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Sampling and Analysis Methodology for Semivolatile and Nonvolatile Organic Compounds in Air
Published in Richard B. Gammage, Stephen V. Kaye, Vivian A. Jacobs, Indoor Air and Human Health, 2018
Ralph M. Riggin, Bruce A. Petersen
PAHs are determined using either gas chromatography/mass spectrometry (GC/MS) or high performance liquid chromatography (HPLC) with fluorescence or ultraviolet (UV) absorption detectors. In general, the HPLC techniques are somewhat more sensitive than GC/MS, but the operating conditions must be carefully chosen for each compound. GC/MS can detect a wide range of compounds and generally gives adequate sensitivity, especially when multiple ion detection (MID) detection is employed. Consequently, HPLC is often employed when only one or two individual PAHs are of interest, with GC/MS being employed when a wide range of compounds are of interest. PAHs (quiñones, phenols) are very polar and can present problems in GC/MS analysis. Consequently, HPLC/fluorescence is used to a greater extent for these compounds. However, nitrosubstituted PAHs are not fluorescent and must be converted to the amine in order to be detected. Consequently, GC/MS is frequently the method of choice for nitro PAH. In this case, negative ion chemical ionization has proven to be extremely sensitive and selective, due to the electron withdrawing properties of the nitrosubstituent.
Detection Technology
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
Gas chromatography-mass spectrometry (GC-MS) instruments utilize, as the name suggests, a gas chromatograph in line with a mass spectrometer. The gas chromatograph separates molecules based on their volatility as they diffuse through a column of gas and information is obtained on the time it takes (retention time) for the individual components that make up the sample to migrate to the end of the gas column. As a separation technology, a gas chromatograph may be coupled to any number of detection instruments. It is included here as a common form of field detection technology.
Metabolomics
Published in Sanjeeva Srivastava, Multi-Pronged Omics Technologies to Understand COVID-19, 2022
Shalini Aggarwal, Nirjhar Banerjee, Shashwati Parihari, Jyotirmoy Roy, Kharanshu Bojak, Rhythm Shah
Recently, various analytical techniques have been evolved for metabolome profiling which includes FTIR, Raman spectroscopy, NMR spectroscopy, and MS (Figure 5.2b) (Segers et al. 2019; Mahmud and Garrett 2020; Instituto Tecnológico de Aguascalientes and Sánchez-Brito, 2020). Mass spectrometry is usually coupled with high-performance liquid chromatography (HPLC-MS) or gas chromatography (GC-MS) (Zeki et al. 2020). LC-MS is generally used to detect and identify medium polar to polar compounds, whereas GC-MS is mainly used to identify non-polar and volatile metabolites (Zeki et al. 2020). The separation of analytes depends on the column length, diameter, particle size, stationary phase, mobile phase, and column temperature. Column selection should be made based on the widest coverage for the screening of more number of unknown compounds which requires prior knowledge on the target analyte type (Gough, Bahaghighat, and Synovec 2019). The separation of analyte is mainly based on the hydrophobic and hydrophilic nature of the compound. C18 column and hydrophilic interaction liquid chromatography (HILIC) column are mainly used for the separation of hydrophobic compounds by reverse-phase (RP) and hydrophilic compounds, respectively (Schwaiger et al. 2019; Rampler et al. 2018). However, a mixed-mode column is now being used for the wide range coverage of both hydrophobic and hydrophilic metabolites. The selection of the mobile phase also plays a key role in the separation of metabolites (Maras et al. 2020; Shen et al. 2020). In RP chromatography, polar solvents (e.g., methanol, acetonitrile) are used as the mobile phase. Hydrophobic analytes are attached to the stationary phase and hydrophilic analytes pass with the mobile phase and elute first. Blank samples (i.e., all the organic solvents except biospecimen) are injected before the sample run to remove background compounds coming from organic solvents (Shen et al. 2020).
