Vincenzo L. Garau

Phenolic compounds in virgin olive oils I. Low-wavelength quantitative determination of complex phenols by high-performance liquid chromatography under isocratic elution

Abstract An HPLC method that allows the determination of complex phenolic compounds at low λ (225 nm) after solid-phase extraction from virgin olive oils is reported. The separation was achieved on ODS-2, ODS-1 and C8 columns in eluting mixtures 10−3 M H2SO4CH3CN employed with different ratios. The method was employed for the quantitative determination of phenolic compounds in oils. It allows the presence of some new unknown compounds to be shown. The preliminary spectroscopic data of these compounds, probably phenolic, are reported. The reactivity with protic solvents of the deacetoxy oleuropeine aglycon is discussed.

Residues of azoxystrobin, fenhexamid and pyrimethanil in strawberry following field treatments and the effect of domestic washing.

Residues of the pesticides azoxystrobin, fenhexamid and pyrimethanil were determined in strawberry after field treatment. The effect of ‘home’ washing with tap water and a commercially available vegetable detergent on residue levels was also studied. After treatment, azoxystrobin and pyrimethanil residues on strawberry were on average 0.55 and 2.98 mg kg−1, respectively, values below the maximum residue level (MRL) fixed by the European Union (2.0 and 5 mg kg−1, respectively), while fenhexamid residues were on average 2.99 mg kg−1, which is very close to the MRL of 3.0 mg kg−1, but some samples were over the MRL. Thereafter, all residues declined, with a half-life of about 8 days (azoxystrobin and fenhexamid) and 4.8 days (pyrimethanil). Washing the fruit with tap water reduced the residues of azoxystrobin and fenhexamid but did not affect pyrimethanil residues. Finally, when fruits were washed with a commercial detergent, greater amounts were removed (about 45% of azoxystrobin and pyrimethanil and 60% of fenhexamid).

Persistence and Effectiveness of Pyrethroids in Plastic Strips Against Varroa jacobsoni (Acari: Varroidae) and Mite Resistance in a Mediterranean Area

Abstract An apiary trial was conducted in 1997 in Sardinia, Italy, to verify the effectiveness of fluvalinate in polyvinyl chloride strips and flumethrin in polyethylene strips against Varroa jacobsoni Oudemans. Two indices to evaluate the efficacy of the treatments were adopted: percentage change in mite infestation of worker-sealed brood cells considering only treated hives and percentage change in mite mortality, and the natural variation in mite populations recorded in control hives during the trial. All acaricide treatments reduced the level of mite infestation of both sealed brood and adult bees. However, their effectiveness was slightly reduced in comparison to previous studies because of mite resistance phenomena. Portions of polyethylene strips of flumethrin from treated hives were sampled weekly to determine acaricide persistence using gas chromatography. After 4 wk, a slight reduction (≈9%) of the active ingredient content was observed. A laboratory bioassay also was performed to establish the resistance of adult female mites to fluvalinate. Mites were sampled from the experimental apiary and from various Sardinian apiaries which had primarily been subjected to fluvalinate applications in plastic strips or wood inserts for years. Mite resistance varied from 0 to 96%, depending on the acaricide management adopted. The lowest resistance level occurred in an apiary where pyrethroids had never been used, whereas the highest level occurred in an apiary with intensive use of fluvalinate in wood inserts.

Fenhexamid residues in grapes and wine

The behaviour of the fungicide, fenhexamid, on grapes, and during wine-making, as well as its effect on the microflora of alcoholic and malolactic fermentation has been studied. After treatment, the residue on grapes decreased rapidly to one-third of the initial level after the first week, while it remained constant during the following two weeks. At harvest, in the wine obtained by vinification without skins, the fungicide residue decreased on average by 49%, while in the wine obtained by vinification with skins, the decrease was on average 62%. The presence of this fungicide on grapes and in the wine did not affect alcoholic and malolactic fermentation, nor did fermentation cause any degradation of the fungicide. A simple and rapid gas chromatograhic method (GC-NPD) for the determination of fenhexamid residues in grapes, must and wine is described.

Residue-free Wines: Fate of Some Quinone outside Inhibitor (QoI) Fungicides in the Winemaking Process

The fate of three fungicide residues (fenamidone, pyraclostrobin, and trifloxystrobin) from vine to wine was studied to evaluate the decay ratio and the influence of the technological process. The aim of this work was to identify pesticides that can degrade rapidly or be eliminated together with byproduct (lees and cake) of the winemaking process to obtain wine free of residues. The disappearance rate on grapes was calculated as pseudo-first-order kinetics, and the half-life (t(1/2)) was in the range from 5.4 +/- 1.9 to 12.2 +/- 1.2 days. The mechanism of dissipation of the three quinone outside inhibitor (QoI) fungicides was studied using different model systems. It was observed that the main mechanism responsible for disappearance was photodegradation. For active ingredients (ai) the half-lives of fenamidone, pyraclostrobin, and trifloxystrobin were 10.2 +/- 0.8, 20.1 +/- 0.1, and 8.6 +/- 1.0 h, respectively, whereas for formulation higher half-lives were observed when epicuticular waxes were present (from 13.8 +/- 0.2 to 26.6 +/- 0.1 h). After winemaking, fenamidone, pyraclostrobin, and trifloxystrobin residues were not detected in the wine, but they were present in the cake and lees. This was due to the adsorption of pesticide residues to the solid parts, which are always eliminated at the end of the alcoholic fermentation. The data obtained in these experiments suggest that these three active ingredients could be used in a planning process to obtain residue-free wines.

