Lucía Pareja

Detection of Pesticides in Active and Depopulated Beehives in Uruguay

The influence of insecticides commonly used for agricultural purposes on beehive depopulation in Uruguay was investigated. Honeycombs, bees, honey and propolis from depopulated hives were analyzed for pesticide residues, whereas from active beehives only honey and propolis were evaluated. A total of 37 samples were analyzed, representing 14,800 beehives. In depopulated beehives only imidacloprid and fipronil were detected and in active beehives endosulfan, coumaphos, cypermethrin, ethion and chlorpyrifos were found. Coumaphos was present in the highest concentrations, around 1,000 μg/kg, in all the propolis samples from active beehives. Regarding depopulated beehives, the mean levels of imidacloprid found in honeycomb (377 μg/kg, Standard Deviation: 118) and propolis (60 μg/kg, Standard Deviation: 57) are higher than those described to produce bee disorientation and fipronil levels detected in bees (150 and 170 μg/kg) are toxic per se. The other insecticides found can affect the global fitness of the bees causing weakness and a decrease in their overall productivity. These preliminary results suggest that bees exposed to pesticides or its residues can lead them in different ways to the beehive.

Study of the effects of operational parameters on multiresidue pesticide analysis by LC-MS/MS

In this paper, the influence of several operational parameters on a well established multiresidue LC-MS/MS method has been studied in relation to the analysis of 150 pesticides commonly present in vegetable samples. The operational parameters investigated are: (i) the influence of different modifiers (0.1% formic acid; 5mM ammonium formiate; 5mM ammonium acetate in aqueous phase) - both on the retention time and on the analytical response of the studied compounds; (ii) the effect of the analytical columns temperature on the retention time and on the analytical response of the pesticides investigated; (iii) the effects of co-elution in mixture containing 150 pesticides and, additionally, (iv) the carrying out of a study about the common transitions obtained by LC-MS/MS. Various common transitions were found among the 150 pesticides, but there were only two problematic cases, the pairs diuron-fluometuron and prometryn-terbutryn, which have common scanned transitions and have very close retention times. The use of ammonium salts as modifier instead of formic acid reports enhancement or suppression of the response depending on the pesticides. No great influence on the retention time or on the response of the pesticides and commodities studied was observed with relation to the column temperature. Two different columns: an HPLC (5 μm particle size) and an UHPLC analytical column (1.8 μm particle size) have been used. As was expected, shorter run times and lower peak width was achieved with the UHPLC column. In this paper, the effect of the compounds on each other in the MS analysis when the number of co-eluting compounds is quite high is also described. Mainly small suppression or enhancement co-elution effect was observed, but some particular pesticides presented high sensitivity (> ± 60% effect) when they elute together with others. This is an important factor and it has to be taken into account when performing multiresidue pesticide analysis.

Occurrence and distribution study of residues from pesticides applied under controlled conditions in the field during rice processing.

The results of an experiment to study the occurrence and distribution of pesticide residues during rice cropping and processing are reported. Four herbicides, nine fungicides, and two insecticides (azoxystrobin, byspiribac-sodium, carbendazim, clomazone, difenoconazole, epoxiconazole, isoprothiolane, kresoxim-methyl, propanil, quinclorac, tebuconazole, thiamethoxam, tricyclazole, trifloxystrobin, λ-cyhalotrin) were applied to an isolated rice-crop plot under controlled conditions, during the 2009-2010 cropping season in Uruguay. Paddy rice was harvested and industrially processed to brown rice, white rice, and rice bran, which were analyzed for pesticide residues using the original QuEChERS methodology and its citrate variation by LC-MS/MS and GC-MS. The distribution of pesticide residues was uneven among the different matrices. Ten different pesticide residues were found in paddy rice, seven in brown rice, and eight in rice bran. The highest concentrations were detected in paddy rice. These results provide information regarding the fate of pesticides in the rice food chain and its safety for consumers.

