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Multiresidue method for the rapid determination – in grape, must and wine – of fungicides frequently used on vineyards

A rapid multiresidue gas chromatographic method for determining 17 fungicides in grapes, must and wine, widely used on vineyards, is described. A simple on-line microextraction method for isolation of fungicides was used. Nitrogen-phosphorus and electron-capture detection were used for the identification and quantitation of pesticides. For confirmation, mass spectrometic detection was used. Because of the high selectivity of both detection methods, no clean-up was necessary. The regression coefficients relating to linearity were at least 0.994. Recoveries from spiked grapes, must and wine samples ranged from 78 to 107% and relative standard deviations were not higher than 14%. Individual detection limits were in the range 0.02-0.1 ng. Limits of quantification varied from 0.01 to 0.05 mg/kg, smaller in all cases than the maximum residue limits set down by the legislations of Spain, France and Italy, the main wine-producing countries of the European Union. Only for fludioxonil and hexaconazole do the limits of quantification coincide with the maximum residue limits (0.05 mg/kg) established by the Spanish legislation.

Photocatalytic degradation of eight pesticides in leaching water by use of ZnO under natural sunlight.

Photodegradation of eight pesticides in leaching water at pilot plant scale using the tandem ZnO/Na(2)S(2)O(8) as photosensitizer/oxidant and compound parabolic collectors under natural sunlight is reported. The pesticides, habitually used on pepper culture and belonging to different chemical groups were azoxyxtrobin, kresoxim-methyl, hexaconazole, tebuconazole, triadimenol, and pyrimethanil (fungicides), primicarb (insecticide), and propyzamide (herbicide). As expected, the influence of the semiconductor used at 150 mg L(-1) on the degradation of pesticides was very significant in all cases. Photocatalytic experiments show that the addition of photosensitizer strongly improves the elimination of pesticides in comparison with photolytic tests; significantly increasing the reaction rates. The use of Na(2)S(2)O(8) implies a significant reduction in treatment time showing a quicker reaction time than ZnO alone. On the contrary, the addition of H(2)O(2) into illuminated ZnO suspensions does not improve the rate of photooxidation. The disappearance of the pesticides followed first-order kinetics according to Langmuir-Hinshelwood model and complete degradation occurs from 60 to 120 min. The disappearance time (DT(75)), referred to the normalized illumination time (t(30 W)) was lower than 3 min in all cases.

Evolution of residual levels of six pesticides during elaboration of red wines. Effect of wine-making procedures in their dissappearance.

The effect of wine-making procedures on the concentrations of six pesticides (chlorpyrifos, penconazole, fenarimol, vinclozolin, metalaxyl, and mancozeb) in red wines has been studied. During maceration stage (4 days), the percentage remaining of chlorpyrifos, penconazole, and metalaxyl was approximately 90%, whereas that of fenarimol, vinclozolin, and mancozeb is somewhat smaller (74-67%). The residual levels found in pressed must were </=20%, except for metalaxyl (69%). From the whole concentration of chlorpyrifos in must, 85% is eliminated from the racking step; clarification (bentonite plus gelatin) eliminates 43% of the product found in the decanted wine, and with filtration, all of the residue is eliminated. Penconazole and mancozeb are retained on the lees in proportions of 43 and 31%, respectively. The eliminated percentage of vinclozolin after racking is 29%, whereas clarification and filtration reduce its proportion in the wine to 33 and 28%, respectively. Finally, fenarimol and metalaxyl are eliminated in smaller proportion with the realization of these processes.

