288 research outputs found
Determination of pesticide residues in olives by liquid extraction surface analysis followed by liquid chromatography/tandem mass spectrometry
Automated Mini-Column Solid-Phase Extraction Cleanup for High-Throughput Analysis of Chemical Contaminants in Foods by Low-Pressure Gas ChromatographyâTandem Mass Spectrometry
Ruptured abdominal aortic aneurysm, a âtwo-hitâ ischemia/reperfusion injury: Evidence from an analysis of oxidative products
AbstractPurpose: Ruptured abdominal aortic aneurysm (RAAA) remains a lethal condition despite improvements in perioperative care. The consequences of RAAA are hypothesized to result from a combination of two ischemia/reperfusion events: hemorrhagic shock and lower torso ischemia. Ischemia/reperfusion results in tissue injury by diverse mechanisms, which include oxygen free radicalâmediated injury produced from activated neutrophils, xanthine oxidase, and mitochondria. Oxygen-free radicals attack membrane lipids, resulting in membrane and subsequently cellular dysfunction that contributes to postoperative organ injury/failure. The purpose of this investigation was to quantify the oxidative injury that occurs as a result of the ischemia/reperfusion events in RAAAs and elective AAAs. Methods: Blood samples were taken from 22 patients for elective AAA repair and from 14 patients for RAAA repair during the perioperative period. Plasma F2 -isoprostanes were extracted, purified, and measured with an enzyme immunoassay. Aldehydes and acyloins were purified and quantified. Neutrophil oxidative burst was measured in response to a receptor independent stimulus (phorbol 12-myristate 13-acetate) with luminol-based chemiluminescence. Results: Plasma from patients with RAAAs showed significantly elevated F2 -isoprostane levels on arrival at hospital and were significantly elevated as compared with the levels of patients for elective repair throughout the perioperative period (two-way analysis of variance, P < .0001). Multiple regression showed a significant relationship between the phagocyte oxidative activity and F2 -isoprostane levels (P < .013). Total acyloin levels were significantly higher in patients with RAAAs as compared with the levels in elective cases. Conclusion: The F2 -isoprostane levels, specific markers of lipid peroxidation, showed that patients with RAAAs had two phases of oxidative injury: before arrival at hospital and after surgery. The significant relationship between the postoperative increases in F2 -isoprostane levels and the neutrophil oxidant production implicates neutrophils in the oxidative injury that occurs after RAAA. New therapeutic interventions that attenuate neutrophil-mediated oxidant injury during reperfusion may decrease organ failure and ultimately mortality in patients with RAAAs. (J Vasc Surg 1999;30:219-28.
Evaluation of the QuEChERS Method and Gas ChromatographyâMass Spectrometry for the Analysis Pesticide Residues in Water and Sediment
A method for the determination of pesticide residues in water and sediment was developed using the QuEChERS method followed by gas chromatography â mass spectrometry. The method was validated in terms of accuracy, specificity, linearity, detection and quantification limits. The recovery percentages obtained for the pesticides in water at different concentrations ranged from 63 to 116%, with relative standard deviations below 12%. The corresponding results from the sediment ranged from 48 to 115% with relative standard deviations below 16%. The limits of detection for the pesticides in water and sediment were below 0.003 mg Lâ1 and 0.02 mg kgâ1, respectively
Modification and re-validation of the ethyl acetate-based multi-residue method for pesticides in produce
The ethyl acetate-based multi-residue method for determination of pesticide residues in produce has been modified for gas chromatographic (GC) analysis by implementation of dispersive solid-phase extraction (using primaryâsecondary amine and graphitized carbon black) and large-volume (20Â ÎźL) injection. The same extract, before clean-up and after a change of solvent, was also analyzed by liquid chromatography with tandem mass spectrometry (LCâMSâMS). All aspects related to sample preparation were re-assessed with regard to ease and speed of the analysis. The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades. The modifications were made with techniques currently commonly applied in routine laboratories, GCâMS and LCâMSâMS, in mind. The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person. Limits of quantification (LOQs) of 0.01Â mg kgâ1 were achieved with both GCâMS (full-scan acquisition, 10Â mg matrix equivalent injected) and LCâMSâMS (2Â mg injected) for most of the pesticides. Validation data for 341 pesticides and degradation products are presented. A compilation of analytical quality-control data for pesticides routinely analyzed by GCâMS (135 compounds) and LCâMSâMS (136 compounds) in over 100 different matrices, obtained over a period of 15Â months, are also presented and discussed. At the 0.05Â mg kgâ1 level acceptable recoveries were obtained for 93% (GCâMS) and 92% (LCâMSâMS) of pesticideâmatrix combinations
