Phenoxy Carboxylic Acid Research Articles

Behavior of selected priority organic pollutants in horizontal subsurface flow constructed wetlands: A preliminary screening

A discrete injection experiment was carried out in a constructed wetland to evaluate the behavior of selected priority pollutants. A horizontal subsurface flow pilot plant located in the NE of Spain was selected for this study. A total of eight European Priority Pollutants listed in the Water Framework Directive were considered, including a commonly used herbicide (mecoprop). The pollutants encompassed a variety of chemical classes and physicochemical properties. They included organochlorine, organophosphorus, phenols, chloroacetanilides, triazine, phenoxycarboxylic acid and phenylurea pesticides. A time series of composite effluent samples and discrete gravel bed samples from the wetland were analyzed. Response curves for all the pollutants injected from effluent concentrations were obtained and compared with the tracer (clofibric acid). On the basis of an analysis of the samples taken 21 days after the injection, priority pollutants were classified into four groups according to their removal efficiency. These groups were (i) the highly efficiently removed (>90%), namely lindane, pentachlorophenol, endosulfan and pentachlorobenzene; (ii) the efficiently removed (80–90%), namely alachlor and chlorpyriphos; (iii) poorly removed (20%), namely mecoprop and simazine; and (iv) recalcitrant to elimination, namely clofibric acid and diuron. Taking into account the poor accumulation of the injected contaminants in the gravel bed (0–20%), biodegradation and plant uptake are postulated as the most likely elimination pathways for the pollutants.

Determination of herbicides of the chlorophenoxycarboxylic acid type in natural and drinking water by capillary zone electrophoresis

The method of capillary electrophoresis was applied to separate and quantitatively determine herbicides belonging to the class of chlorophenoxycarboxylic acids: 2,4-dichlorophenoxyoleic, 2,4-dichlorophenoxypropionic, 2,4,5-trichlorophenoxyacetic, 2,4-dichlorophenoxyacetic, and phenoxyacetic, and the final product of their decomposition in an aqueous medium of 2,4-dichlorophenol. The influence exerted by α- and β- cyclodextrin on the selectivity of the separation system under study was analyzed. The hindering effect of humic acids on the separation and determination of phenoxycarboxylic acids by capillary electrophoresis was assessed.

Mode of action of auxin herbicides: a new ending to a long, drawn out story

In the more than fifty years since their initial discovery, synthetic compounds possessing phytohormonal auxin activity have been among the most successful herbicides and bioregulators used in agriculture 1. Cobb A. Cobb A. Auxin-type herbicides. In Herbicides and Plant Physiology. Chapman & Hall, 1992: 82-106 Google Scholar , 2. Devine M. Physiology of Herbicide Action. Prentice Hall, 1993 Google Scholar , 3. Sterling T.M. Hall J.C. Mechanism of action of natural auxins and the auxinic herbicides. in: Roe R.M. Herbicide Activity: Toxicology, Biochemistry and Molecular Biology. IOS Press, Amsterdam1997: 111-141 Google Scholar , 4. Grossmann K. Quinclorac belongs to a new class of highly selective auxin herbicides. Weed Sci. 1998; 46: 707-716 Google Scholar . With their ability to control dicot weeds in cereal crops, these so-called synthetic auxins were among the first selective organic herbicides to be developed for agricultural use. They have revolutionized modern crop production. Various chemical classes of auxin bioregulators and herbicides with different weed spectra and types of selectivity have been synthesized and commercially introduced over the years. They include indole acids [derivatives of indole-3-acetic acid (IAA)], naphthalene acids, phenoxycarboxylic acids, benzoic acids, pyridine carboxylic acids and a relatively new category, the quinolinecarboxylic acid-type, exemplified by quinmerac and quinclorac (Fig. 1). Unlike other auxin herbicides, quinclorac has herbicidal activity on grass weeds 4. Grossmann K. Quinclorac belongs to a new class of highly selective auxin herbicides. Weed Sci. 1998; 46: 707-716 Google Scholar . In spite of extensive research following F.A. Gilbert's statement that auxin herbicides cause susceptible plants ‘to grow themselves to death’ 5. Gilbert F.A. The status of plant-growth substances and herbicides. Chem. Rev. 1946; 39: 199-218 Crossref PubMed Scopus (9) Google Scholar , until recently auxin herbicides had resisted all efforts to elucidate the details of their molecular interactions and the biochemical basis of their phytotoxicity.

