Simón Navarro

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.

Determination of chlorpyrifos, penconazole, fenarimol, vinclozolin and metalaxyl in grapes, must and wine by on-line microextraction and gas chromatography

A rapid gas chromatographic method for determination of residue levels of one insecticide (chlorpyrifos) and four fungicides (penconazole, fenarimol, vinclozolin and metalaxyl) in grapes, must and wine is described. An on-line microextraction method was used. The matrix, once extracted with a mixture of acetone-dichloromethane (1:1, v/v) was filtered and concentrated. Electron-capture detection for chlorpyrifos, penconazole, fenarimol and vinclozolin and mass-selective detection in the selected-ion monitoring mode for metalaxyl were utilised. No clean-up was necessary because there were no interferences in the area of interest of the chromatogram. Linearity of both detectors, in the range 0.02-2 ng/microliter, was checked. In all cases, the correlation coefficient was the same or superior to 0.997. Recoveries from spiked grapes, must and wine ranged from 78% to 101% (fortification level, 0.1-1 mg/kg). Limits of determination were between 0.01 mg/kg for metalaxyl and 0.001 mg/kg for vinclozolin.

Multiresidue method for the rapid determination of organophosphorus insecticides in grapes, must and wine

A rapid multiresidue gas chromatographic method for determining 12 insecticides in grapes, must and wine is described. A simple on-line microextraction method for isolating frequently applied insecticides on vineyard is used. The matrix, once extracted with an acetone-dichloromethane (1:1, v/v) mixture, was filtered and concentrated. Nitrogen-phosphorus detection (NPD) and electron-capture detection (ECD) were used to identify and quantify the insecticides, the findings being confirmed using mass spectrometric detection (MSD). No clean-up was necessary for either NPD or ECD. The regression coefficients relating to linearity were at least 0.99. Recoveries from spiked grape, must and wine samples ranged from 80 to 108% and relative standard deviations were no higher than 16% in the most unfavourable case. Individual detection limits were in the range 0.02-0.1 ng. Limits of quantification varied from 0.01 to 0.05 mg kg(-1), which are below the maximum residue limits set by the legislation of the main wine-producing countries of the European Union. Only in the case of methidathion and quinalphos were the limits of quantification equivalent to the maximum residue limits (0.05 mg kg(-1)) established by Spanish and French legislation, respectively.

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.

Use of farming and agro-industrial wastes as versatile barriers in reducing pesticide leaching through soil columns.

Increased interest has been recently focused on assessing the influence of the addition of organic wastes related to movement of pesticides in soils of low organic matter (OM) content. This study reports the effect of two different amendments, animal manure (composted sheep manure) and agro-industrial waste (spent coffee grounds) on the mobility of 10 pesticides commonly used for pepper protection on a clay-loam soil (OM = 0.22%). The tested compounds were azoxystrobin, cyprodinil, fludioxonil, hexaconazole, kresoxim-methyl, pyrimethanil, tebuconazole, and triadimenol (fungicides), pirimicarb (insecticide), and propyzamide (herbicide). Breakthrough curves were obtained from disturbed soil columns. Cumulative curves obtained from unamended soil show a leaching of all pesticides although in different proportions (12-65% of the total mass of compound applied), showing triadimenol and pirimicarb the higher leachability. Significant correlation (r = 0.93, p<0.01) was found between the observed and bibliographical values of GUS index. The addition of the amendments used drastically reduced the movement of the studied pesticides. Only two pesticides were found in leachates from amended soils, pyrimethanil (<1%) for both, and pirimicarb (44%) in the soil amended with spent coffee grounds. A decrease in pesticide leaching was observed with the increase in dissolved organic matter (DOM) of leachates. The results obtained point to the interest in the use of organic wastes in reducing the pollution of groundwater by pesticide drainage.

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.

Photocatalytic degradation of five sulfonylurea herbicides in aqueous semiconductor suspensions under natural sunlight

In the present study, the photocatalytic degradation of five sulfonylurea herbicides (chlorsulfuron, flazasulfuron, nicosulfuron, sulfosulfuron and triasulfuron) has been investigated in aqueous suspensions of zinc oxide (ZnO), tungsten (VI) oxide (WO(3)), tin (IV) oxide (SnO(2)) and zinc sulfide (ZnS) at pilot plant scale under natural sunlight. Photocatalytic experiments, especially those involving ZnO photocatalysis, showed that the addition of semiconductors in tandem with the oxidant (Na(2)S(2)O(8)) strongly enhances the degradation rate of the herbicides in comparisons carried out with photolytic tests. The degradation of the herbicides follows a first order kinetics according to the Langmuir-Hinshelwood model. In our conditions, the amount of time required for 50% of the initial pesticide concentration to dissipate (t(½)) ranged from 8 to 27 min (t(30W)=0.3-1.2 min) for sulfosulfuron and chlorsulfuron, respectively in the ZnO/Na(2)S(2)O(8) system. None of the studied herbicides was found after 120 min of illumination (except chlorsulfuron, 0.2 μg L(-1)).

Trace analysis of sulfonylurea herbicides in water samples by solid-phase extraction and liquid chromatography-tandem mass spectrometry.

A sensitive method for the simultaneous determination of 30 sulfonylurea herbicides in tap and leaching waters has been developed. Liquid chromatography tandem-mass spectrometry (LC-MS(2)) in electrospray ionization positive mode was used for the separation, identification and quantification of these compounds. The procedure involves a preconcentration step based on solid-phase extraction with a silica-based bonded C(18) cartridge (Sep-Pak Plus) and a N-vinyl-pyrrolidone polymer cartridge (Oasis HLB). The best results were obtained with Oasis HLB using methanol as elution solvent. Average recoveries of 30 analytes from water samples were in the range of 79-115% with a relative standard deviation of <6.1%. The limits of quantification (LOQs) obtained in tap and leaching water samples were in the range of 0.1-5.9 and 0.4-5.8 ng L(-1), respectively. The proposed method was used to determine sulfonylurea herbicide levels in leaching water samples taken from three lysimeters located in an experimental greenhouse.