Efficient preparation of phosphazene chitosan derivatives and its applications for the adsorption of molybdenum from spent hydrodesulfurization catalyst
Published in Journal of Dispersion Science and Technology, 2022
Hala. A. Ibrahium, Bahig M. Atia, Nasser. S. Awwad, A. A. Nayl, Hend A. Radwan, Mohamed A. Gado
Gas chromatography with Mass spectrometer unit (GC/MS), also considered as an influential and powerful tool for the prediction of the molecular formula, purity and the more stable fragment [m/z]+. Some important fragmentation patterns, which are related to the synthesized PZEN chelating ligand, were observed such as [C6H6]˙ with a molecular weight of 78 (benzene ring), [C10H18]˙ with a molecular weight of 128 (naphthalene ring), [NH3]˙ with a molecular weight of 17, [C19H18N3PS]˙ with a molecular weight of 351 which represents the molecular ion peak of PZEN ligand, [P = N–O]˙ with a molecular weight of 63, [C18H15PN]˙ with a molecular weight of 276, [C18H15P]˙ with a molecular weight of 262 (triphenyl phosphene), [C6H7N]˙ with a molecular weight of 93 (aniline) and 76 molecular weight which express the formation of [CH4N2S, thiourea]˙ moiety. The whole analysis performed assures a satisfactory synthesis of TPPC chelating ligand. Specification of TPPC chelating ligand using GC/MS is illustrated in Figure 3(A).
In vitro abrasivity and chemical properties of charcoal-containing dentifrices
Published in Biomaterial Investigations in Dentistry, 2020
Foteini Machla, Aida Mulic, Ellen Bruzell, Håkon Valen, Ida Sofia Refsholt Stenhagen
The presence of naphthalene in NAO is unsurprising as naphthalene is reported as the most abundant PAH in biochar (product of pyrolysis used for agricultural and environmental applications rather than fuel) [34]. According to European Union regulation, the presence of naphthalene in cosmetic products is prohibited [35]. The toxicity of naphthalene is outlined in a report by the National Toxicology Program [36]. A limitation of the present study was that the presence of PAHs only was investigated in these charcoal-containing dentifrices. An alternative extraction protocol (Soxhlet extraction) or the use of liquid chromatography–mass spectrometry (LC-MS) rather than GC-MS may have revealed other PAHs [37]. LC-MS is normally capable of achieving lower limits of detection compared to GC-MS, depending on the molecular weight of the compound of interest. Elemental analysis of coconut-based charcoals used in waterpipes showed larger amounts of heavy metals (lead, zinc, iron, cadmium, aluminum, cobalt and chromium) compared to the content of cigarettes, therefore, the presence of other hazardous substances cannot be disregarded [38]. Furthermore, only one batch of each dentifrice was used and the country of origin of the charcoal was unknown. Thus, it is also reasonable to expect variation between batches or types of charcoal-based dentifrices [39].
Synthesis and characterisation of rubber seed oil trans-esterified biodiesel using cement clinker catalysts
Published in International Journal of Sustainable Energy, 2019
V. Aarathi, E. Harshita, Atira Nalinashan, Sidharrthh Ashok, R. Krishna Prasad
Gas chromatography–mass spectrometry (GC–MS) is an instrumental method used to find the different components of a sample. GC–MS is used for the separation of different compounds. The final composition of the biodiesel sample was analysed using a Thermo GC Trace Ultra version 5.0 Thermo MS DSQ II with a DB-5 MS Capillary Standard non-polar column with an internal diameter of 0.25 mm and a film thickness of 0.25 μm. The carrier gas used was Helium, with a flow rate of 1 ml/min. The temperature programming was set as 70°C and raised to 260°C at 6°C/min. Volume of sample injected was 1 μl. The GC image was obtained for CaO and cement clinker catalysts, and the mass spectroscopy image for the significant peaks was identified. The GC images for CaO and cement clinker catalyst are shown in Figures 14 and 15, respectively.