China
Africa
Explore chapters and articles related to this topic
Determination of Pesticide Residues in Food of Animal Origin
Published in José L. Tadeo, Analysis of Pesticides in Food and Environmental Samples, 2019
Giulia Poma, Marina López-García, Roberto Romero González, Antonia Garrido, Adrian Covaci
The time-of-flight detector (TOF) has been applied in different matrices like fish [14] and honey, honeybee, and pollen [76] for the determination of multiple classes of pesticides. Both of them operated in the EI mode and employed a BPX-50 column [14] and a DB-XLB column [76]. On the other hand, to improve the drawbacks of the TOF detector, a hybrid system, consisting of a quadrupole/TOF (Q-TOF), has been applied for the determination of 50 pesticides in meat samples [34]. In this study, atmospheric pressure chemical ionization (APCI) has been used as an alternative to conventional ion sources applied in GC (EI or CI), minimizing the matrix effect observed in applying other ionization techniques. An overview of the recent literature for the application of GC coupled to TOF and Q-TOF in the determination of pesticides residues have been performed by Elbashir and Aboul-Enein (2017) [74].
Synthesis, Characterization, and Applications of Silica Nanomaterials from a Nanobiotechnological Perspective
Published in Pradipta Ranjan Rauta, Yugal Kishore Mohanta, Debasis Nayak, Nanotechnology in Biology and Medicine, 2019
Chityal Ganesh Kumar, Kanugala Sirisha, Puvvada Naga Prasad
Fourier Transform Infrared (FT-IR) spectroscopy allows probing of the surface silane chemistry of the synthesized silica nanoparticles by analyzing the surface functional groups and the associated chemical bond vibrations, such as the Si-O bond vibrations (1000–1200 cm–1), Si-OH bond vibrations (~940–960 cm–1), and Si-O bond vibrations (790–810 cm–1). Modification of the silica nanoparticle surface with amines, oxides, esters, and other functional groups leads to a shift in the wavenumbers. Dynamic light scattering analyzes the hydrodynamic diameter of silica nanoparticles in solution from the diffusion coefficients. The zeta potential of silica nanoparticles is the difference in potential between the layer of fluid in contact with the silica nanoparticle and the solution in which the nanoparticles are suspended. The ionic groups and the net charge of the silica nanoparticle surface play a significant role in determining the zeta potential of the dispersed nanoparticles. 29Si solid-state NMR (Nuclear Magnetic Resonance) spectroscopy enables the silica nanoforms to be subjected to magnetic fields and the magnetic field lines are passed. The nuclei get excited by the magnetic field lines, and a resonance is generated. Each intramolecular magnetic field inside a particular molecule exerts a specific resonance pattern. The XRD technique enables assessment of the purity and characterizes whether the nanomaterial has a crystalline nature. When X-rays hit the silica nanoparticles, they get diffracted with interference by following Bragg’s rule: 2d sin θ = nλ. X-ray photoelectron spectroscopy measures the electron binding energies of the silica nanoparticles. As the energy of incident X-rays are known, the measured kinetic energies of the sample electrons allow the measurement of the electron-binding energy of the sample. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a highly sensitive method for probing the surface composition of silica nanoparticles. The silica nanoparticles are hit by primary ion beams that sputter the nanoparticle surface to remove secondary ions from the surface, which are received by a time-of-flight detector, and the mass/charge ratio is represented in terms of m/z versus intensity.
Science and technology of a transformational multifunctional ultrananocrystalline diamond (UNCDTM) coating
Published in Functional Diamond, 2022
A key analysis of N-UNCD films was done using atomic scale resolution “Atom-Probe Analysis”, to determine if N atoms were inserted in the grain boundaries. N-UNCD films with the hypothesized N atoms inserted in the grain boundaries, were grown on atomically sharp tips. The tips were inserted in holder in an ultra-high vacuum system, where they were biased with a high positive potential with respect to a detector at ground potential, while picosecond laser pulses, impinging on the specimen’s microtip along the axis, triggered electric field-induced evaporation of ions from the surface of the N-UNCD-coated tip. The ions were accelerated along diverging electric field lines on the tips to project a highly magnified image of the microtip’s surface onto a position-sensitive time-of-flight detector. The time-of-flight of the ions was used to identify their mass-to-charge-state ratio and hence their chemical identities (see Figures 2, 3, and 4 in [31], for detailed explanation of the technique). 3 D-tomographic atom-probe tomography reconstructions of nano-diamonds provided information about the N and C atoms in the grain boundaries of N-UNCD films (see Figure 6 in [31], showing maps of single atoms distribution. These measurements provided key information confirming the presence of N atoms in the N-UNCD grain boundaries, supporting the modeling [30] and electrical measurements [27] indicating that the N atoms reacting with dangling C atoms bonds and releasing electrons for electrical conduction through the grain boundaries.
Can third-body stabilisation of bimolecular collision complexes in cold molecular clouds happen?
Published in Molecular Physics, 2022
Zhenghai Yang, Srinivas Doddipatla, Chao He, Shane J. Goettl, Ralf I. Kaiser, Ahren W. Jasper, Alexandre C. R. Gomes, Breno R. L. Galvão
Scattered species entering the detector were monitored via a triply differentially pumped quadrupole mass spectrometer (QMS) and ionised in an electron-impact ioniser (80 eV, 2 mA). The ions are then filtered according to mass-to-charge (m/z) ratio; ions that passed through the filter are collected by a Daly-type time-of-flight detector. The detection region is housed in a triply differentially pumped, rotatable ultrahigh vacuum chamber at typical pressures of 6 × 10−12 Torr. The TOF spectra collected at different angles were integrated and normalised with respect to the intensity at the CM angle to extract the laboratory angular distribution at a specific m/z ratio. To obtain information on the chemical dynamics, the laboratory data were transformed into the CM reference frame using a forward-convolution routine [31]. The user-defined angular T(θ) and translational energy P(ET) flux distribution are varied iteratively until a best fit of the laboratory TOF spectra and angular distribution is reached.
Enhanced marine monitoring and toxicity study of oil spill dispersants including Corexit EC9500A in the presence of diluted bitumen
Published in Journal of Environmental Science and Health, Part A, 2020
Pamela Brunswick, Ceara Y. MacInnis, Jeffrey Yan, Craig Buday, Ben Fieldhouse, Carl E. Brown, Graham van Aggelen, Dayue Shang
Liquid chromatography quadrupole time-of-flight mass spectrometry analysis (LC/QToF) was performed using an Agilent Infinity 1290 liquid chromatograph system (LC) with Infinity 1260 autosampler, and an Agilent 6550 iFunnel quadrupole mass spectrometer with time-of-flight detector (QToF) controlled by MassHunter software.