Negative cross-resistance in triazine-resistant biotypes ofEchinochloa crus-galliandConyza canadensis

Abstract Whole-plant, negative cross-resistance was studied in Conyza canadensis and Echinochloa crus-galli, important global weeds. Negative cross-resistance can be a most useful preemptive, cost-effective tool for delaying the evolution of resistance, as well as for resistance management, after resistant populations evolve. Seeds of triazine-resistant and -susceptible biotypes were collected in or near orchards that had been continuously treated with atrazine for more than 10 yr. Plants grown from the seeds were treated, in a greenhouse, with herbicides from the following chemical families: triazine, benzothiadiazole, phenyl-pyridazine, arylophenoxy-propionate, cyclohexanedione, phenoxycarboxylic acid, pyridine carboxylic acid, phosphinic acid, glycine phosphate, chloroacetamide, sulfonylurea, and bipyridylium. Eleven of the 18 herbicides tested exerted significant negative cross-resistance against atrazine-resistant weeds, ranging from 0.03 to 0.67 of the concentration required to affect the triazine-s...

Development of an ELISA for 2,4-D: characterization of two polyclonal antisera

A direct competitive ELISA for the detection of the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid) has been developed. The optimization, evaluation and characterization of the ELISA, with two different antisera, has been carried out. The detection limit of 2,4-D with antiserum 7/89 was 20 ng/l and a center point value of 0.6 μg/l 2,4-D. Antiserum 16/88 showed a detection limit of 0.3 μg/l with a center point value of 4 μg/l. The cross reactivity both at the center point and at the detection limit for five structural related phenoxycarboxylic acid herbicides has been determined. The influence of increasing concentrations of humic acid, solvents and surfactants on the ELISA has been investigated, leading to a deterioration of detection limits and center points.

Analysis of Phenoxycarboxylic Acids and Other Acidic Compounds in Tap, Ground, Surface and Sewage Water at the Low ng/1 Level

Abstract Solid-phase extraction with RP-C18 phase has been successfully applied for the determination of more than 30 acidic herbicides and related compounds from environmental water samples. Detection of these contaminants was performed after pentafluorobenzylation at the low ng per liter level using gas chromatography/mass spectrometry. With multiple-component SIM programming simultaneous detection of all compounds in one single gas chromatographic run was possible. Increased reliability of acidic herbicide analysis from water samples with high matrix content was achieved by using a surrogate as well as an internal standard. 2-(4-chlorophenoxy) butyric acid, being a structural isomer of clofibric acid and mecoprop, was chosen as surrogate standard because cloflbric acid was found to be a widespread contaminant in environmental water samples from the Berlin area. Mecoprop, dichlorprop and 1-naphthylacetic acid were also found in field studies of some of these samples. A few examples of positive findings in tap, ground, surface and sewage water samples are presented.

Chromatographic separation of the enantiomers of marine pollutants. Part 5: Enantioselective degradation of phenoxycarboxylic acid herbicides by marine microorganisms

The degradation of the racemate of the herbicide 2-(2,4-dichlorophenoxy) propionic acid [Dichlorprop; DCPP] by a marine microbial community was investigated by High-performance liquid chromatography [HPLC] using α 1-AGP as chiral stationary phase. The microorganisms degraded exclusively the R-enantiomer, while the S-enantiomer remained unaffected. 2,4-Dichlorophenol was identified as the first degradation product of the R-enantiomer, which implies an increase in toxicity by about an order of magnitude according to the MICROTOX-test.

