Luciano Vergori

Selective clean-up applicable to aqueous acetone extracts for the determination of carbendazim and thiabendazole in fruits and vegetables by high-performance liquid chromatography with UV detection

Fungicide residues in vegetables (benomyl, carbendazim, thiabendazole) are analyzed through a clean-up procedure that uses a portion of the aqueous acetone extract prepared for multiresidue methodology. A portion of the aqueous acetone extract (equivalent to 5 g of vegetables) is loaded onto an Extrelut-20 cartridge (the cartridge is filled with a coarse, large-pore diatomaceous material). Then, acetone is partially removed by an upward stream of nitrogen at 2l/min for 30 min. Benzimidazolic fungicides are recovered by percolating the cartridge with 100 ml of 0.1 M phosphoric acid solution, which also serves to convert benomyl to carbendazim. The percolating acid solution is drained on-line through a strong cation-exchange (SCX) solid-phase extraction cartridge with the aid of a slight vacuum. Benzimidazolic fungicides are retained on the SCX cartridge. The phosphoric acid solution is discarded together with the washings of the SCX cartridge, i.e., water followed by methanol-water (75:25), that remove unwanted coextractives. Finally, benzimidazolic fungicides are recovered by eluting the SCX cartridge with methanol-ammonium formate buffer (75:25). The final extract is then analyzed by reversed-phase HPLC with UV detection. Recoveries from crops such as apples, lettuce, strawberries and citrus fruits are generally greater than 80% and no interferences were observed. The clean-up is simple and straightforward, requires only disposable items, water solutions and a few milliliters of solvent and a minimum number of manipulations, and does not require concentration steps or electrical equipment.

Determination of pyrethroid pesticide residues in fatty materials by solid-matrix dispersion partition followed by mini-column, size-exclusion chromatography

The method studied uses a combination of a solid-matrix dispersion partition (SMDP) followed by high-performance size-exclusion chromatography on a minicolumn (HPmSEC) of 7.8 mm I.D. for the separation of pyrethroid (PYR) residues from fatty material. The solid-matrix dispersion extraction is carried out by absorbing a fat solution onto an Extrelut-3 cartridge (filled with a macroporous diatomaceous material) and extracting the PYR residues with acetonitrile. Up to 1 g of fatty material can be extracted with 15 ml acetonitrile. The small amount (mean +/- S.D. = 12.4 +/- 5.9 mg) of fatty material which is eluted into the acetonitrile is further removed by HPmSEC. PYR pesticide residues are collected in a 2-ml fraction between 7 and 9 ml, the column being washed up to 24 ml. The two techniques used in series allow a better removal of fat, a greater input of sample and a lower consumption of solvent compared to the sole SEC on macrocolumns, and a lower limit of determination compared to the sole SEC on minicolumns. Recoveries of 9 PYR out of the 14 investigated residues from soya oil were in the range 66-83% at spiking levels ranging 0.49-2.57 mg/kg, while for 6 PYR residues tested at spiking levels in the range 0.13-0.53 mg/kg the recoveries were in the range 80-111%. Recovery of fluvalinate and permethrin could not be calculated due to interferences from soya oil, while lambda-cyhalothrin, esfenvalerate and tralomethrin gave low recovery. The final extract contains small amount (mean +/- S.D. = 2.4 +/- 0.9 mg) of lipid residue and is not completely free from interferences.

Application of solid-phase partition cartridges in the determination of fungicide residues in vegetable samples

Disposable, ready-to-use cartridges filled with a macroporous diatomaceous material are used to extract in a single step fungicide residues with dichloromethane from aqueous acetone extracts of vegetables. This procedure takes the place of some functions (such as separating funnel partition, drying over anhydrous sodium sulphate and clean-up) usually performed by separate steps in classical schemes. Fourteen fungicides (dichloran, vinclozolin, chlorthalonil, triadimefon, dichlofluanide, procymidone, hexaconazole, captan, folpet, ditalimfos, iprodione, captafol, pyrazophos and fenarimol) were determined using the described procedure with recoveries between 83 and 107% at spiking levels ranging for the different compounds from 0.04 to 0.40 mg/kg. Crops subjected to the described procedure included lettuce, strawberry, apple, yellow pepper and peach, and gave extracts containing a mass of co-extractives between 5 and 30 mg. Compared with classical schemes, the described procedure is simple, less labour intensive, allows parallel handling of several extracts and does not require preparation and maintenance of equipment. Troublesome emulsions such as those frequently observed in separating funnel partitioning do not occur.