Assessment of agro-industrial and composted organic wastes for reducing the potential leaching of triazine herbicide residues through the soil

In this study, we examined the effect of four different organic wastes--composted sheep manure (CSM), spent coffee grounds (SCG), composted pine bark (CPB) and coir (CR)--on the sorption, persistence and mobility of eight symmetrical and two asymmetrical-triazine herbicides: atrazine, propazine, simazine, terbuthylazine (chlorotriazines), prometon (methoxytriazine), prometryn, simetryn, terbutryn (methylthiotriazines), metamitron and metribuzin (triazinones). The downward movement of herbicides was monitored using disturbed soil columns packed with a clay loam soil (Hipercalcic calcisol) under laboratory conditions. For unamended and amended soils, the groundwater ubiquity score (GUS) was calculated for each herbicide on the basis of its persistence (as t½) and mobility (as KOC). All herbicides showed medium/high leachability through the unamended soils. The addition of agro-industrial and composted organic wastes at a rate of 10% (w:w) strongly decreased the mobility of herbicides. Sorption coefficients normalized to the total soil organic carbon (KOC) increased in the amended soils. These results suggest that used organic wastes could be used to enhance the retention and reduce the mobility of the studied herbicides in soil.

Photocatalytic transformation of sixteen substituted phenylurea herbicides in aqueous semiconductor suspensions: Intermediates and degradation pathways

The photocatalytic degradation of sixteen substituted phenylurea herbicides (PUHs) in pure water has been studied using zinc oxide (ZnO) and titanium dioxide (TiO(2)) as photocatalyst under artificial light irradiation. Photocatalytic experiments showed that the addition of these chalcogenide oxides in tandem with the oxidant (Na(2)S(2)O(8)) strongly enhances the degradation rate of these compounds in comparison with those carried out with ZnO and TiO(2) alone and photolytic tests. Comparison of catalysts showed that ZnO is the most efficient for the removal of such herbicides in optimal conditions and at constant volumetric rate of photon absorption in the photoreactor. Thus, the complete disappearance of all the studied compounds was achieved after 20 min of illumination in the ZnO/Na(2)S(2)O(8) system. The main photocatalytic intermediates detected during the degradation of PUHs were identified. The probable photodegradation pathways were proposed and discussed. The main steps involved: N-demethylation of the N,N-dimethylurea-substituted compounds followed of N-demethylation and N-demethoxylation of the N-methoxy-N-methyl-substituted ureas and hydroxylation of aromatic rings and their aliphatic side-chains of both, parent compounds and intermediates.

Decline of pesticide residues from barley to malt

The fate of dinitroaniline herbicides (pendimethalin and trifluralin), organophosphous insecticides (fenitrothion and malathion), and pyrimidine (nuarimol) and triazole (myclobutanil and propiconazole) fungicides from barley to malt was determined. Several samples for residue analysis were taken after each stage of malting (steeping, germination and kilning). Pesticide residue analysis was carried out by GC/ITMS in selected ion monitoring mode. Pesticides decline along the process, although in different proportions. The carryover of residues after steeping was 45–85%. A good correlation (r > 0.92) was observed between percentages removed after steeping and the P OW values of pesticides. The amount remaining after malting ranged from 13 to 51% for fenitrothion and nuarimol, respectively. Steeping was the most important stage in the removal of pesticide residues (52%) followed by germination (25%), and kilning (drying and curing, 23%). During malt storage (3 months) the fall in pesticide residues was not significant. Applying the standard first-order kinetics equation (r > 0.95), the half-lives obtained for the pesticides during malt storage varied from 244 to 1533 days for myclobutanil and nuarimol, respectively.

Photocatalytic degradation of substituted phenylurea herbicides in aqueous semiconductor suspensions exposed to solar energy

The photocatalyzed degradation of the biocides chlorotoluron, diuron, fluometuron, isoproturon and linuron (substituted phenylurea herbicides) was investigated in aqueous suspensions of ZnO, TiO2, WO3, SnO2 and ZnS at pilot plant scale under natural sunlight. Comparison of the five catalysts showed that ZnO is the most effective for catalyzing the removal of all the compounds studied. The primary degradation of the herbicides followed a pseudo-first order kinetics. In our conditions, the time required for 90% degradation ranged from 23 to 47min for isoproturon and linuron, respectively, when using the tandem ZnO/Na2S2O8. Eight transformation products were identified by HPLC-MS(2) during the experiments, although at the end of the photoperiod (240min), their concentrations were below detection limits. Based on derivative identification, the proposed metabolic pathways would involve N-demethylation and N-demethoxylation of the N-methoxy-N-methyl substituted ureas and N-demethylation of the N,N-dimethylurea-substituted compounds.

