► Seven neonicotinoids were simultaneously determined in beeswax for the first time. ► The usefulness of fused-core columns to separate neonicotinoids was demonstrated. ► The sample clean-up was ...performed onto diatomaceous based cartridges. ► Matrix (beeswax) had an influence (ion suppression) onto the ESI-MS signals. ► Residues of thiamethoxam, acetamiprid and imidacloprid were found in 11 samples.
A new method has been developed to measure seven neonicotinoid insecticides (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid and thiamethoxam) in beeswax using liquid chromatography (LC) coupled to electrospray ionization mass spectrometry (ESI-MS) detection. Beeswax was melted and diluted in an n-hexane/isopropanol (8:2, v/v) mixture. After this, liquid extraction with water was performed followed by a clean-up on diatomaceous material based cartridges. The compounds were eluted with acetone, and the resulting solution was evaporated until dry and reconstituted with a mixture of water and acetonitrile 50:50 (v/v). The separation of all compounds was achieved in less than 15min using a C18 reverse-phase fused-core column (Kinetex® C18, 150mm×4.6mm i.d.) and a mobile phase composed of a mixture of 0.1% formic acid in water and acetonitrile in gradient elution mode at 0.5mL/min. This method was fully validated in terms of selectivity, linearity, precision and recovery. Low limits of detection and quantification could be achieved for all analytes ranging from 0.4 to 2.3μg/kg, and from 1.5 to 7.0μg/kg, respectively. Finally, the proposed method was applied to an analysis of neonicotinoid residues in beeswax samples from apiaries located close to fruit orchards.
•Calculation of diesel rate of fuel injection through momentum flux measurements is applied.•This novel alternative method have been applied to different fossil and renewable fuels.•Wide range of ...diesel fuels has been tested: Diesel, GTL, Farnesane and Biodiesel fuels.•The method has been tested under different operating conditions of diesel injection process.•This novel application of the method has been also tested under single and split fuel injection.
Due to environmental problems, research on fuel economy and pollutant emissions in internal combustion engines has drawn the attention of automobile manufacturers and researchers. The diesel engine is one of the most efficient alternatives and one of the main areas of the study in these engines is spray mixing, recognized as a critical factor in combustion control and the reduction of its related contaminants.
The studies about fuel sprays rely on experimental data of the rate of injection, which can only be obtained with high-cost equipment. The aim of this paper is to validate for different fuels a method for the determination of the rate of injection based on spray momentum measurements and the total injected mass. After a proper tuning of the test momentum flux device, the injection rate results were validated using the Bosch tube method. The technique was validated for four different fuels, diesel, biodiesel, GTL (Gas-to-liquid) and Farnesane, in order to identify the consequences of the fuel properties on the injection performance characteristics and the estimation method.
The results of rate of injection following the procedures presented showed good accuracy when compared to experimental values. These methods can be employed to estimate this parameter when experimental facilities for this purpose are not available.
Multiple sclerosis lesions develop around small veins that are radiologically described as the so-called central vein sign. With 7T MR imaging and magnetic susceptibility-based sequences, the central ...vein sign has been observed in 80%-100% of MS lesions in patients' brains. However, a lower proportion ∼50% has been reported at 3T using susceptibility-weighted angiography (SWAN). Our aim was to assess a modified version of SWAN optimized at 3T for sensitive detection of the central vein sign.
Thirty subjects with MS were scanned on a 3T clinical MR imaging system. 3D T2-weighted FLAIR and optimized 3D SWAN called SWAN-venule, were acquired after injection of a gadolinium-based contrast agent. Patients showing >3 focal white matter lesions were included. The central vein sign was recorded by 2 trained raters on SWAN-venule images in the supratentorial brain.
Twenty patients showing >3 white matter lesions were included. A total of 380 white matter lesions (135 periventricular, 144 deep white matter, and 101 juxtacortical) seen on both FLAIR and SWAN-venule images were analyzed. Overall, the central vein sign was detected in 86% of the white matter lesions (periventricular, 89%; deep white matter, 95%; and juxtacortical, 78%).
