J. Mañes

Determination of pesticide residues in fruit and vegetables

A review concerning the determination of pesticide residues in fruit and vegetables is presented. The basic principles and recent developments in the extraction and quantitation of pesticides are discussed. Consideration is given to solid phase and supercritical extraction techniques, automation and robotic systems, and immunoassay procedures.

Determination of carbamate residues in fruits and vegetables by matrix solid-phase dispersion and liquid chromatography-mass spectrometry.

Thirteen carbamates were analysed in orange, grape, onion and tomatoes by matrix solid-phase dispersion (MSPD) followed by liquid chromatography-mass spectrometry (LC-MS). Electrospray (ES) and atmospheric pressure chemical ionisation (APCI) were compared and both gave similar results in terms of sensitivity and structural information because at 20 V fragmentor voltages the fragmentation is minimal. The efficiency of different solid-phases (C18, C8, cyano, amine and phenyl) for the MSPD was compared. Mean recoveries using C8 varied from 64 to 106% with relative standard deviations of 5-15% in the concentration range of 0.01-10 mg kg(-1). Matrix constituents did not interfere significantly with the ionisation process of carbamates. The limits of detection were typically in the 0.001-0.01 mg kg(-1) range, which were between 10 and 100 times lower than the maximum residue levels (MRLs) established by the European Union (EU). The method was applied to residue detection in fruit and vegetable samples taken from Valencian markets, in which carbamates were detected at low concentrations.

Solid-phase extraction in multi-residue pesticide analysis of water

The determination of pesticides in water is fundamental to the solution of environmental problems as natural waters are usually contaminated with a large number of pesticides. The selection of an isolation and/or concentration technique depends largely on the class of pesticides to be determined. It is often necessary to determine simultaneously a wide variety of compounds in a water sample. Application of solid-phase extraction techniques offers a solution. The mechanisms of solid-phase extraction, types of sorbents and their application to multi-residue pesticide analysis are reviewed.

Pesticide residue determination in fruit and vegetables by liquid chromatography-mass spectrometry

An overview is given of pesticide residue determination in fruit and vegetables by liquid chromatography-mass spectrometry (LC-MS). Emphasis is placed on the thermospray, particle beam and atmospheric pressure ionization interfaces including advantages and drawbacks and typical detection limits. The capacity of each interface to provide useful data for identification/confirmation of analytes and the possibility of obtaining structural information for the identification of target and non-target compounds is discussed. Finally, sample preparation techniques are dealt with in relation to their influence on further LC-MS determination.

Determination of aflatoxins in peanuts by matrix solid-phase dispersion and liquid chromatography ☆

A new method based on matrix solid-phase dispersion (MSPD) extraction was studied to determine aflatoxin B1, B2, G1 and G2 from peanuts. Optimization of different parameters, such as type of solid supports for matrix dispersion and elution solvents were carried out. The method used 2 g of peanut sample, 2 g of C18 bonded silica as MSPD sorbent and acetonitrile as eluting solvent. Recoveries of each aflatoxin spiked to peanut samples at 2.5 ng/g (5 ng/g for aflatoxin G2) level were between 78 and 86% with relative standard deviations ranging from 4 to 7%. The limits of quantification ranged from 0.125 to 2.5 ng/g for the four studied aflatoxins using liquid chromatography (LC) with fluorescence detection. In addition, LC coupled to mass spectrometry with an electrospray interface was used for confirmation of aflatoxins present in real samples. Eleven peanut samples from different countries were analyzed by the proposed method and by using an enzyme-linked immunosorbent assay (ELISA). ELISA test is a good screening method for investigation of these mycotoxins in peanut samples.

