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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
LC-MS is highly sensitive and can identify a wide range of metabolites from each sample (Zheng et al. 2020; Doğan et al. 2020). MS1 is used for the quantification of the metabolites, and MS/MS is used for the identification of the metabolites. Generally, protonated analytes are detected in the positive ion mode, and deprotonated analytes are detected in the negative ion mode (Yuan et al. 2012). However, for metabolite quantification purposes, it requires more time than the NMR setup. 1H NMR (proton NMR) mainly provides compound quantification more precisely. The spectral peak obtained for one metabolite is proportional to the concentration of the metabolites in the sample. NMR also provides structural information about the metabolites (Snytnikova et al. 2019; Beckonert et al. 2007; Costa dos Santos Junior et al. 2020). However, NMR is less sensitive, and the total number of metabolites obtained from the NMR spectroscopy is very less in comparison to the metabolites obtained from LC-MS analysis. To eliminate false discoveries, it is critical to have multiple control runs (e.g., blank, standard mixtures) and quality control (QC) check steps (e.g., QC pools, internal standard) (Godzien et al. 2015).
Laboratory analysis of cyanobacterial toxins and bioassays
Published in Ingrid Chorus, Martin Welker, Toxic Cyanobacteria in Water, 2021
Linda A. Lawton, James S. Metcalf, Bojana Žegura, Ralf Junek, Martin Welker, Andrea Törökné, Luděk Bláha
The addition of a mass detector to chromatography systems makes a very powerful tool for the analysis of cyanotoxins. Mass spectra can provide an indication of the elemental composition and structure of an analyte along with determining the quantity of analytes for which reference materials are available with high sensitivity (see Box 14.2). A range of differing systems is available, and very careful consideration is required to determine which fulfils analytical requirements and is within the budget available. Different ion sources are available with positive electrospray ionisation (ESI) most commonly used in the analysis of cyanotoxins. The type of mass analyser (Caixach et al., 2017) also varies and can have a significant impact on cost and the data obtained; hence, it is essential that background evaluation is carried out to ensure the system suits the needs defined during planning (see section 14.1.1). In general, LC-MS will provide data relating to chromatographic retention times, the parent ion masses and fragmentation patterns for each compound as they are eluted. More complex LC-MS/MS systems combine a series of more than one mass detector (e.g., a triple quadrupole mass detector). As analyte ions pass through mass analysers, the former allow the selection of an analyte based on parent ion mass, while the latter allow the selective detection of fragment ions. This makes LC-MS/MS a highly specific analytical technique.
Nonionic Surfactants—Alkylphenols and Their Ethoxylates
Published in Pradyot Patnaik, Handbook of Environmental Analysis, 2017
These substances may be determined by LC/MS or GC/MS following their extractions from water, soil, and sediments. In addition, these compounds can be analyzed by HPLC-fluorescence, HPLC-UV, and GC-FID. Since such surfactants used commercially are mixtures of several oligomers and isomers, LC/MS is the preferred method of analyses. Several procedures are described in the literature. Most of these methods are based on LC/MS, while a few describe GC/MS or LC—fluorescence detection. Some of these analytical procedures are briefly outlined below. The LC/MS and GC/MS procedures are briefly discussed below. The LC/MS analysis involves reversed phase LC separation of the compounds followed by their mass spectrometric detection using either atmospheric chemical ionization or ESI. SPE procedures for isolation of compounds from aqueous samples are generally discussed in most works. Pressurized liquid extraction may be applied for solid samples. Ultrasonic solvent extractions or sonication methods are also equally suitable for soil, sediments, and other solid samples. Soxhlet and microwave-assisted extraction techniques may be applied too. Such extractions are usually followed by SPE cleanup steps before analysis.
Removal efficiency of dissolved organic matter from secondary effluent by coagulation-flocculation processes
Published in Journal of Environmental Science and Health, Part A, 2020
Natália Rodrigues Guimarães, Fabiane Dörr, Rodrigo de Oliveira Marques, Ernani Pinto, Sidney Seckler Ferreira Filho
Liquid chromatography-mass spectroscopy (LC-MS) has been the analytical instrumentation of choice for many compounds in complex matrices identification and quantification. Since it is impractical to evaluate all unknown compounds in wastewater samples, the choice of the monitoring species and parameters is dependent on the subject of the study. Besides its good versatility, selectivity, specificity, and sensitivity, LC-MS allows for the analysis of organic compounds with a wide range of polarities, solubilities, acid dissociation constants, partition coefficient, and stabilities under acidic and basic conditions. However, considering the complexity of wastewater samples, the matrix interference with the response of specific compounds might be a drawback of this technique to detect and quantify target analytes.[36]
Emerging contaminants in the atmosphere: Analysis, occurrence and future challenges
Published in Critical Reviews in Environmental Science and Technology, 2019
Pedro José Barroso, Juan Luis Santos, Julia Martín, Irene Aparicio, Esteban Alonso
MS is the detection method of choice due to its specificity and sensitivity and consequent unquestionable identification and quantification with very low limits of detection (LODs), and, to a lesser extent, electronic capture (ECD) (Shen et al., 2006), flame ionization (FID) (Thurén and Larsson, 1980), tandem mass spectrometry triple quadrupole (QqQ) (Wurl et al., 2006) and time of flight (TOF) (Barber et al., 2007). It is important to note that most methods require a derivatization step for the analysis of some of these compounds. Therefore, LC-MS/MS is presented as a convenient tool to reduce and simplify the experimental process, avoiding the loss of analytes. Other advantages of LC-MS/MS are sensitivity, selectivity, and the use of atmospheric pressure ionization techniques that allow soft ionization with little fragmentation of a wide range of compounds (Salgueiro-González et al., 2013).
Occurrence and seasonality of pharmaceutical compounds in urban wastewaters in two Portuguese regions
Published in Urban Water Journal, 2021
Catarina Silva, Cristina M. M. Almeida, João A. Rodrigues, Sofia Silva, Maria do Rosário Coelho, António Martins, Rita Lourinho, Eugénia Cardoso, Vítor Vale Cardoso, Maria João Benoliel, Maria João Rosa
Matrix effects play a relevant role on the LC-MS/MS analysis, hindering method sensitivity, linearity, precision and accuracy. Matrix effects, such as signals enhancement or suppression, may vary due to matrix complexity, potentially leading to the occurrence of different interferences. In order to evaluate these effects, wastewater samples were spiked and the obtained areas (AWW) were compared with those of injected standard at the same spiking level (AS), varying in the 102–630 µg/L range. The matrix effects were determined using the equation: enhancement/suppression (%) = [(AS-AWW)/AS] x 100.