Photochemistry of imidacloprid in model systems

The photochemical behavior of the neonicotinoid insecticide imidacloprid was studied with regard to different chemical environments. Different model solvents simulated the structure moieties mainly occurring in waxes and cutin of the plant cuticle. Cyclohexane and cyclohexene substituted saturated and unsaturated hydrocarbon chains, whereas ethanol and 2-propanol were models for primary and secondary alcohol groups of cuticular components. After 5 h of irradiation, imidacloprid was completely degraded in all solvents. With 88-96 mol% 1-[(6-chloropyridin-3-yl)methyl]imidazolidin-2-imine was formed as the main product, whereas 1-[(6-chloropyridin-3-yl)methyl]imidazolidin-2-one was identified as minor product in the range 4-6 mol%. By contrast, besides the photoproducts formed in organic solvents, irradiation of the solid imidacloprid on a glass surface delivered a complex variety of unidentified photoproducts. The nucleophilic addition reaction of the main photoproduct, 1-[(6-chloropyridin-3-yl)methyl]imidazolidin-2-imine, with both cyclohexene oxide and methyl 9,10-epoxystearate as model compounds indicates that epoxidized cutin acids are possible reaction partners for the formation of plant cuticle bound residues of imidacloprid, which could explain the reported findings of nonextractable residues of imidacloprid in plants.     

Structural elucidation of phototransformation products of azimsulfuron in water

The photodegradation of the sulfonylurea herbicide azimsulfuron, N-[[(4,6-dimethoxypyrimidin-2-yl)amino]carbonyl]-1-methyl-4-(2-methyl-2H-tetrazole-5-yl)-1H-pyrazole-5-sulfonamide (AZS), was studied in water at different wavelengths and in the presence of photocatalysts. AZS was rapidly degraded by UV light, affording three photoproducts. The main product, accounting for about 70% of photodegraded herbicide, was identified as 6-amino-5-[(4,6-dimethoxypyrimidin-2-yl)methylamino]-1,5,6,8-tetrahydro-7-oxa-8lambda(6)-tia-1,2,5,6-tetraza-azulen-4-one (ADTA) by single-crystal X-ray diffraction. With simulated sunlight irradiation, the reaction was slower and 2-amino-4,6-dimethoxypyrimidine (DPA) and 1-methyl-4-(2-methyl-2H-tetrazole-5-yl)-1H-pyrazole-5-sulfonamide (MPS), arising from a photohydrolytic cleavage of the sulfonylurea bridge, were the only byproducts observed. The reactions followed first-order kinetics. The addition of dissolved organic matter (DOM) did not modify significantly the AZS photodegradation rate. The presence of Fe2O3 accelerated more than twice the reaction rate affording two major products, DPA and MPS, together with minor amounts of N-[[(5-hydroxy-4,6-dimethoxypyrimidin-2-yl)amino]carbonyl]-1-methyl-4-(2-methyl-2H-tetrazole-5-yl)-1H-pyrazole-5-sulfonamide (AZS-OH). The greatest degradation rate was detected in the presence of TiO2. Only the photohydroxylation product AZS-OH was observed, which was transformed rapidly into oxalic acid.     

Characterization of key chromophores formed by nonenzymatic browning of hexoses and L-alanine by using the color activity concept

Thermal treatment of an aqueous solution of D-glucose and L-alanine in the presence of the carbohydrate degradation product furan-2-aldehyde resulted in the formation of a variety of colored compounds, among which (Z)-2-[(2-furyl)methylidene]-5, 6-di(2-furyl)-6H-pyran-3-one (I), [E]- and [Z]-1, 2-bis(2-furyl)-1-pentene-3,4-dione (IIa/IIb), 4, 5-bis(2-furyl)-2-methyl-3H-furan-2-one (III), and (S,S)- and (S, R)-2-[4, 5-bis(2-furyl)-2-hydroxy-2-methyl-3(2H)-pyrrol-1-yl]propionic acid (IVa/IVb) as well as 2-[(2-furyl)methylidene]-4-hydroxy-5-[(E)-(2-furyl)methylidene]methyl -2H-furan-3-one (V) were successfully identified as the most intense by application of the color dilution analysis. To measure the contribution of these colorants to the overall color of the browned Maillard mixture, color activity values were calculated as the ratio of the concentration to the visual detection threshold of each colorant. By application of this color activity concept, 16.0% of the overall color of the Maillard mixture accounted for these five types of colorants, thus confirming them as key chromophores. On the basis of synthetic model experiments, the formation pathways leading to the chromophores IIa/IIb, III, and IVa/IVb were proposed.     

