after extraction and conversion to the methyl esters with BF.-methanol. The water sample must be acidified to pH <2 prior to extraction with chloroform. 

Numerous studies on the metabolism of 2,1t-dichlorophenoxy-acetic acid (2,1+-D) and related herbicides in animals have shown that these chemicals are absorbed and distributed rapidly in the body, and are excreted, undegraded, relatively quantitatively in the urine within a week after administration (M Pharmacokinetic studies with 2,1+,5-T in rats and dogs (5.) and in humans (6J supported these findings, and demonstrated that rates of clearance from plasma and elimination in urine depend on dosage level, animal species, and chemical structure of the phenoxy acid being studied ( + ). Corresponding chlorinated phenol metabolites were detected only in ruminants (M or in trace amounts in urine of rats fed very high doses of phenoxy herbicides (7.) ... 

In spite of their record of producing no detectable harm to humans, the phenoxy herbicides 2,4-dichlorophenoxy acetic acid (2,4-D) and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T) have acquired a less than desirable reputation. This reputation has been the result of their association with low levels of impurities. They have commonly been used as a mixture, which contains trace amounts of highly toxic 2,3,7,8-tetrachlorodibenzo-jj-dioxin, a minor product in the manufacturing of 2,4,5-T. In early production of 2,4,5-T a low level of dioxin was retained. Today s manufacturing process produces 2,4,5-T with no more than 0.1 ppm of the 2,3,7,8 tetrachlorodibenzo-]D-dioxin. This association with toxic dioxin and confusion of the public and the media regarding these issues have led to public distrust in the safety of using phenoxys and to the need to establish clearly the extent of human exposure to these compounds as well as the resulting effects of this exposure. 

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