a b s t r a c tA total of 13,556 samples of 22 fruit and vegetable crops, rice, and beans were analyzed within two Brazilian pesticide residue monitoring programs between 2001 and 2010. Pesticide residues were found in 48.3% of the samples, and 13.2% presented some irregularity, mostly non-authorized active ingredient use. Less than 3% of the samples had residue levels above the MRL. Apple, papaya, sweet pepper and strawberry were the crops with the higher percentages of positive samples (about 80%). Dithiocarbamates and organophosphorus compounds were found in 41.6% and 30.8% of the samples, respectively. Carbendazim and chlorpyrifos were the pesticides most found (26.7 and 16.1% of positive samples, respectively). Almost half of the samples analyzed had multiple residues (up to 10 residues), with multiple residues most common in samples of apple, sweet pepper and tomato. About 8% of positive samples contained up to four residues of the same chemical class, mainly organophosphorus compounds (18.6%, mostly in apple) and triazoles (16.1%, mostly in papaya and grape). In general, the scenario of pesticide residues in foods investigated within the Brazilian governmental monitoring programs in the last decade is similar to what has been found in other countries. However, the use of non-authorized active ingredients is a common practice among the farmers in the country, a problem that the government authorities have been trying to solve. A preliminary cumulative acute exposure assessment for organophosphates and carbamates in apple has shown that the intake by individuals 10 years old accounts for 100% of the acephate ARfD, indicating a need to further investigate the exposure through the consumptions of other crops and group of pesticides, mainly for children.
Dithiocarbamates are a class of fungicides extensively used in many crops worldwide. The current residue definition of dithiocarbamates in food for compliance with maximum residue limits, at national and international levels, is total residues arising from the use of any or each dithiocarbamate fungicide, determined as CS(2). The analytical method most frequently used to analyze dithiocarbamate residues in food for monitoring purposes was proposed more than 30 years ago. In this method, total dithiocarbamates are decomposed to CS(2), which is purified and reacted with a cupric reagent. The yellow complex formed is quantified by spectrophotometry. In this paper, a new reaction system for the purification and complexation of CS(2) is proposed. The new system is less fragile than the traditional design, is easier to assemble, and allows for a higher sample throughput, in addition to being of low cost. Recovery of added mancozeb, thiram, or ziram (0.15-8.0 mg/kg) in rice, beans, apple, banana, orange, papaya, tomato, cucumber, and potato ranged from 82 to 120%, with relative standard deviations from 0 to 10% (n = 3 or 5). Analysis of apple, tomato, and papaya samples with field-incurred dithiocarbamate residues showed comparable results using both the traditional and the new reaction systems.
The biosynthesis of the sphinganine analogue mycotoxins (SAMs) fumonisin B1 and the AAL toxins
was studied by growing Fusarium
moniliforme and Alternaria alternata f. sp. lycopersici in liquid
culture. Radioactive and stable isotopically labeled amino acid, water, and molecular oxygen
precursors were added to the culture media and toxins were analyzed using thin-layer chromatography, liquid scintillation counting, high-performance liquid chromatography (HPLC), 13C nuclear
magnetic resonance (NMR) spectroscopy, and electrospray mass spectrometry (ESMS). Results
indicated that glycine was incorporated directly into the AAL toxins and that methionine was
incorporated into the AAL toxin methyl groups. Oxygens in tricarballylic acid moieties for fumonisin
B1 and the AAL toxins were derived from H2O while the lipid backbone hydroxyls for fumonisin B1
and the AAL toxins originated from molecular oxygen. Isotopic enrichment patterns for the various
AAL toxins showed marked differences among toxins, suggesting a complex, rather than sequential,
Keywords: Mycotoxins; sphinganine analogue mycotoxins; isotope enrichment
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