Comparison of extraction solvents and conditions for herbicide residues in milled rice with liquid chromatography-diode array detection analysis (LC-DAD)

Different extraction procedures and clean-up methods were compared in order to develop a sample preparation procedure for the multi-residue analysis of six post-emergence herbicides (metsulfuron methyl, bensulfuron methyl, pyrazosulfuron ethyl, bentazone, bispyribac sodium and cyhalofop butyl) in rice grains followed by liquid chromatography-diode array detection (LC-DAD). Optimum results were obtained dispersing milled rice grain in water, followed by the addition of 1% acetic acid in acetonitrile, MgSO4 and sodium acetate as a modification of the quick, easy, cheap, effective, rugged and safe (QuEChERS) method but no primary and secondary amine (PSA) sorbent was added due to the acidic nature of the herbicides. The method was further expanded to other post-emergence herbicides (quinclorac, clomazone and propanil). Except for quinclorac, which cannot be analysed with this method, the recoveries of the other eight herbicides were in the range 73–111%, with relative standard deviations lower than 12%. Limits of detection (LODs) ranged from 0.03 to 0.08 mg kg−1. A single analyst can extract twelve samples in 4 h. The method presented here allows the simultaneous residue determination of the most common post-emergence herbicides employed in cultivating rice. It is simple, rapid, sensitive, and can be applied routinely to polished rice grain herbicide residue analysis.

Simple Determination of 40 Organophosphate Pesticides in Raw Wool Using Microwave-Assisted Extraction and GC-FPD Analysis

A validated analytical method for the multiresidue analysis of 40 organophosphate pesticides (OPs) and conversion products in raw wool has been developed. The method is based on the selective microwave-assisted extraction (MAE) of raw wool with acetonitrile and analysis of extracts by gas chromatography-flame photometric detector. The optimum MAE conditions were 20 min duration at 80 °C with 30 mL of acetonitrile per gram of wool. A validation study was performed according to the European SANCO guidelines 10684/2009. Limits of detection and quantification for all pesticides tested were from 0.01 to 0.2 mg/kg and from 0.2 to 1.0 mg/kg, respectively. The average recoveries of pesticides spiked at different levels were in the range of 70-120% with relative standard deviations of ≤ 20%. The extraction performance was compared to the one obtained with a reference Soxhlet extraction. The method was also applied in the analysis of real wool (after field application) samples.

Transfer of pesticides to the brew during mate drinking process and their relationship with physicochemical properties.

In order to evaluate the extraction of pesticide residues that are transferred to the brew during mate drinking process of P.U.1 yerba mate leaves (Ilex paraguariensis), a special device to simulate the way in which mate is drunk in Uruguay was developed. The transfer to the brew of 12 organophosphates, 5 synthethic pyrethroids and one organochlorine pesticide from spiked samples was studied. The relationship between the transfer data thus obtained and physicochemical properties like water solubility (Ws), octanol-water coefficient (Kow) and Henrys constant (H) was evaluated. The extractability of the pesticide residues from yerba mate can be correlated with log Ws and log Kow. These transfer values allowed the calculation of ARLs (acceptable residue level) for the pesticides following Food and Agriculture Organization (FAO), World Health Organizaion (WHO) guidelines. These results can help the future establishment of maximum residue levels (MRLs)

Critical Revision and Development Perspectives of Herbicide Residues Analysis in Agro Ecosystems

Veronica Cesio1, Lucia Pareja1, Silvina Niell1, Lucia Geis Asteggiante1, Bernardo Bocking2, Claudio Garcia3, Grisel Fernandez4, Amadeo R. Fernandez-Alba5 and Horacio Heinzen1 1Farmacognosia y Productos Naturales, Facultad de Quimica UDELAR General Flores 2124, Montevideo 11800, 2Donistar S.C, Col. Rubio, Salto, 3INIA Las Brujas, Las Brujas, Canelones, 4Malherbologia EEMAC, Facultad de Agronomia, UDELAR Km366 Ruta 3 Paysandu, 5 Grupo de Investigacion de Laboratorio de Residuos de Plaguicidas, Almeria, Universidad de Almeria, Canada de San Urbano s/n, Almeria 1,2,3,4Uruguay 5Spain