Qualitative aspects and validation of a screening method for pesticides in vegetables and fruits based on liquid chromatography coupled to full scan high resolution (Orbitrap) mass spectrometry
The analytical capabilities of liquid chromatography with single-stage high-resolution mass spectrometry have been investigated with emphasis on qualitative aspects related to selective detection during screening and to identification. The study involved 21 different vegetable and fruit commodities, a screening database of 556 pesticides for evaluation of false positives, and a test set of 130 pesticides spiked to the commodities at 0.01, 0.05, and 0.20 mg/kg for evaluation of false negatives. The final method involved a QuEChERS-based sample preparation (without dSPE clean up) and full scan acquisition using alternating scan events without/with fragmentation, at a resolving power of 50,000. Analyte detection was based on extraction of the exact mass (Âą5 ppm) of the major adduct ion at the database retention time Âą30 s and the presence of a second diagnostic ion. Various options for the additional ion were investigated and compared (other adduct ions, Mâ+â1 or Mâ+â2 isotopes, fragments). The two-ion approach for selective detection of the pesticides in the full scan data was compared with two alternative approaches based on response thresholds. Using the two-ion approach, the number of false positives out of 11,676 pesticide/commodity combinations targeted was 36 (0.3 %). The percentage of false negatives, assessed for 2,730 pesticide/commodity combinations, was 13 %, 3 %, and 1 % at the 0.01-, 0.05-, and 0.20-mg/kg level, respectively (slightly higher with fully automated detection). Following the SANCO/12495/2011 protocol for validation of screening methods, the screening detection limit was determined for 130 pesticides and found to be 0.01, 0.05, and âĽ0.20 mg/kg for 86, 30, and 14 pesticides, respectively. For the detected pesticides in the spiked samples, the ability for unambiguous identification according to EU criteria was evaluated. A proposal for adaption of the criteria was made
Movement of Soil-Applied Imidacloprid and Thiamethoxam into Nectar and Pollen of Squash (Cucurbita pepo)
There has been recent interest in the threat to bees posed by the use of systemic insecticides. One concern is that systemic insecticides may translocate from the soil into pollen and nectar of plants, where they would be ingested by pollinators. This paper reports on the movement of two such systemic neonicotinoid insecticides, imidacloprid and thiamethoxam, into the pollen and nectar of flowers of squash (Cucurbita pepo cultivars âMultipik,â âSunrayâ and âBush Delicataâ) when applied to soil by two methods: (1) sprayed into soil before seeding, or (2) applied through drip irrigation in a single treatment after transplant. All insecticide treatments were within labeled rates for these compounds. Pollen and nectar samples were analyzed using a standard extraction method widely used for pesticides (QuEChERS) and liquid chromatography mass spectrometric analysis. The concentrations found in nectar, 10Âą3 ppb (mean Âą s.d) for imidacloprid and 11Âą6 ppb for thiamethoxam, are higher than concentrations of neonicotinoid insecticides in nectar of canola and sunflower grown from treated seed, and similar to those found in a recent study of neonicotinoids applied to pumpkins at transplant and through drip irrigation. The concentrations in pollen, 14Âą8 ppb for imidacloprid and 12Âą9 ppb for thiamethoxam, are higher than those found for seed treatments in most studies, but at the low end of the range found in the pumpkin study. Our concentrations fall into the range being investigated for sublethal effects on honey bees and bumble bees
Pesticide residues in Portuguese strawberries grown in 2009â2010 using integrated pest management and organic farming
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