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Analysis of Pesticide Residues by Chromatographic Techniques Coupled with Mass Spectrometry
Published in José L. Tadeo, Analysis of Pesticides in Food and Environmental Samples, 2019
Wan Jing, Jin Maojun, Jae-Han Shim, A.M. Abd El-Aty
The triple quadrupole is a mass analyzer composed of three sets of quadrupoles. The first and third sets of quadrupoles are mass analyzers, and the middle set of quadrupoles is a collision activation chamber. It has several scanning modes, including product ion mode, precursor ion mode (also known as parent ion mode), neutral loss mode, and multiple reaction monitoring (MRM). The first three scanning modes are mainly used for the structural analysis of compounds by studying the fragmentation pathway of ions and the attribution of each ion. The MRM model is mainly used for quantitative analysis. It has better selectivity, stronger interference rejection ability, and a lower detection limit than the SIM model of the single quadrupole mass analyzer. The triple quadrupole mass spectrometer is commonly used in GC–MS/MS and LC–MS/MS. It is useful for the study of organic structure, and can also be used for the direct identification of mixed organics. It has a wide range of applications in pesticide multi-residue analysis.
Mass Spectrometry Instrumentation
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Yuan Su, Li-Rong Yu, Thomas P. Conrads, Timothy D. Veenstra
The quadrupole mass spectrometer has historically been the most commonly used mass analyzer in combination with ESI (Yost and Boyd, 1990). A quadrupole mass analyzer consists of four metal rods arranged in parallel, to which direct current (DC) and radio frequency (RF) voltages are applied. Ions with different mass-to-charge ratios are separated based on the differences in the stability of their trajectory in the oscillating electric field (Figure 14.9a). When accelerated ions enter the quadrupole, they are drawn towards two electric rods with the opposite charge to the ions. Since the sign of the potential on the rods changes with time, the running direction of the ions changes, and their running trajectory can be controlled by adjusting the oscillating electric field. As a result, only ions with the selected m/z values can be focused in the center of the field and safely pass through the quadrupole.
Gas Chromatography–Mass Spectrometry
Published in Leo M. L. Nollet, Dimitra A. Lambropoulou, Chromatographic Analysis of the Environment, 2017
The single quadrupole mass analyzer consists of four parallel rods of circular cross section that are connected in pairs and a combination of radio frequency and direct current voltage is applied between the rods. Ions will travel down the quadrupole between the rods, and for a given ratio of voltages, some will reach the detector, while others will collide with the rods and will not reach the detector (Hird, 2008). This process is called mass filtering, and it is wholly dependent on the voltage applied. A single quadrupole mass analyzer can be operated in either full-scan or selected ion-monitoring (SIM) mode. In full-scan mode, a wide range of ions is monitored, and this mode is particularly useful for identifying the components of a compound by using a mass spectrum. The latter, as its name suggests, monitors ions of a limited mass range, thus offering better sensitivity because monitoring of only a few ions takes place, thus increasing the acquisition time but compromising on the quality of the mass spectra (Hajslova and Cajka, 2007). However, in previous years this mode had the disadvantage of being complicated and difficult to maintain when the list of target analytes was increased. Instrument vendors such as Agilent have since solved this problem by use of the retention time locking (Almeida et al., 2007). For this reason, many publications have reported on its use for quantitation purposes of different environmental pollutants such as PPCPs (Bisceglia et al., 2010), PBDEs (Gorga et al., 2013), PCBs (Zhou et al., 2010), and polycyclic aromatic hydrocarbons and pesticides (Borras et al., 2011; Merdassa et al., 2013; Tankiewicz et al., 2013), among others. Table 1.3 summarizes some of the applications of GC-MS in environmental analysis.