Clean-up procedure for the extraction of soil samples in the determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin.

This paper describes the method which was developed in relation to analytical work connected with microbial and physico-chemical degradation experiments on 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Soil samples are best extracted with methanol plus methylene chloride. Microbial preparations are extracted with light petroleum after boiling with methanolic potassium hydroxide. The clean-up consists of a sulphuric acid treatment and chromatography on a multilayer column (Celite + H2SO4/silica gel) followed by alumina column chromatography. The clean-up procedure proved to be suitable for soil samples and microbial preparations even when large quantities of organic matter (hydrocarbons, oils, surfactants) were present.

Screening for coumatetralyl in soft drinks by solid-matrix extraction and high-performance liquid chromatography with diode-array detection.

A method was developed for the rapid determination coumatetralyl in cola- and orange-type soft drinks, which includes extraction using solid-matrix column, clean-up by silica cartridge chromatography and reversed-phase high-performance liquid chromatography with diode-array detection. The recovery of coumatetralyl from 50 ml of soft drinks was better than 80% at spiking levels down to 50 micrograms/kg (ppb).

LABORATORY INVESTIGATION FOR THE MICROBIOLOGICAL DEGRADATION OF 2,3,7,8-TETRACHLORODIBENZO-p-DIOXIN IN SOIL BY ADDITION OF ORGANIC COMPOST

ABSTRACT The persistence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in soil has been studied under laboratory conditions. The effect of addition to the soil of an organic compost rich in both organic matter and microbial flora has been investigated in the soil from Seveso, accidentally polluted by TCDD and in a TCDD free soil to which a known amount of TCDD was applied. In both experiments the initial concentration of TCDD was at level of 0.1 mg/Kg. The TCDD was periodically monitored over 480 days. At this time 73% to 77% of the initially present TCDD was recovered in both experiments. Data show that the addition of organic compost had no appreciable influence on the degradation of TCDD. Soil samples were extracted with methanol followed by dichloromethane and the extracts were cleaned-up by column chromatography. Determination of TCDD was carried out by GLC/ECD and confirmed by GLC/MS.

Residue Levels in Apples and Pears Field-Treated with Two Experimental Chlorothalonil Formulations

Chlorothalonil is a well-known product largely used in several countries against a broad spectrum of pathogenic fungi which affect economically important crops (I, 2, 3). Chlorothalonil has been recently considered by I.A.R.C. (4). In Italy, Chlorothalonil is included in a list of pesticides presently under revision. A deeper and updated knowledge about its toxicological and environmental properties will improve the evaluation of risks related to the use of that pesticide. In this framework t he determination of the residues in crops treated with Chlorothalonil formulations was performed. As new types of Chlorothalonil formulations become available, itis essential to check both their efficacy and their residue levels after treatment. Two different types of experimental Chlorothalonil formulations bave been tested in a field treatment carried out by the Regional Plant Protection Service (Bologna, Italy) on apple and pears cultivations. This paper presents the levels of Chlorothaloni! residues in treated apple and pear samples, harvested afte�9 several time intervals, under the experimenta! conditions described below.

Lack of in vitro oxidation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the presence of laccase from Polyporus versicolor fungus

Abstract An investigation has been carried out to assess whether Polyporus versicolor laccase could catalyze in vitro transformation of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) under a number of different experimental conditions of incubation including homogeneous or heterogeneous phase, variable durations, addition of phenol, variable dissolved oxygen concentrations and TCDD/laccase ratios. No significant degradation of TCDD was detected.