Glycosidic conjugates of C13 norisoprenoids, monoterpenoids, and cucurbates in Boronia megastigma (Nees)

Analysis of a methanolic extract of marc from Boronia megastigma (Nees) using LC-MS (APCI, nominal mass) provided strong evidence for the presence of both glycosides and malonyl glycosides of methyl cucurbates, C13 norisoprenoids including megastigmanes, and monoterpene alcohols. Subsequent fractionation of an extract from the marc using XAD-2 and LH 20 chromatography followed by LC-UV/MS-SPE-NMR and accurate mass LC-MS resulted in the isolation and identification of (1R,4R,5R)-3,3,5-trimethyl-4-[(1E)-3-oxobut-1-en-1-yl]cyclohexyl β-D-glucopyranoside (3-hydroxy-5,6-dihydro-β-ionone-β-D-glucopyranoside); 3,7-dimethylocta-1,5-diene-3,7-diol-3-O-β-D-glucopyranoside; and a methyl {(1R)-3-(β-D-glucopyranosyloxy)-2-[(2Z)-pent-2-en-1-yl]cyclopentyl}acetate stereoisomer (a methyl cucurbate-β-D-glucopyranoside); and provided evidence for 3,7-dimethylocta-1,5-diene-3,7-diol-3-O-(6'-O-malonyl)-β-D-glucopyranoside in boronia flowers.     

Abscisic acid related compounds and lignans in prunes (Prunus domestica L.) and their oxygen radical absorbance capacity (ORAC)

Four new abscisic acid related compounds (1-4), together with (+)-abscisic acid (5), (+)-beta-D-glucopyranosyl abscisate (6), (6S,9R)-roseoside (7), and two lignan glucosides ((+)-pinoresinol mono-beta-D-glucopyranoside (8) and 3-(beta-D-glucopyranosyloxymethyl)-2- (4-hydroxy-3-methoxyphenyl)-5-(3-hydroxypropyl)-7-methoxy-(2R,3S)-dihydrobenzofuran (9)) were isolated from the antioxidative ethanol extract of prunes (Prunus domestica L.). The structures of 1-4 were elucidated on the basis of NMR and MS spectrometric data to be rel-5-(3S,8S-dihydroxy-1R,5S-dimethyl-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (1), rel-5-(3S,8S-dihydroxy-1R,5S-dimethyl-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid 3'-O-beta-d-glucopyranoside (2), rel-5-(1R,5S-dimethyl-3R,4R,8S-trihydroxy-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (3), and rel-5-(1R,5S-dimethyl-3R,4R,8S-trihydroxy-7-oxabicyclo[3,2,1]- oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (4). The antioxidant activities of these isolated compounds were evaluated on the basis of oxygen radical absorbance capacity (ORAC). The ORAC values of abscisic acid related compounds (1-7) were very low. Two lignans (8 and 9) were more effective antioxidants whose ORAC values were 1.09 and 2.33 micromol of Trolox equiv/micromol, respectively.     

Syntheses and biological activities of octahydro-1H-cyclopenta[d]pyrimidine derivatives

Various nitromethylene derivatives were synthesized regioselectively. Compounds 8a-f were obtained by the reaction of 1-((5-chloropyridin-2-yl)methyl)-2-(nitromethylene)-octahydro-1H-cyclopenta[d]-pyrimidine (3) with primary amines and formaldehyde. The synthesized compounds were identified by 1H NMR, HRMS (EI), and IR, and preliminary bioassays indicated that most of them showed moderate insecticidal activities against Aphis craccivora. The relationship between hydrophobicity and biological activity was also discussed.     