The SWAN-venule technique is an optimized MR imaging sequence for highly sensitive detection of the central vein sign in MS brain lesions. This work will facilitate the validation and integration of the central vein sign to increase the diagnostic certainty of MS and further prevent misdiagnosis in clinical practice.
First testing of the CALIFA Barrel Demonstrator Pietras, B.; Winkel, M.; Alvarez-Pol, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2016, Volume:
814
Journal Article
Peer reviewed
Open access
Advancement of the CALIFA calorimeter project has reached a new milestone with the construction of the first modules of the CALIFA Demonstrator, ultimately to be integrated into the final ...calorimeter. Aspects and methods of detector optimisation will be discussed, along with characterisation using proton beams of 70<Ekin<230MeV at the Bronowice Cyclotron Centre (CCB) in Krakow, Poland. Features such as the support structure, crystal geometry and digital electronics represent the final versions to be employed, enabling a full test of each component׳s performance. A study of caesium iodide quenching over the available proton energy range has been performed, to accompany a method for proton calibration scaled from the measured gamma-ray energies.
Here, a measurement of the 8B solar neutrino flux has been made using a 69.2 kt-day dataset acquired with the SNO+ detector during its water commissioning phase. At energies above 6 MeV the dataset ...is an extremely pure sample of solar neutrino elastic scattering events, owing primarily to the detector’s deep location, allowing an accurate measurement with relatively little exposure. In that energy region the best fit background rate is 0.25+0.09–0.07 events/kt–day, significantly lower than the measured solar neutrino event rate in that energy range, which is 1.03+0.13–0.12 events/kt–day. Also using data below this threshold, down to 5 MeV, fits of the solar neutrino event direction yielded an observed flux of 2.53+0.31–0.28(stat)+0.13–0.10(syst) × 106 cm–2 s–1, assuming no neutrino oscillations. This rate is consistent with matter enhanced neutrino oscillations and measurements from other experiments.
This paper reports the preparation of the first dual electrochemical immunosensor for the simultaneous determination of the CXCL7 chemokine and the MMP3 metalloproteinase as relevant biomarkers for ...the better diagnosis and monitoring of rheumatoid arthritis derived from the multiple biomarkers measurement. The developed immunosensor involves the use of carboxylated magnetic beads (MBs) and dual screen-printed carbon electrodes (SPdCEs). Sandwich-type configurations implied the covalent immobilization of specific anti-CXCL7 (cAb1) or anti-MMP3 (cAb2) capture antibodies onto MBs and the use of biotinylated detection antibodies with further labelling with HRP-Strept conjugates. The resulting MBS bioconjugates were magnetically captured on the respective working electrode of the SPdCE and the determination of the antigens was accomplished by measuring the amperometric responses of H2O2 mediated by hydroquinone (HQ) at a potential value of −0.20 V. The dual immunosensor provided calibration plots with linear ranges between 1 and 75 ng mL−1 (CXCL7) (R2 = 0.997) and from 2.0 to 2000 pg mL−1 (MMP3) (R2 = 0.998) with detection limits of 0.8 ng mL−1 and 1.2 pg mL−1, respectively. The assay took 2 h 20 min for the simultaneous determination of both biomarkers. The dual immunosensor was successfully applied to the analysis of human serum from positive and negative RA patients.
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•First immunosensor for simultaneous determination of CXCL7 and MMP3 biomarkers.•Sandwich immunoassay using magnetic microparticles to immobilize capture antibodies.•Amperometry at screen-printed carbon electrodes using hydroquinone/hydrogen peroxide.•Detection limits of 0.8 ng mL−1 (CXCL7) and 1.2 pg mL−1 (MMP3).•Analysis of serum from healthy individuals and patients with rheumatoid arthritis.
Simultaneous determination of fertility hormones in saliva using disposable immunosensing platforms and a custom designed field-portable dual potentiostat.
