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Supercritical Fluid Chromatography Instrumentation
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Thomas L. Chester, J. David Pinkston
As the name implies, atmospheric pressure photoionization (APPI) uses ultraviolet photons to ionize analytes [130]. The wavelength of the UV radiation is chosen to exceed the ionization potentials of the analytes but not to exceed the ionization potentials of CO2 and common SFC modifiers. APPI can provide unique advantages in some applications of SFC/MS as compared with APCI or ESI. SFC has often been used for the separation of lipophilic mixtures. Many lipophilic, non-surface-active molecules do not ionize particularly well in ESI, in comparison to more surface-active molecules. But APPI often works well with these lipophilic molecules, so it is well suited for the separation of lipophilic mixtures by SFC/MS.
Polycyclic aromatic hydrocarbons (PAHs): Updated aspects of their determination, kinetics in the human body, and toxicity
Published in Journal of Toxicology and Environmental Health, Part B, 2023
Fernando Barbosa, Bruno A. Rocha, Marília C. O. Souza, Mariana Z. Bocato, Lara F. Azevedo, Joseph A. Adeyemi, Anthony Santana, Andres D. Campiglia
LC-MS/MS methods have also been developed for quantifying PAHs (Avagyan et al. 2015; Cai et al. 2009; Lien, Chen, and Wu 2007; Lung and Liu 2015; Raponi et al. 2017; Wang et al. 2017; Wolkenstein 2019). Liquid chromatography is required when molecules are not easily volatilized and when it is necessary to simultaneously quantify polar- and nonpolar molecules. In addition, LC-MS presents a reliable alternative for HMW PAH quantification when fluorescence detection is not possiblePlaza-Bolaños, Frenich, and Martínez Vidal (2010). HPLC is a reliable method for separating isomers due to the use of specific columns and organic additives; however, quantifying these compounds by sequential mass spectrometry is difficult due to the PAH structure, which is minimally ionized under mild ionization sources such as electrospray (ESI). Further, ESI is incompatible with the normal phase using flammable organic solvents such as hexane because there is a risk of explosion despite these solvents offering the best degree of solubility for these PAHs (Cai et al. 2009). Therefore, other ionization sources need to be used, such as atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) (Lien, Chen, and Wu 2007; Lung and Liu 2015; Wolkenstein 2019). PAH analysis by LC-MS/MS is not common in research labs, and these methods are scarce in the literature.
Transformation of asphaltenes of vacuum residues in thermal and thermocatalytic processes
Published in Petroleum Science and Technology, 2022
Akim S. Akimov, Nikita N. Sviridenko
For a long time, the study of the properties of asphaltenes (determination of the molecular mass, particle size, structure, and morphology) has been an extremely difficult task. First of all, this was due to their tendency to agglomeration. However, an analysis of publications over the past 15–20 years has shown obvious progress in studying the properties of asphaltenes (Ganeeva, Yusupova, and Romanov 2011; Schuler et al. 2015; Rogel and Witt 2017; Chen et al. 2018). For example, it has been found out using new mass spectrometric methods of analysis such as Laser Desorption Ionization-Mass Spectrometry (LDI-MS), Atmospheric Pressure Photoionization-Mass Spectrometry (APPI-MS), Field Ionization-Mass Spectrometry (FI-MS), Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS), and Field Desorption and Field Ionization Mass Spectrometry (FD-FI-MS) that the molecular mass of asphaltenes varies within the range 300–1400 g·mol−1. Summary of results of measurement of molecular diffusion by various methods revealed that the size of the asphaltene molecule was in the range from 1.2 to 2.4 nm. The methods used were as follows: fluorescence correlation spectroscopy (FCS), time-resolved fluorescence depolarization (TRFD), 1H diffusion ordered spectroscopy magnetic resonance (1H DOSY NMR), high resolution transmission electron microscopy (HRTEM), small angle X-ray scattering (SAXS), and X-ray Raman spectroscopy (XRRS).
Firefighter hood contamination: Efficiency of laundering to remove PAHs and FRs
Published in Journal of Occupational and Environmental Hygiene, 2019
Alexander C. Mayer, Kenneth W. Fent, Stephen Bertke, Gavin P. Horn, Denise L. Smith, Steve Kerber, Mark J. La Guardia
One fabric sample from each hood was analyzed for 15 PAHs using NIOSH Method 5506 (modified for bulk material analysis).[25] The other fabric sample was analyzed using ultra-performance liquid chromatography (UPLC) – atmospheric pressure photoionization (APPI) tandem mass spectrometry as previously described by La Guardia et al.[26] for the following compounds. Polybrominated diphenyl ethers (PBDEs): 2,2’,4,4’-tetra-bromodiphenyl ether (BDE) (BDE-47), 2,2’,3,4,4’,-penta-BDE (BDE-85), 2,2’,4,4’,5-penta-BDE (BDE-99), 2,2’,4,4’,6-penta-BDE (BDE-100), 2,2’,4,4’,5,5’-hexa-BDE (BDE-153), 2,2’,4,4’,5,6’-hexa-BDE (BDE-154), 2,2’,3,4,4’,5,6-hepta-BDE (BDE-183), and deca-BDE (BDE-209) .Non-PBDE flame retardants (NPBFRs): 1,2-bis (2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenylethane (DBDPE), 2-ethylhexyl 2,3,4, 5-tetrabromobenzoate (TBB), di (2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), hexabromocyclododecane (α-, β-, γ-HBCD), and tetrabromobisphenol-A (TBBPA).Organophosphate flame retardants (OPFRs): tris (2-chloroethyl) phosphate (TCEP), tris (1-chloro-2-propyl) phosphate (TCPP) and tris (1,3-dichloro-2-propyl) phosphate (TDCPP)) and non-halogenated organophosphate flame retardants (non-HOPFRs): tricresyl phosphate (TCP) and triphenyl phosphate (TPP).