Spiro cross-links: representatives of a new class of glycoxidation products

Covalently cross-linked proteins are among the major modifications caused by the advanced Maillard reaction. So far, the chemical nature of these aggregates is largely unknown. Investigations are reported on the isolation of 6-[2-[[(4S)-4-amino-4-carboxybutyl]amino]-6,7-dihydroxy-6,7-dihydroimidazo[4,5-b]azepin-4(5H)-yl]-L-norleucine (10) and N-acetyl-6-[(6R,7R)-2-[[4-(acetylamino)-4-carboxybutyl]amino]-6,7,8a-trihydroxy-6,7,8,8a-tetrahydroimidazo[4,5-b]azepin-4(5H)-yl]-L-norleucine (12) formed by oxidation of the major Maillard cross-link glucosepane 1. Independent synthesis and unequivocal structural characterization are given for 10 and 12. Spiro cross-links, representing a new class of glycoxidation products, were obtained by dehydrogenation of the amino imidazolinimine compounds N6-[2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-5-[(2S,3R)-2,3,4-trihydroxybutyl]-3,5-dihydro-4H-imidazol-4-ylidene]-L-lysinate (DOGDIC 2) and N6-[2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-5-[(2S)-2,3-dihydroxypropyl]-3,5-dihydro-4H-imidazol-4-ylidene]-L-lysinate (DOPDIC 3). These new oxidation products were synthesized, and their unambiguous structural elucidation proved the formation of the spiro imidazolimine structures N6-[(7R,8S)-2-[[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-8-hydroxy-7-(hydroxymethyl)-6-oxa-1,3-diazaspiro[4.4]non-1-en-4-ylidene]-L-lysinate (16), N6-(8R,9S)-2-[(4S)-4-ammonio-5-oxido-5-oxopentyl]amino]-8,9-dihydroxy-6-oxa-1,3-diazaspiro[4.5]dec-1-en-4-ylidene)-L-lysinate (19), and N6-[(8S)-2-[(4-amino-4-carboxybutyl)amino]-8-hydroxy-6-oxa-1,3-diazaspiro[4.4]non-1-en-4-ylidene]-L-lysinate (18), respectively. It was shown that reaction of the imidazolinone 15 led to the formation of spiro imidazolones, structurally analogous to 16 and 19.     

Pyrolysis of [14C]-chlorantraniliprole in tobacco

The pyrolysis of [(14)C]-chlorantraniliprole {3-bromo-1-(3-chloro-2-pyridinal)-N-[4-chloro-2-methyl-6-[(methylamino)carbonyl]phenyl]-1H-pyrazole-5-carboxamide} in tobacco was examined. Typically five commercially available cigarettes were treated separately with either [pyrazole carbonyl-(14)C] or [benzamide carbonyl-(14)C]-chlorantraniliprole at a concentration of 20 ppm (μg chlorantraniliprole equivalent/g cigarette weight; main study) to 40 ppm (for degradate identification only). All treated cigarettes were smoked using an apparatus designed to collect mainstream (MS) and sidestream (SS) smoke through a glass fiber filter and a series of liquid traps. The material balance for recovery of applied radiolabel ranged from 92.4 to 94.9%. Unchanged chlorantraniliprole was the major component found in butt and filter extracts, averaging a total of 17.4-17.9% of the applied radioactivity. A nonpolar degradation product, 2-[3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazol-5-yl]-6-chloro-3,8-dimethyl-4(3H)-quinazolinone, designated 1, represented an average of 10.1-15.9% of the applied radioactivity in the [pyrazole carbonyl-(14)C] or [benzamide carbonyl-(14)C]-chlorantraniliprole cigarettes, respectively. (14)CO(2) was the major degradate, representing an average of 32.9 and 25.1% of the applied radioactivity in pyrazole and benzamide experiments, respectively. In the pyrazole carbonyl label a polar degradate, 5-bromo-N-methyl-1H-pyrazole-3-carboxamide (2) was present in the filter extracts at an average of 9.5% of the applied radioactivity. The most nonpolar degradate, 2,6-dichloro-4-methyl-11H-pyrido[2,1b]quinazolin-11-one (3), was present in [benzamide carbonyl-(14)C]-treated cigarettes only and represented an average of 14.7% of the applied radioactivity.     

Mode of action of novel 2-(benzylamino)-4-methyl-6-(trifluoro- methyl)-1,3,5-triazine herbicides: inhibition of photosynthetic electron transport and binding studies.

Novel 2-(benzylamino)-4-methyl-6-(trifluoromethyl)-1,3,5-triazines have the same 1,3,5-triazine skeleton as atrazine, although some of them, for example, 2-(3-chlorobenzylamino)-4-methyl-6-(trifluoromethyl)-1,3,5-tria zin e [pI(50)(spinach) = 7.21], show a >3 times stronger photosynthetic electron transport inhibitory activity than atrazine [pI(50)(spinach) = 6.72]. The new triazines have only one amino group at the triazine ring, and their molecular shapes are different from atrazine. The replacement of the bound [(14)C]atrazine by 1,3,5-triazines was tested to determine whether the novel 1,3,5-triazine analogues exhibit the same binding pattern at the D1-protein as atrazine. It was found that [(14)C]atrazine bound to the D1-protein was replaced by the triazine tested by a clearly competitive interaction. Obviously, the novel 1,3,5-triazines are attached to the same binding niche as atrazine.     