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•Simultaneous determination ...of progesterone and luteinizing hormone in saliva samples.•Disposable immunoplatforms and custom designed field-portable dual potentiostat.•LODs of 1.7 pg mL−1 and 0.10 mIU mL-1 for P4 and LH, respectively, in less than 1 h.•Accurate determination of both target hormones in saliva samples.
This work describes a new electroanalytical device for the simultaneous and reliable determination of two fertility relevant hormones (luteinizing hormone, LH, and progesterone, P4) in saliva. The device is constructed using a custom designed and field-portable potentiostat where dual disposable immunosensing platform are connected. The immunosensors are based on sandwich-type and competitive immunoassays implemented onto magnetic microbeads (MBs) functionalized with Neutravidin and Protein G for the determination of LH and P4, respectively. Amperometric detection performed at −0.20 V vs the Ag pseudo-reference electrode using the H2O2/hydroquinone (HQ) system was employed as the transduction technique after placing the MBs with immunocomplexes for each target hormone on the appropriate working electrode of screen-printed dual carbon electrodes (SPdCEs). The method exhibits high sensitivity and selectivity for the target hormones providing detection limits of 1.7 pg mL−1 and 0.10 mIU mL−1 for P4 and LH, respectively, with a 1 h test time. The applicability of the method was confirmed by determining both hormones in saliva samples from different volunteers providing results comparable to those obtained using amperometric transduction with a commercial potentiostat and with ELISA methodologies involving the same immunoreagents for each target hormone.
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•The role of biosensors in forensic analysis is critically reviewed.•The different transduction modes of the biorecognition event are considered.•The target analytes involved in ...forensic toxicological analysis are treated.•Biosensors useful for detection of chemical and biological weapons are commented.•Tables with the characteristics of biosensors for forensic analysis are provided.
Forensic analysis is an important branch of modern Analytical Chemistry with many legal and socially relevant implications. Biosensors can play an important role as efficient tools in this field considering their well known advantages of sensitivity, selectivity, easy functioning, affordability and capability of miniaturization and automation. This article reviews the latest advances in the use of biosensors for forensic analysis. The different methodologies for the transduction of the produced biological events are considered and the applications to forensic toxicological analysis, classified by the nature of the target analytes, as well as those related with chemical and biological weapons critically commented. The article provides several Tables where the more relevant analytical characteristics of the selected reported methods are gathered.
Dual screen-printed carbon electrodes modified with 4-carboxyphenyl-functionalized double-walled carbon nanotubes (HOOC-Phe-DWCNTs/SPCEs) have been used as scaffolds for the preparation of ...electrochemical immunosensors for the simultaneous determination of the cytokines Interleukin-1β (IL-1β) and factor necrosis tumor α (TNF-α). IL-1β. Capture antibodies were immobilized onto HOOC-Phe-DWCNTs/SPCEs in an oriented form making using the commercial polymeric coating Mix&Go™. Sandwich type immunoassays with amperometric signal amplification through the use of poly-HRP-streptavidin conjugates and H2O2 as HRP substrate and hydroquinone as redox mediator were implemented. Upon optimization of the experimental variables affecting the immunosensor performance, the dual immunosensor allows ranges of linearity extending between 0.5 and 100 pg/mL and from 1 to 200 pg/mL for IL-1β and TNF-α, respectively, these ranges being adequate for the determination of the cytokines in clinical samples. The achieved limits of detection were 0.38 pg/mL (IL-1β) and 0.85 pg/mL (TNF-α). In addition, the dual immunosensor exhibits excellent reproducibility of the measurements, storage stability of the anti-IL-Phe-DWCNTs/SPCE and anti-TNF-Phe-DWCNTs/SPCE conjugates, and selectivity as well as negligible cross-talking. The dual immunosensor was applied to the simultaneous determination of IL-1β and TNF-α in human serum spiked at clinically relevant concentration levels and in real saliva samples.
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•Electrochemical immunosensor for simultaneous determination of IL-β1 and TNF-α cytokines.•Oriented immobilization of capture antibodies and signal amplification.•Improved analytical performance with respect to previous approaches and ELISA methods.•Application to human serum and saliva.
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