Determination of forchlorfenuron in fruits by solid phase or QuECHERS extraction and LC-UV or LC/MS/MS.

Forchlorfenuron, N-(2-chloro-4-pyridinyl)-N'-phenylurea, is a plant growth regulator used to increase the size of kiwifruit, apples, table grapes, and peaches and to promote increased yields of potatoes, rice, and wheat. This study reports the comparison of the performances of two extraction methods [Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) and SPE] and two analytical methods (LC-UV and a LC/MS/MS) when determining forchlorfenuron in apples, kiwis, and grapes. Both extraction methods gave recoveries of forchlorfenuron from fruits >70%. The QuEChERS method was cheaper, safer, and less time-consuming than the SPE method and can be recommended for routine analysis. The LOQ was 2 and 10 microg/kg for the LC/MS/MS and LC-UV analysis, respectively. The LOD was 1 and 5 microg/kg for the LC/MS/MS and LC-UV analysis, respectively. The sensitivity of the LC-UV analysis was adequate to measure residue levels five times lower than the maximum residue limit (MRL) of the product. The QuEChERS and SPE methods were applied to monitoring the persistence of forchlorfenuron in field-treated kiwis, and it was found that the residual concentration was already much lower than the MRL 7 days after treatment.

Evaluation of the field dissipation of fungicides and insecticides used on fruit bearing trees in northern Italy.

The dissipation of the fungicides captan, cyprodinil, fludioxonil, dithianon, and tebuconazole and of the insecticides chlorpyrifos, fenitrothion, and malathion was studied, following a single treatment of different cultivars of pears, apples, and peaches. The study was conducted in northern Italy, over two successive growing seasons (2004 and 2005). The treatments were performed by the farmers involved, in line with their usual practice. At various time intervals from treatment to harvest, representative samples of fruit were collected and analyzed for pesticide residues. In some cases, concentrations lower than the maximum residue levels (MRLs) were found immediately after treatment. In all trials a rapid decline in pesticide concentrations was observed leading to residues at harvest greatly below the MRLs.

Evaluation of the bioavailability of the herbicide prosulfocarb through adsorption on soils and model soil colloids, and through a simple bioassay.

Adsorption isotherms of prosulfocarb were determined on soils with different physicochemical properties. The extent of adsorption increased with the organic carbon content, but the results also suggested the involvement of some inorganic soil surfaces. In order better to understand the role of each soil surface, adsorption-desorption isotherms were determined on model soil colloids consisting of a soil humic acid, a montmorillonite, a synthetic aluminium hydroxide and their associations. The highest adsorption was observed on the humic acid, but it was also confirmed that the montmorillonite interacted with prosulfocarb. In contrast, the aluminium hydroxide was not active and its association with montmorillonite provoked a decrease in adsorption compared with montmorillonite alone. Except for humic acid, the highest adsorption took place on the ternary association montmorillonite-aluminium hydroxide-humic acid. On each surface tested, the adsorption was largely reversible and decreased at increasing pH. The herbicidal activity of prosulfocarb was tested by the determination of the germination and growth of a typical weed, Lolium multiflorum Lam, in contact with prosulfocarb solutions at different concentrations. The herbicide did not prevent the germination of the seeds but inhibited the growth of the roots and leaves. The same test was performed in the presence of the ternary system to evaluate the influence of adsorption on the plant bioavailability. It was concluded that the presence of an adsorptive surface reduced the herbicidal activity and that the simple bioassay proposed could be useful in predicting the extent of adsorption in a given soil.