Parallel synthesis: a new approach for developing analytical internal standards. Application to the analysis of patulin by gas chromatography-mass spectrometry

The polymer-assisted reaction of 4-(hydroxymethyl)furan-2(5H)-one (4HM2F) with 21 carboxylic acids using polystyrene-carbodiimide (PS-carbodiimide) yielded an ester library. Four of the esters, (5-oxo-2,5-dihydrofuran-3-yl)methyl acetate (IS-1), (5-oxo-2,5-dihydrofuran-3-yl)methyl butyrate (IS-2), (5-oxo-2,5-dihydrofuran-3-yl)methyl 2-methylpropanoate (IS-3), and (5-oxo-2,5-dihydrofuran-3-yl)methyl chloroacetate (IS-4), were tested as internal standards for the quantification of patulin in apple juice by gas chromatography-mass spectrometry in the selected ion monitoring mode (GC-MS-SIM). The developed method combines an AOAC official extractive step and a GC-MS-SIM analysis. Using a chromatographic column containing trifluoropropylmethylpolysiloxane as the stationary phase and IS-1 as the internal standard, it was possible to perform an accurate and precise quantification of underivatizated patulin in apple juice at concentrations down to 6 microg/L. A detection limit of 1 microg/L was established.     

Identification of new heterocyclic nitrogen compounds from glucose-lysine and xylose-lysine maillard model systems

Aqueous sugar (glucose or xylose)-lysine model systems were heated at 80 degrees C for 6 h with the pH maintained at a predetermined value (3, 4, or 5). Selected compounds were isolated by combinations of solvent extraction and semipreparative HPLC, prior to identification by NMR and mass spectrometry. Two compounds were identified from the pH 5 glucose system and were identified as epsilon-[2-formyl-5-(hydroxymethyl)pyrrole-1-yl]-L-norleucine (pyrraline) and the new compound, 1-(5-carboxy-5-aminopentyl)-2-formyl-3-(1,2,3-trihydroxypropyl)pyrrole. A third compound was partially characterized. 2-Acetyl-5-hydroxymethyl-5,6-dihydro-4H-pyridinone was identified in the pH 3 xylose system, and the new compound, 8-furan-2-yl-methyl-5-hydroxymethyl-5,6-dihydro-indolizine-1,7-dione, was identified in the pH 4 xylose system. 2-Furfurylidene-4-hydroxy-5-methyl-3(2H)-furanone was identified in both xylose systems. Mechanisms of formation are proposed for the novel compounds.     

Sorption-desorption of imidacloprid and its metabolites in soil and vadose zone materials

Sorption-desorption is one of the most important processes affecting the leaching of pesticides through soil because it controls the amount of pesticide available for transport. Subsurface soil properties can significantly affect pesticide transport and the potential for groundwater contamination. This research characterized the sorption-desorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine) and three of its metabolites, 1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinone (imidacloprid-urea), 1-[(6-chloro-3-pyridinyl)methyl]-4,5-dihydro-1H-imidazol-2-amine (imidacloprid-guanidine), and 1-[(6-chloro-3-pyridinyl)methyl]-1H-imidazol-2-amine (imidacloprid-guanidine-olefin), as a function of changing soil properties with depth in two profiles extending from the surface to a depth of 1.8 or 8 m. Sorption of each compound was highly variable and hysteretic in all cases. Normalizing the sorption coefficients (K(f)) to the organic carbon or the clay content of the soil did not reduce the variability in sorption coefficients for any compound. These results illustrate the importance of evaluation of the sorption data used to predict potential mobility. Understanding the variability of soil properties and processes as a function of depth is necessary for accurate prediction of pesticide dissipation.     