THE EFFECT OF SIMULATED RAIN ON FOLPET AND MANCOZEB RESIDUES ON GRAPES AND ON VINE LEAVES

Artificial rainfalls were used to determine the effect of the amount of the rainfall and the time interval between pesticide application and rainfall event, on folpet and mancozeb residues on grapes and vine leaves. Forty-five mm of rain were administered to the vineyard in different amounts (45; 30+15; + 15 15+15 mm). Folpet showed good rainfastness on the grapes and on the leaves. A modest decrease was observed only in the experiments that had received 45 mm of rain at one go. Mancozeb showed a lower rainfastness, since a portion of the deposit was easily washed off also by a modest rainfall. The percentage of this portion was higher in the grapes (38%) than in the leaves (20%). The data obtained in these experiments show that, in the case of folpet, it is not necessary to repeat the treatment when it rains the day after, while it is recommendable to repeat it in the case of mancozeb.

Residues of the fungicide famoxadone in grapes and its fate during wine production

Abstract Famoxadone is a recently applied fungicide to vines that belongs to the oxazolidinedione family. The fate of famoxadone was studied by considering the decay ratio of this fungicide during the maturation of grapes and wine production. The main factors affecting the presence of fungicide residues such as fruit growth, photodegradation, evaporation, thermodegradation and co-distillation were studied with model systems. An experimental field was treated with a commercial product containing famoxadone at the recommended dose. After this application, residues of famoxadone were found in grapes at 0.27 ± 0.06 mg kg–1. In this field experiment, the half-life (t 1/2;) of famoxadone, which is described by pseudo-first-order kinetics (R 2 = 0.74), was 18 ± 6 days, resulting from the photodegradation. The famoxadone residue levels in grapes were below the established maximum residues level for Europe (2 mg kg–1), whilst levels in wine, carried out with and without maceration, were below the calculated limit of detection of the method.

Nematicidal activity of allylisothiocyanate from horseradish (Armoracia rusticana) roots against Meloidogyne incognita.

In recent years, there has been a great development in the search for new natural pesticides for crop protection aiming a partial or total replacement of currently used chemical nematicides. Glucosinolate breakdown products are volatile and are therefore good candidates for nematodes fumigants. In this article, the methanol-aqueous extract (1:1, w/v) of horseradish (Armoracia rusticana) fresh roots (MAH) was in vitro tested for nematicidal activity against second stage (J2) Meloidogyne incognita. The EC50 of MAH after 3 days of J2 immersion in test solutions was 251 ± 46 mg/L. The chemical composition analysis of the extract carried out by the GC-MS technique showed that allylisothicyanate was the most abundant compound. This pure compound induced J2 paralysis with an EC50 of 52.6 ± 45.6 and 6.6 ± 3.4 mg/L after 1 h and 3 days of incubation. The use of LC-MS/MS showed for the first time that horseradish root is rich in polyphenols. The study of isothiocyanate degradation in soil showed that allylisothiocyanate was the most quickly degradable compound (half-life <10 min), whereas no significant differences in half-life time were noted between degradation in regular and autoclaved soil.

The effect of clarifying substances on organophosphorous insecticide residues in wine

Abstract The influence of six clarifying agents (bentonite, charcoal, potassium caseinate, gelatine, polyvinylpolypyrrolidone and colloidal silicon dioxide) on pesticide residues in wine was studied. Thirteen pesticides belonging to the class of organophosphorous insecticides were studied at two different doses. Almost all clarifying agents showed no or limited ability in reducing pesticide residues. The only exception was charcoal which allowed complete or almost complete elimination of pesticide residues, especially when they were at lower doses. Charcoal activity usually decreased on increasing pesticide water solubility. Therefore, pesticides that are highly soluble in water, such as dichlorvos and dimethoate, showed no sensible decrease.

Interactions during fermentation between pesticides and oenological yeasts producing H2S and SO2

The degradative action of two strains of Saccharomyces cerevisiae, producers of large quantities of H2S and SO2, on eight sulphur-containing insecticides (chlorpyrifos-methyl, dimethoate, fenitrothion, fenthion, malation, methidation, parathion, and quinalphos) was studied. Moreover, the influence of these compounds on the fermentative activity of the yeasts was investigated. The yeasts adsorbed and degraded the studied insecticides to various extents, but their fermentative activity was not affected. A moderate adsorbtion (approximately 10% of the residue) was observed for chlorpyrifos-methyl, fenitrothion, parathion, and quinalphos. When absorbed, the insecticides were also degraded by about 50%. The degraded pesticides belong to the thiophosphates, while the dithiophosphates showed higher stability. The two yeast strains showed analogous degradative actions.