Enantiomeric effects on excitation-contraction coupling in frog skeletal muscle by a chiral phenoxy carboxylic acid

Aromatic monocarboxylic acids are known to significantly potentiate the mechanical response of skeletal muscle fibers. In this study we investigated the effects of enantiomers of 2-(4-chlorophenoxy)propionic acid, chemically one of the simplest aromatic monocarboxylic acids with chiral properties, on mechanical threshold and charge movement in frog skeletal muscle. The R(+), but not the S(-), enantiomer lowered rheobase mechanical threshold and shifted charge movement to more negative potentials. The R(+) enantiomer also significantly slowed charge movement kinetics, with pronounced delays of the OFF charge transitions. These effects required high temperature for their production. The stereospecific actions of the R(+) enantiomer are interpreted in terms of a specific interaction of this compound at an anion-sensitive site involved in excitation-contraction coupling, most likely on the dihydropryidine-sensitive voltage sensor in the T-system.

Radioimmunoassay for 2,4-dichlorophenoxyacetic acid.

Antisera to 2,4-dichlorophenoxyacetic acid (2,4-D), a widely used herbicide, have been obtained from rabbits following immunization with various 2,4-D-protein conjugates. Employing [125I] 2,4-D-tyramine as the radioligand for the antisera, very poor assay sensitivity was achieved because of a much higher affinity of the antibodies to the tracer. When using [6-3H] 2,4-D(specific radioactivity 465 GBq/mmol) a sensitive and specific radioimmunoassay (RIA) for 2,4-D could be developed, which allows determination directly in water, plasma and urine samples. Levels as low as approximately 100 pg (450 femtomoles) of 2,4-D can be detected. The antiserum is fairly specific for 2,4-D. Other related phenoxycarboxylic acids and dichlorophenol showed a cross-reactivity smaller than 10%. After a single administration of 2,4-D (0.91 mg/100 g body weight, orally) to rats, plasma and urine levels were determined at different times. Results correspond to those found in the literature, thus indicating the utility of the RIA. Further applications and limitations are discussed.

Identifizierung ausgewählter Pestizide im Wasser mit Hilfe eines screening‐Systems auf Grundlage der Dünnschichtchromatographie

AbstractAfter their extraction from water, 16 water pollutants of the families of triazines, urea herbicides, phenoxycarboxylic acids and organochlorine and organophosphorus insecticides are separated and identified by thin‐layer chromatography. The method is suitable for routine analyses and was tested on model waters, inclusive of water from the Elbe river. The rate of redetection is up to 80%, the detection limit is at 0.5… 2 μg of the individual pollutants.

Determination of phenoxy carboxylic acid pesticides by gas and liquid chromatography

Various methods for the chromatographic determination of carboxylic acids are described and compared. These include gas chromatography (GC) after pentafluorobenzylation, high-performance liquid chromatography (HPLC) of the underivatized compounds in the ion-suppression and in the ion-pair mode and HPLC of naphthacyl and methylmethoxycoumarin esters. The GC method has an excellent sensitivity and all the derivatives can be separated on one of the two columns used. A big disadvantage is the fact that many side-products are formed during the derivatization. The underivatized acids can all be separated by HPLC and this method is very easy to perform, but the sensitivity is poor and the wavelength of detection is not specific. With the naphthacyl esters the sensitivity is increased by a factor of 10-20 and with the methylmethoxycoumarin esters the sensitivity is increased by a factor of 5-10. The latter reagent has the advantages that it forms the lowest number of side-products and permits a rather specific detection.

Hysteresis of macroporous organic sorbents

The effect was studied of the properties of the macroporous organic sorbent Separon SE 50/50 on the sorption recovery of s-triazines and phenoxycarboxylic acids from waters. Gas chromatography was employed for the analysis. A property of the sorbent referred to as hysteresis is described and possible errors of determination emerging from it are discussed. A procedure (multiple phase change) is suggested for eliminating the hysteresis effect on recovery.