Metabolism and fate of [(14)C]ethametsulfuron-methyl in rutabaga (Brassica napobrassica Mill)

The metabolism and fate of ethametsulfuron-methyl ?methyl 2-[[[[[4-ethoxy-6-(methylamino)-1,3, 5-triazin-2-yl]amino]carbonyl]amino]sulfonyl]benzoate? in rutabaga were investigated. After 72 h, absorption and translocation of [(14)C]ethametsulfuron-methyl in rutabaga did not change for the duration of the study (50 days). Less than 4% of recovered radioactivity was present in the rutabaga root. Ethametsulfuron-methyl was metabolized through a proposed unstable alpha-hydroxy ethoxy intermediate that dissipated 3 days after treatment to two major metabolites, O-desethylethametsulfuron-methyl and N-desmethyl-O-desethylethametsulfuron-methyl, as determined by liquid chromatography-mass spectrometry. It was estimated that at a spray dose of 30 g of active ingredient ha(-)(1) and a harvest weight of 0.5 kg, the edible portion of the rutabaga root would contain no ethametsulfuron-methyl and approximately 1.3 ppb total of both identified metabolites. Residue analysis and toxicological assessment show that ethametsulfuron-methyl and its metabolites should pose little or no risk to consumers of rutabagas.     

Metabolism of furametpyr. 1. Identification of metabolites and in vitro biotransformation in rats and humans

Urinary and fecal metabolites in male rats treated with a (14)C-labeled fungicide, furametpyr [N-(1,3-dihydro-1,1, 3-trimethylisobenzofuran-4-yl)-5-chloro-1, 3-dimethylpyrazole-4-carboxamide, Limber], were purified by a combination of chromatographic techniques, and chemical structures of 14 metabolites were identified by spectroanalyses (NMR and MS). The major biotransformation reactions of furametpyr in rats were found to be (1) N-demethylation, (2) oxidation of the methyl group at C3 of the pyrazole ring, (3) oxidation of the methyl group at C1 of the 1,3-dihydroisobenzofuran ring, (4) hydroxylation at C3 of the 1,3-dihydroisobenzofuran ring, and (5) hydroxylation at C7 of the 1, 3-dihydroisobenzofuran ring. In vitro metabolism by recombinant human cytochrome P450 revealed that a major biotransformation in humans is N-demethylation, catalyzed by CYP1A1, 1A2, 2C19, and 3A4.     

Synthesis and fungicidal evaluation of novel chalcone-based strobilurin analogues

Strobilurin derivatives have become one of the most important classes of agricultural fungicide due to a novel action mode, wide fungicidal spectrum, lower toxicity toward mammalian cells, and environmentally benign characteristics. To discover new strobilurin analogues with high activity against resistant pathogens, a series of new chalcone-based strobilurin derivatives are designed and synthesized by integrating a chalcone scaffold with a strobilurin pharmacophore. The preliminary bioassay showed that some of the chalcone analogues exhibited good in vivo fungicidal activities against Pseudoperoniospora cubensis and Sphaerotheca fuliginea at the dosage of 200 microg mL(-1). Two compounds, (E)-methyl 2-[2-({3-[(E)-3-(2-chlorophenyl)acryloyl]phenoxy}methyl)phenyl]-3-methoxyacrylate (1e) and (E)-methyl 2-[2-({3-[(E)-3-(3-bromophenyl)acryloyl]phenoxy}methyl)phenyl]-3-methoxyacrylate (1l), were found to display higher fungicidal activities against P. cubensis (EC90=118.52 microg mL(-1) for 1e and EC90=113.64 microg mL(-1) for 1l) than Kresoxim-methyl (EC90=154.92 microg mL(-1)) and were identified as the most promising candidates for further study. The present work demonstrated that strobilurin analogues containing chalcone as a side chain could be used as a lead structure for further developing novel fungicides. To our knowledge, this is the first report about the syntheses and fungicidal activities of chalcone-based strobilurin derivatives.     

Synthesis and fungicidal activity against Rhizoctonia solani of 2-alkyl (Alkylthio)-5-pyrazolyl-1,3,4-oxadiazoles (Thiadiazoles)

Some series of 2-alkyl (alkythio)-5-((4-chloro)-3-ethyl-1-methyl-1H-pyrazole-5-yl)-1,3, 4-oxadiazoles (thiadiazoles) were prepared as potential fungicides. Their fungicidal activity was evaluated against rice sheath blight, which is a major disease of rice in China. Structure-activity relationships for the screened compounds were evaluated and discussed. It was found that 5-(4-chloro-3-ethyl-1-methyl-1H-pyrazole-5-yl)-1,3, 4-thiadiazole-2-thione has the higher fungicidal activity.     

Systematic studies on structure and physiological activity of cyclic alpha-keto enamines, a novel class of "cooling" compounds.

