Search results for "pole [approximation]"
showing 10 items of 522 documents
Comparison of liquid chromatography using triple quadrupole and quadrupole ion trap mass analyzers to determine pesticide residues in oranges.
2005
Liquid chromatography-triple quadrupole/mass spectrometry (LC-TQ/MS) and liquid chromatography-quadrupole ion trap/mass spectrometry (LC-QIT/MS) for determining bupirimate, hexaflumuron, tebufenpyrad, buprofezin, pyriproxyfen, and fluvalinate in fruits have been compared. The differences in the mass spectra obtained by triple and ion trap quadrupoles are discussed, showing how both of them provide interesting features. The evaluation of the two instruments was carried out by ethyl acetate extraction of oranges spiked with the studied pesticides at LOQ and 10 times the LOQ. Results obtained by LC-TQ/MS correlated well with those obtained by LC-QIT/MS. Recoveries were 70-94% by LC-TQ/MS and 7…
Capabilities of different liquid chromatography tandem mass spectrometry systems in determining pesticide residues in food
2007
Abstract Three different liquid chromatography–mass spectrometry (LC–MS) instruments equipped with triple quadrupole (QqQ), quadrupole ion trap (QIT) and quadrupole-time-of-flight (QqTOF), suitable to carry out tandem mass spectrometry, were examined to determine pesticide residues in food. Twelve pesticides (acrinathrin, bupirimate, buprofezin, cyproconazole, λ-cyhalothrin, fluvalinate, hexaflumuron, kresoxim-methyl, propanil, pyrifenox, pyriproxyfen and tebufenpyrad) and six matrices (oranges, strawberries, cherries, peaches, apricots and pears) were taken as model. The comparison was focused on two aspects: the quantitative, covering sensitivity, precision and accuracy as well as the qua…
Investigations of Chl a aggregates cross-linked by dioxane in 3-methylpentane
1997
In this work, dioxane-bound aggregates of chlorophyll a are prepared in 3-methylpentane. The properties of the aggregates are studied by using steady-state and time-resolved spectroscopies. The Q -region absorption spectrum of the y chlorophyll a-dioxane aggregate shows four clearly resolvable narrow bands with comparable intensities. The band maxima are located at 683, 689, 698 and 702 nm. The emission spectrum consists of two emission bands centred at 699 and 702 nm suggesting the presence of two types of aggregates. High degree of fluorescence polarization is detected yielding the angles between the absorption transition moments with respect to the 702 nm emission transition moment. The …
The application of phospholipid removal columns and ultra-high performance liquid chromatography-tandem quadrupole mass spectrometry for quantificati…
2016
In this study a robust and sensitive method based on a proposed sample purification procedure, using zirconia-coated Phree™ columns and analysis by ultra-high performance liquid chromatography with triple quadrupole tandem mass spectrometry are presented for the assessment of multi-class antibiotics in farmed fish species. The sample preparation procedure benefited from combined precipitation of proteins and selective removal of phospholipids by Phree™ columns, resulting in a high sensitivity of the method (LOQ 0.3-9mgkg(-1)). The in-house validation results (precision, repeatability, decision limit CCα, detection capability CCβ, etc.) indicate that the elaborated method is fully suitable f…
Una inaspettata biodiversità valutata con la trappola malaise: il caso dei collemboli di Lampedusa
2013
All‟interno di uno studio sulla biodiversità dell‟entomofauna dell‟Isola di Lampedusa, che verteva principalmente sulla fauna aerea, si sono trovati diversi taxa normalmente appartenenti alla fauna edafica. Infatti per il monitoraggio sono state utilizzate trappole di tipo Malaise internazionalmente impiegate e consigliate nei protocolli per il monitoraggio di popolazioni di insetti volatori. Inaspettatamente, anche se qualche altro caso è citato in letteratura, si sono rinvenuti diversi taxa più tipicamente rappresentativi della fauna del suolo ed in particolare dell‟epifauna quali chilopodi, collemboli, coleotteri carabidi. La nostra attenzione si è focalizzata sui collemboli in quanto so…
An automatic L1-based regularization method for the analysis of FFC dispersion profiles with quadrupolar peaks
2023
Fast Field-Cycling Nuclear Magnetic Resonance relaxometry is a non-destructive technique to investigate molecular dynamics and structure of systems having a wide range of ap- plications such as environment, biology, and food. Besides a considerable amount of liter- ature about modeling and application of such technique in specific areas, an algorithmic approach to the related parameter identification problem is still lacking. We believe that a robust algorithmic approach will allow a unified treatment of different samples in several application areas. In this paper, we model the parameters identification problem as a con- strained L 1 -regularized non-linear least squares problem. Following…
GROMEX: A Scalable and Versatile Fast Multipole Method for Biomolecular Simulation
2020
Atomistic simulations of large biomolecular systems with chemical variability such as constant pH dynamic protonation offer multiple challenges in high performance computing. One of them is the correct treatment of the involved electrostatics in an efficient and highly scalable way. Here we review and assess two of the main building blocks that will permit such simulations: (1) An electrostatics library based on the Fast Multipole Method (FMM) that treats local alternative charge distributions with minimal overhead, and (2) A $λ$-dynamics module working in tandem with the FMM that enables various types of chemical transitions during the simulation. Our $λ$-dynamics and FMM implementations d…
Mass Spectrometry in Food Quality and Safety
2015
Abstract In recent years, mass spectrometry has gained a wide recognition as a selective and fast technique for the analysis and assessment of a wide range of food products. The state of the art in the determination of safety and quality of food is presented to illustrate the capability of this technique for classification and grading, defect and disease detection, distribution and visualization of chemical attributes, and evaluations of overall quality of meat, fish, fruits, vegetables, and other food products. The features of mass spectrometry for each category were summarized in the aspects of the investigated quality and safety attributes, the used systems (triple quadrupole, quadrupole…
Instabilities of ion motion in a linear Paul trap
2006
Abstract We have investigated the stability properties of a linear radio frequency ion trap with cylindrical electrodes. Inside the region of stability for an ideal trap we found a number of instabilities similar to those experimentally observed in three-dimensional traps. They arise from higher order contributions to the ideal quadrupole trapping potential. The static potential for axial confinement shifts the radial ion oscillation frequencies and leads to additional instabilities.
Antiproton confinement in a Penning-Ioffe trap for antihydrogen.
2007
Antiprotons ((p) over bar) remain confined in a Penning trap, in sufficient numbers to form antihydrogen ((H) over bar) atoms via charge exchange, when the radial field of a quadrupole Ioffe trap is added. This first demonstration with (p) over bar suggests that quadrupole Ioffe traps can be superimposed upon (p) over bar and e(+) traps to attempt the capture of (H) over bar atoms as they form, contrary to conclusions of previous analyses.