Méthode d'analyse par chromatographie liquide haute performance des formultions à base de mélanges d'acides phénoxycarboxyliques, de dicamba, d'ioxynil et de bromoxynil

High-performance liquid chromatography analysis of formulations of phenoxycarboxylic acids, dicamba, ioxynil and bromoxynil mixtures Eighteen mixed formulations of phenoxycarboxylic acids and other herbicides such as dicamba, ioxynil and bromoxynil have been analyzed by high-performance liquid chromatography using a r-μm Nucleosil 50 column. The concentration of acetic acid in the eluent hexane-acetic acid depends on the formulation to be analyzed and on the analysis time. The formulations are extracted with a chloroform-diethyl ether mixture, and 20 μ1 of the extract are injected onto the coloumn. The compounds are detected at 285 nm. The method is simple, rapid and the formulations are specificially analyzed without derivatization.

Stereoselectivity and affinity in molecular pharmacology. III. Structural aspects in the mode of action of natural and synthetic auxins

Analysis of available potency estimates for 35 pairs of enantiomeric arylcarboxylic acids with auxin activity (flax-root-growth inhibition test) revealed extensive correlations between the activity of the more potent and less potent isomers, as well as between the log of the ratio of potencies and the log potency of the more active isomer when structurally similar analogs are compared. 5 structural subgroups were discernible (n, eudismic-affinity quotient (EAQ), r 2); (1) arylpropionic acids (6, −0.36, 0.66); (2) 2-naphthoxy-carboxylic acids (6, +1.07, 0.99); (3) 1-naphthoxycarboxylic acids (3, +1.56, 0.96); (4) ortho-substituted phenoxycarboxylic acids (10, +0.97, 0.96) and (5) ortho-unsubstituted phenoxycarboxylic acids (10, +0.56, 0.70). For achiral lower homologs such as auxin itself 3-indolyl-acetic acid (IAA), phenoxyacetic acid and 1-naphthoxyacetic acid, extrapolated potencies were found to agree well with experimental values. On the basis of these observations an auxin receptor is postulated and binding arrangements are described which explain most of the experimental data available. A 3-point attachment when allowed is the only binding mode compatible with the reported data.

Chemistry of Some Amino Acid Derivatives of Phenoxyalkylbutyric Acids

HIS paper reports on the synthesis and properties of 38 new herbiT cides, amino acid derivatives of 4-(2,4-dichlorophenoxy)and 4-(2-methyl-4-chlorophenoxy)butyric acids. The biological evaluation of the compounds as selective herbicides is being conducted by other investigators and will be published later. In the past 18 years major advances have been made in the regulation of plant growth by use of synthetic organic compounds. Many of these new synthetics have reached commercial production and are widely utilized as herbicides. The most prominent among these have been the variously substituted phenoxyalkylcarboxylic acids. The literature abounds with reports on their structural configuration in relation to mode of action, growth-regulating properties and selective herbicidal properties. These researchers were stimulated by the early work on 2,4-dichlorophenoxyacetic acid and other related compounds triggered by such preparative contributions as Pokorny's (7) in 1941. Shaw and Gentner (9) in their paper on the selective herbicidal properties of substituted phenoxyalkylcarboxylic acids have briefly reviewed the literature on some of the most significant contributions concerning the biological activity of these acids. Preliminary investigations 2,3 have shown that the chemical attachment of an amino acid through amide linkage to variously substituted phenoxycarboxylic acids affects the selective herbicidal properties of the latter. The effect seems to depend upon the type of amino acid and its optical configuration. The optimum effect observed so far has been with an amino acid phenoxy-cx-propionic acid series.4 Preliminary screening tests5 (3, 4, 5) designed to measure growth-regulating activity of these compounds have been in close agreement with herbicidal evaluation data.4 Activity tests have shown, for instance, a wide difference in the behavior pattern of compounds made from D-, Land DLoptical forms of amino acids. This difference was greater in the cc-propionic acid4 (3) than in the

Plant Growth Regulators, Synthesis and Preliminary Evaluations of Amide, Lactic Acid, and Terpenoid Derivatives of Substituted Phenoxycarboxylic Acids

Plant Growth Regulators, Synthesis and Preliminary Evaluations of Amide, Lactic Acid, and Terpenoid Derivatives of Substituted Phenoxycarboxylic Acids