Simultaneous determination of pesticides, biopesticides and mycotoxins in organic products applying a quick, easy, cheap, effective, rugged and safe extraction procedure and ultra-high performance liquid chromatography-tandem mass spectrometry

A method for the simultaneous determination of pesticides, biopesticides and mycotoxins from organic products was developed. Extraction of more than 90 compounds was evaluated and performed by using a modified QuEChERS-based (acronym of Quick, Easy, Cheap, Effective, Rugged, and Safe) sample preparation procedure. The method was based on a single extraction with acidified acetonitrile, followed by partitioning with salts, avoiding any clean-up step prior the determination by ultra-high performance liquid chromatography/tandem quadrupole mass spectrometry (UHPLC–MS/MS). Validation studies were carried out in wheat, cucumber and red wine as representative matrixes. Recoveries of the spiked samples were in the range between 70 and 120% (with intra-day precision, expressed as relative standard deviation, lower than 20%) for most of the analysed compounds, except picloram and quinmerac. Inter-day precision, expressed as relative standard deviation, was lower than 24%. Limits of quantification were lower than 10 μg kg⁻¹ and the developed method was successfully applied to the analysis of organic food products, detecting analytes belonging to the three types of compounds.     

Comparison of several extraction procedures for the determination of biopesticides in soil samples by ultrahigh pressure LC-MS/MS

A new procedure has been proposed for the determination of biopesticides (nicotine, sabadine, veratridine, rotenone, azadirachtin, cevadine, deguelin, spynosad D, and pyrethrins) and piperonyl butoxide in agricultural soils. Several extraction procedures such as solid-liquid extraction using mechanical shaking, sonication, pressurized liquid extraction, and modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) have been tested, obtaining better results when QuEChERS procedure without further cleanup steps was applied. The determination of the compounds was carried out by ultra high pressure liquid chromatography coupled to tandem mass spectrometry, using methanol and aqueous solution of ammonium formate 5 mM as mobile phase. The method was validated for all compounds at concentrations ranging from 10 to 100 μg/kg and recoveries ranged from 68 to 116%, except for nicotine and sabadine, with recoveries lower than 50%. Precision was estimated through intra- and inter-day studies, obtaining intra-day precision lower than 20% for most of the compounds, and inter-day precision was lower than 25%. Limits of detection and quantification were also estimated, obtaining limits of quantification equal or lower than 10 μg/kg. Finally, the method was applied to the analysis of 20 real agricultural soil samples and no biopesticide residues were found over the limit of quantification.     

Imaging cytoplasmic cAMP in mouse brainstem neurons

Background  

cAMP is an ubiquitous second messenger mediating various neuronal functions, often as a consequence of increased intracellular Ca²⁺ levels. While imaging of calcium is commonly used in neuroscience applications, probing for cAMP levels has not yet been performed in living vertebrate neuronal tissue before.     

Stable isotopic studies of earthworm feeding ecology in tropical ecosystems of Puerto Rico

Feeding strategies of earthworms and their influence on soil processes are often inferred from morphological, behavioral and physiological traits. We used (13)C and (15)N natural abundance in earthworms, soils and plants to explore patterns of resource utilization by different species of earthworms in three tropical ecosystems in Puerto Rico. In a high altitude dwarf forest, native earthworms Trigaster longissimus and Estherella sp. showed less (15)N enrichment ((15)N = 3-6 per thousand) than exotic Pontoscolex corethrurus ((15)N =7-9 per thousand) indicating different food sources or stronger isotopic discrimination by the latter. Conversely, in a lower altitude tabonuco forest, Estherella sp. and P. corethrurus overlapped completely in (15)N enrichment ((15)N = 6-9 per thousand), suggesting the potential for interspecific competition for N resources. A tabonuco forest converted to pasture contained only P. corethrurus which were less enriched in (15)N than those in the forest sites, but more highly enriched in (13)C suggesting assimilation of C from the predominant C(4) grass. These results support the utility of stable isotopes to delineate resource partitioning and potential competitive interactions among earthworm species. Copyright 1999 John Wiley & Sons, Ltd.