3-Methyl- and 5-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one were recently identified as intense cooling compounds in roasted dark malt. To gain more insights into the molecular requirements of these compounds for imparting a cooling sensation, 26 cyclic alpha-keto enamine derivatives were synthesized, and their physiological cooling activities were evaluated. Any modification of the amino moiety, the carbocyclic ring size, or incorporation of additional methyl groups led to a significant increase of the cooling threshold. Insertion of an oxygen atom into the 2-cyclopenten-1-one ring, however, increased the cooling activity, e.g., the cooling threshold of the 5-methyl-4-(1-pyrrolidinyl)-3(2H)-furanone was found to be 16-fold below the threshold concentration determined for the 3-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one. Shifting the oxygen atom from the 4- into the 5-position of the cyclopentenone ring resulted in a even more drastic increase in cooling activity, e.g., the 4-methyl-3-(1-pyrrolidinyl)-2(5H)-furanone exhibited the strongest cooling effect at the low oral threshold concentration of 0.02-0.06 mmol/L, which is 35-fold below the value determined for (-)-menthol. In contrast to the minty smelling (-)-menthol, most of the alpha-keto enamines were found to be virtually odorless but impart a sensation of "cooling" to the oral cavity as well as to the skin, thus illustrating that there is no physiological link between cooling activity and mint-like odors.     

Syntheses and herbicidal activities of novel triazolinone derivatives

Protoporphyrinogen oxidase (Protox, EC 1.3.3.4) has been identified as one of the most important action targets of herbicides. To search for novel Protox inhibitors, a series of title compounds 1, 2, and 3 were designed and synthesized by introducing three types of pharmacophores, cyclic imide, phenylurea, and ( E)-methyl 2-methoxyimino-2- o-tolylacetate, into the scaffold of triazolinone. The bioassay results indicated that the resulting cyclic imide-type triazolinones 1 displayed much better herbicidal activities than phenylurea-type triazolinones 2. Most fortunately, compound 3, methyl 2-[3-methyl-(2-fluoro-4-chloro-5-ethylsulfonamidephenyl)-4,5-dihydro-5-oxo-1 H-1,2,4-triazol-4-yl]methylenephenyl-2-( E)-methoxyiminoacetate, was found to be the most promising candidate due to its comparable herbicidal activity at 75-150 g of active ingredient/ha with the commercial product sulfentrazone. On the basis of test results of herbicidal spectrum and crop selectivity, compound 3 could be developed as a postemergent herbicide used for the control of broadleaf weeds in rice fields.     

Sorption and degradation of azimsulfuron on iron(III)-rich soil colloids

The sorption of N-[[(4,6-dimethoxypyrimidin-2-yl)amino]carbonyl]-1-methyl-4-(2-methyl-2H-tetrazole-5-yl)1H-pyrazole-5-sulfonamide (AZS) on an iron oxide, iron(III)-humate, and an Fe3+-saturated clay was studied using a batch equilibrium method. Generally, 20 mg of each colloid was equilibrated with 20 mL of AZS solution (1.5-12.7 microM). The sorption on iron-montmorillonite and iron oxide was rapid, and the equilibrium was attained within 1.5 and 5 h, respectively. In the case of Fe-saturated humic acid the equilibrium time was 20 h. After equilibration, the phases were centrifuged (19000g, 15 min) and the supernatant was sampled and analyzed by HPLC. The values of Freundlich constants indicate that iron oxide (Kads = 199.5) shows the highest sorptive capacity toward AZS, followed by iron(III)-clay (Kads = 146.6) and iron(III)-humate (Kads = 108.2). With elapsing time, AZS degradation was observed in all colloidal suspensions. Iron-humate (t(1/2) = 136 h) is most effective in promoting AZS degradation, followed by iron oxide (t(1/2) = 204 h) and iron-clay (t(1/2) = 385 h). The metabolites 2-amino-4,6-dimethoxypyrimidine and 1-methyl-4-(2-methyl-2H-tetrazole-5-yl)-1H-pyrazole-5-sulfonamide, arising from a hydrolytic cleavage of the sulfonylurea bridge, were the only byproducts observed. A Fourier transform infrared study suggests that the sorption of AZS on iron-clay involves the protonation of one of the two basic pyrimidine nitrogens induced by the acidic water surrounding the saturating Fe3+ ions. Instead, the formation of a six-membered chelated complex favors the sorption of AZS on iron oxide.