Decay of Dinitroaniline Herbicides and Organophosphorus Insecticides during Brewing of Lager Beer

This article examines the fate of four pesticides that can be present during the brewing of lager beer. For this purpose, malted barley was spiked at 2 mg/kg with pendimethalin and trifluralin (dinitroaniline herbicides) and fenitrothion and malathion (organophosphorus insecticides). Analyses of pesticide residues were carried out by a gas chromatograph with an electron capture detector, and their identity was confirmed by gas chromatography-mass spectrometry. Cleanup was necessary for the malt and spent grain samples. Beginning with mashing and ending with the final product 4 months later, various samples (spent grain, sweet wort, brewer wort, and beer) were taken to determine the concentration of the targeted residual pesticides during the various beer making phases. In all cases, the residual levels recorded in sweet wort sampled after the mashing phase were below the respective maximum residue limits established by Spanish legislation for barley. Significant proportions of pesticide residues (17 to 40%) were retained on the spent grain. Applying the standard first-order kinetics equation (r > 0.91), the half-lives obtained for the four compounds during the storage of the spent grain (3.5 months) varied from 138 days (fenitrothion) to 192 days (malathion and pendimethalin). Herbicide residues practically disappeared (<0.3%) after wort boiling, whereas the percentages of the remaining insecticides, fenitrothion and malathion, ranged from 3.5 to 4.3%, respectively, at this time. No residues of dinitroaniline compounds were detected in young beer, whereas there was a significant reduction in fenitrothion (58%) and malathion (71%) residues during fermentation. Lagering and filtering processes also reduced the content of the organophosphorus insecticides (33 to 37%). Finally, after the storage period (3 months), the content of fenitrothion was reduced by 75%, with malathion residues being below its detection limit.

Effect of wine-making practices on the concentrations of fenarimol and penconazole in rose wines

The changes in and influence of the anti-powdery-mildew fungicides fenarimol and penconazole were studied in the production and quality of rosé wines made with Monastrell grapes grown in the Jumilla wine-producing region in SE Spain. Fungicide concentrations were estimated by gas-liquid chromatography with electron-capture detection. Fermentation was retarded more by penconazole than by fenarimol; in both cases, the slowdown was directly proportional to fungicide concentration. However, the mature wine contained normal concentrations of residual sugars; other enological parameters (pH, volatile acidity, intensity of color and hue) were not significantly affected. Thirty-four days after the start of the experiment, 67% of fenarimol and 52% of penconazole, with respect to the smaller amount initially added (1 mg/liter), were found in the finished wine. The calculated half-life times were 45 and 59 days for penconazole and fenarimol respectively. Different wine-making techniques (racking, clarification, and filtration) had no decisive influence on the removal of fungicide residues from the must, although they eliminated slightly more penconazole than fenarimol.

Gradual Fall of s-Triazine Herbicides in Drinking and Wastewater Samples as Influenced by Light and Temperature

The effect of light and temperature on the dissipation of four s-triazine herbicides (terbuthylazine, simazine, atrazine and prometryn) was studied in drinking and wastewaters during long-term laboratory incubation (4 months), and by comparing the results with those obtained in purified water (Milli-Q). Residues were analyzed by GC-NPD and confirmed by GC-MSD. A micro on-line method for isolating the herbicide residues was used. The results showed that temperature and light had a certain influence on the behaviour of the s-triazine herbicides. In drinking water, prometryn dissipated more rapidly than the other compounds under all laboratory conditions (t1/2= 75–128 days), while atrazine showed the highest degree of persistence (t1/2= 132–227 days). In general, atrazine was the least (t1/2= 90–142 days) and simazine the most (t1/2= 118–278 days) persistent compound in Milli-Q and wastewater. Only in the case of atrazine in drinking water was the remaining percentage at the end of the experiment higher than 50% (53–69%). Dissolved organic substances in wastewater (DOC, 53.3 mg l−1) appear to be particularly important in the photosensitization process. The time required to reach the maximum admissible concentration (MAC) according to European legislation (0.1 μg l−1) ranged from 3 to 10 years for prometryn and atrazine, respectively, in drinking water depending on the used conditions.