Dietary Administration of High Doses of Pterostilbene and Quercetin to Mice Is Not Toxic

The aim of this study is to evaluate possible harmful effects of high doses of t-pterostilbene (t-PTER) and quercetin (QUER) in Swiss mice. Mice were fed during 28 days at doses of 0, 30, 300, and 3000 mg/kg body weight/day of t-PTER, QUER, or a mixture of both, t-PTER + QUER, which are equivalent to 5, 50, and 500 times, respectively, the estimated mean human intake of these polyphenols (25 mg/day). Daily oral administration of QUER, t-PTER, or a mixture of both of them did not cause mortality during the experimental period. There were no differences in food and water consumption on sex. No significant body weight gain in the male or female groups was observed. Red blood cell number and the hematocrit increased after polyphenols administration compared to control groups. Biochemical parameters were not affected. Histopathological examination revealed no alterations in clinical signs or organ weight at any dose.

Assessment of the microbiological quality and wash treatments of lettuce served in University restaurants.

One hundred and forty-four samples of lettuce from 16 University restaurants were analyzed. The mesophilic aerobic counts of all samples ranged from 3.01 to 7.81 log10 CFU g(-1). Results of total coliforms ranged from < 0.47 to > 3.38 log10 most probable number (MPN) g(-1). Of the lettuce samples, 25.7% harbored Escherichia coli, 22.9% Staphylococcus aureus and 84% group D streptococci. Similarly, 10.4% of the samples harbored Aeromonas hydrophila, 2.8% Pseudomonas aeruginosa, and coliforms such as 14.6% Citrobacter freundii, 8.3% Klebsiella pneumoniae, 4.2% Enterobacter cloacae and 1.4% Providencia spp. Salmonella, Shigella and E. coli O157:H7 were not detected. When sodium hypochlorite or potassium permanganate solutions were used in washing procedures, the aerobic microorganisms were reduced by more than two log units, and total coliforms by at least one log.

Determination of triazines and organophosphorus pesticides in water samples using solid-phase extraction

Octadecyl (C18)-bonded porous silica was evaluated for the extraction of triazine and organophosphorus pesticides from natural water. The extraction results showed an effective performance when 11 of water was passed through small glass columns containing 500 mg of 50-100-microns C18 bonded porous silica. The adsorbed compounds were removed with ethyl acetate, evaporated to 200 microliters and determined by gas chromatography. The overall average recoveries were greater than 85% except for dimethoate and trichlorfon. Application of this procedure to the analysis of natural water samples gave results that agree well with those obtained by solvent extraction methods.

Determination of fungicide residues in fruits and vegetables by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A liquid chromatography (LC) method for the quantitative determination of five fungicide residues (dichloran, flutriafol, o-phenylphenol, prochloraz and tolclofos methyl) in oranges, lemons, bananas, peppers, chards and onions is described. The residues were extracted by matrix solid-phase dispersion (MSPD) using C8. Quantitative analysis was performed by isocratic LC coupled to quadrupole mass spectrometer using atmospheric pressure chemical ionization in the negative ionization mode. The limit of quantification was 0.01 mg kgmicro for flutriafol, o-phenylphenol and dichloran, and 0.1 mg kg(-1) for prochloraz and tolclofos methyl. The MSPD method is also suitable for LC-UV analysis but higher limits of quantification (between 1 and 5 mg kg(-1)) were obtained. Validation of the method was performed between 0.01 and 25 mg kg(-1). Recoveries for fungicides ranged from 52.5 to 91.1% with relative standard deviations between 6.1 and 11.9%. The method was applied to the determination of residues in samples taken from agricultural cooperatives. The fungicides most often detected were o-phenylphenol and prochloraz.

Analytical Methods for Pesticide Residue Determination in Bee Products

Monitoring pesticide residues in honey, wax, and bees helps to assess the potential risk of these products to consumer health and gives information on the pesticide treatments that have been used on the field crops surrounding the hives. The present review seeks to discuss the basic principles and recent developments in pesticide analysis in bee products and their application in monitoring programs. Consideration is given to extraction, cleanup, chromatographic separation, and detection techniques.