High-resolution spectroscopy of the ν3 antisymmetric C–H stretch of C2H2 + using leak-out action spectroscopy
Published in Molecular Physics, 2023
Stephan Schlemmer, Eline Plaar, Divita Gupta, Weslley G. D. P. Silva, Thomas Salomon, Oskar Asvany
The rovibrational transitions of were measured in COLTRAP, a 4 K 22-pole ion trap instrument which has been described in detail previously [17,18]. Ions were generated in a storage ion source by electron impact ionisation ( eV) of a 50:50 acetylene (; purity) – helium ( purity) gas mixture. The initially produced ions are pulsed into a quadrupole mass analyzer and selected for mass m = 26 u. The remaining ions (on the order of several ten thousands) are guided into a 22-pole ion trap mounted on a 4 K cold head. Efficient trapping and thermalisation of the ions is achieved through collisions with helium buffer gas which is continuously introduced at low densities. Additionally, in order to provide a proper collisional partner for the novel LOS approach and to avoid extensive freeze-out at the trap surfaces, a 1:3 mixture of neon diluted in helium is pulsed into the trap through a piezoelectrically actuated valve at the beginning of each trapping cycle.
Incubation media modify silver nanoparticle toxicity for whitefish (Coregonus lavaretus) and roach (Rutilus rutilus) embryos
Published in Journal of Toxicology and Environmental Health, Part A, 2022
Roland Vogt, Benedikt Steinhoff, Darya Mozhayeva, Eva Vogt, George Metreveli, Holger Schönherr, Carsten Engelhard, Josef Wanzenböck, Dunja Katharina Lamatsch
The size of AgNPs in suspensions was assessed also via spICP-MS. Here, 2 mL aliquots were collected from five wells (= 10 mL, n = 1), frozen using liquid nitrogen and stored at −20°C using polypropylene cryo vials. A model iCAP Qc (Thermo Fisher Scientific, Bremen, Germany) ICP-MS instrument with a single quadrupole mass analyzer was used for spICP-MS measurements. In short, the data acquisition for spICP-MS was performed with a prototype DAQ (continuous 5 µs time resolution; Strenge and Engelhard 2016). After careful optimization (Mozhayeva and Engelhard 2017; Mozhayeva, Strenge, and Engelhard 2017), particle characterization was performed on a particle-by-particle level with a particle size LOD of 10.5 nm in the medium samples. Particle number LOD was set to 10 particles per measurement, according to Poisson statistics with false positives and false negatives probability set to 5% (Currie 1972). Data processing was performed by extracting nanoparticle ion cloud events from the raw data, as described by Strenge and Engelhard (2016). Before spICP-MS measurement, water samples were thawed in the fridge at 4°C overnight. Prior to the analysis, samples were allowed to reach room temperature and shaken for 15 min. The samples were diluted with double distilled water immediately before spICP-MS measurements. The size calibration was done with 20, 40, and 60 nm citrate-coated AgNPs (Nanocomposix, San Diego, CA, USA) with the sizes taken from the specification sheets from the manufacturer´s TEM data. The experimental conditions are presented in Table A 4.
Combined crossed molecular beams and computational study on the N(2D) + HCCCN(X1Σ+) reaction and implications for extra-terrestrial environments
Published in Molecular Physics, 2022
Pengxiao Liang, Luca Mancini, Demian Marchione, Gianmarco Vanuzzo, Francesco Ferlin, Pedro Recio, Yuxin Tan, Giacomo Pannacci, Luigi Vaccaro, Marzio Rosi, Piergiorgio Casavecchia, Nadia Balucani
The experiments were carried out using a crossed molecular beam apparatus coupled with a quadrupole mass spectrometer and time-of-flight (TOF) analysis. The experimental approach has been described in detail elsewhere [44–46], and only a brief description is given here. Two supersonic beams were crossed at an intersection angle (γ) of 90°in the scattering chamber. During the experiment, the pressure was maintained at about 7×10−5 Pa to ensure single-collision conditions. Product angular and velocity distributions were measured by an electron impact ioniser followed by a quadrupole mass analyzer and a Daly ion detector contained in a triply differentially pumped ultrahigh vacuum (UHV) chamber which can be rotated in the collision plane around the intersection axis of the two beams.