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Determination of Pesticides in Water
Published in José L. Tadeo, Analysis of Pesticides in Food and Environmental Samples, 2019
Rosa Ana Pérez, Beatriz Albero, José L. Tadeo
Time of flight mass spectrometry (TOF-MS) is the result of the significant advances undergone in analytical instrumentation. Thus, GC, LC, or comprehensive two-dimensional gas chromatography (GC×GC) coupled to TOF-MS have been used in the multiresidue analysis of a broad number of pesticides in water. Hernandez et al. [83] reported that TOF-MS hyphenated to LC and GC allows large screening of many organic pollutants in surface water and soil samples. Whereas, Ferrer and Thurman [33] reported a multiresidue method for the chromatographic separation and accurate mass identification of 101 pesticides and their degradation products using LC–TOF-MS and Matamoros et al. [84] reported an analytical procedure based on GC×GC coupled with TOF-MS for the simultaneous determination of 97 organic contaminants, many of them pesticides, at trace concentration in river water.
Genotoxicity of quinone: An insight on DNA adducts and its LC-MS-based detection
Published in Critical Reviews in Environmental Science and Technology, 2022
Yue Xiong, Han Yeong Kaw, Lizhong Zhu, Wei Wang
Time of flight mass spectrometry (TOF-MS) has an ion drift tube, where ions of different masses can be separated according to the m/z value. The high-resolution property of quadrupole TOF (QTOF) can be used for the effective screening, detection and further validation of exact molecular mass for DNA adducts. By using the UPLC(C18)-ESI-QTOF-MS analytical system, the clear peaks of 7 DNA adducts (4-Hydroxy-1-(3-pyridyl)-1-butanone, N3-(2-carbamoyl-2-hydroxyethyl)ade, N7-(2-Carbamoyl-2-hydroxyethyl)gua, N2-Ethyl-2′-dA, O6-Methyl-2′-dG, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, 4-oxo-4-(3-pyridyl)butanoic acid) were simultaneously screened from circulating extracellular DNA (cDNA) in human blood samples, and their detailed molecular masses were successfully identified (Dementeva et al., 2016).
Evolution of the light-absorption properties of combustion brown carbon aerosols following reaction with nitrate radicals
Published in Aerosol Science and Technology, 2020
Zezhen Cheng, Khairallah M. Atwi, Zhenhong Yu, Anita Avery, Edward C. Fortner, Leah Williams, Francesca Majluf, Jordan E. Krechmer, Andrew T. Lambe, Rawad Saleh
Volatile organic compounds (VOCs) and oxygenated VOCs (OVOCs) were measured using a Vocus Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-MS, Tofwerk AG/Aerodyne Research, Inc.) (Krechmer et al. 2018) with H3O+ reagent ion. PTR-MS data were analyzed using the Tofware software package (Tofwerk AG, Aerodyne Research, Inc.) implemented in IGOR Pro (Wavemetrics, Inc.). Ensemble mass spectra of the particles and their aerodynamic size distributions were measured with two Aerodyne time-of-flight aerosol mass spectrometers (AMS). One AMS was operated with the standard tungsten vaporizer configuration to enable detection of non-refractory aerosol components with flash vaporization at 600 °C followed by electron impact ionization and time-of-flight mass spectrometry (e.g., DeCarlo et al. 2006). This AMS was equipped with a long high-resolution (resolving power up to ∼8,000 Δm/m) time-of-flight mass spectrometer L-ToF-AMS. The other AMS, a soot particle aerosol mass spectrometer (SP-AMS), was operated with a λ = 1064 nm laser vaporizer to enable detection of aerosol components that absorb at 1064 nm as well as species internally mixed with the absorbing aerosols (Onasch et al. 2012). The tungsten vaporizer was removed so that only absorbing particles were detected. This AMS used a high resolution TOFMS with resolving power up to ∼4,000 Δm/m. Elemental analysis yielding O/C, H/C, and N/C ratios was performed on AMS measurements using the SQUIRREL/PIKA software package implemented in IGOR Pro (Aiken, Decarlo, and Jimenez 2007; Canagaratna et al. 2015). To calculate N/C, we assumed that AMS signals at m/z = 30 (NO+) and m/z = 46 (NO2+) were associated with PAH + NO3 oxidation products (details in Section 3.2.1) and therefore were classified as organics in the software.
Characterisation of the b 3Σ+, v = 0 state and its interaction with the A 1Π state in aluminium monofluoride
Published in Molecular Physics, 2021
M. Doppelbauer, N. Walter, S. Hofsäss, S. Marx, H. C. Schewe, S. Kray, J. Pérez-Ríos, B. G. Sartakov, S. Truppe, G. Meijer
Figure 1(a) shows the energy level diagram of the electronic states relevant to this study, together with a rotationally resolved spectrum of the band in 1(b), and a sketch of the experimental setup in 1(c), which is similar to the one reported previously [3]. The molecules are produced by laser-ablating an aluminium rod in a supersonic expansion of 2% SF seeded in Ne. After passing through a skimmer, the ground-state molecules are optically pumped to the metastable state by a frequency-doubled pulsed dye laser using the Q-branch of the band. For this, 367 nm radiation with a bandwidth of 0.1 cm and pulse energy of 6 mJ in a beam with a waist radius of about 2 mm is used. The Q-branch of this transition falls within this bandwidth. Therefore, many rotational levels in the metastable state are populated simultaneously. Via the Q-branch, only the f-levels in are populated. Alternatively, if the molecules are optically pumped to the metastable state using spectrally isolated R or P lines, only the e-levels are populated. Further downstream, at z = 55 cm from the source, the molecular beam is intersected with light from a second pulsed dye laser tuned to the transition near 569 nm. For pulse energies exceeding 6 mJ (unfocused, with an waist radius of about 5 mm), this laser transfers population to the state and subsequently ionises the molecules by having them absorb two more photons from the same laser. Such a one-colour (1 + 2)-REMPI scheme using an unfocused laser beam is very uncommon. However, AlF has numerous electronically excited states that lie one photon-energy above the b state energy, strongly enhancing the non-resonant two-photon ionisation probability. The ions are mass-selected in a short time-of-flight mass spectrometer (TOF-MS) and detected using micro-channel plates. The TOF-MS voltages are switched on shortly after the ionisation laser fires; this way ionisation occurs under field-free conditions and the states have a well-defined parity. The (1 + 2)-REMPI scheme uses low-energy photons and an unfocused laser beam, which has the benefit of producing a mass spectrum with only a single peak, corresponding to AlF. The spectrum, displayed in Figure 1(b), shows the ion signal as a function of the REMPI laser frequency. The spectral lines are labelled by , where , as the quantum number J is not well-defined in the b state, vide infra. Since only the f-levels of the state are populated, the spectrum consists of , i.e. O, Q and S branches.