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History and Sources of Essential Oil Research
Published in K. Hüsnü Can Başer, Gerhard Buchbauer, Handbook of Essential Oils, 2020
The great majority of today's GC-MS applications utilize 1D capillary GC with quadrupole MS detection and electron ionization. Nevertheless, there are substantial numbers of applications using different types of mass spectrometers and ionization techniques. The proliferation of GC-MS applications is also a result of commercially available easy-to-handle dedicated mass spectral libraries (e.g., NIST/EPA/NIH 2005; WILEY Registry 2006; MassFinder 2007; and diverse printed versions such as Jennings and Shibamoto, 1980; Joulain and König, 1998; Adams, 1989, 1995, 2007 inclusive of retention indices) providing identification of the separated compounds. However, this type of identification has the potential of producing some unreliable results, if no additional information is used, since some compounds, for example, the sesquiterpene hydrocarbons α-cuprenene and β-himachalene, exhibit identical fragmentation pattern and only very small differences of their retention index values. This example demonstrates impressively that even a good library match and the additional use of retention data may lead in some cases to questionable results, and therefore require additional analytical data, for example, from NMR measurements.
Analysis Update—Full Spectrum Cannabis
Published in Betty Wedman-St Louis, Cannabis as Medicine, 2019
Robert Clifford, Scott Kuzdzal, Paul Winkler, Will Bankert
GC and HPLC have one thing in common with respect to detection: both instruments can utilize the very powerful mass spectrometer (MS). There are several types of mass spectrometers, but the most common are single quadrupole and triple quadrupole. Examples of single quadrupole mass spectrometers are GCMS and LCMS, while the triple quadrupole mass spectrometers are GC-MS/MS and LC-MS/MS (Figure 21.3). In situations where a single or triple quadrupole mass spectrometer could be used, the acronyms GCMS(/MS) or LCMS(/MS) may be used. A GC-MS/MS could be used in the single quadrupole GCMS mode for the analysis of terpenes. This is important because an analyst using a GC-MS/MS for contaminant testing of pesticides could also operate in the GCMS mode for terpene analysis. An LCMS(/MS) can be used to analyze amino acids and flavonoids. In the LC-MS/MS mode, the same instrument and detector could also measure contaminants like pesticides and mycotoxins/aflatoxins. Generally speaking, an MS(/MS) can replace all other detectors.
Emerging Biomedical Analysis
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
The detection of an ion in a modern mass spectrometer is achieved by creating an electric signal. The basic ion detector is the Faraday cup. The principle of the Faraday cup is that a current is induced when a packet of ions hits the dynode surface. The number and charge of ions are determined by measuring the current.
Use of omic technologies in early life gastrointestinal health and disease: from bench to bedside
Published in Expert Review of Proteomics, 2021
Lauren C Beck, Claire L Granger, Andrea C Masi, Christopher J Stewart
In this field, proteomics employs a variety of methodologies which over time, have built upon the conventional workflow. A typical proteomic workflow consists of sample collection and preparation, separation of proteins within samples and analysis by mass spectrometry (MS). Traditionally, separation of proteins within a sample is achieved by two-dimensional gel electrophoresis, whereby proteins are separated based on isoelectric point and molecular weight [51]. More recently, however, separation is often conducted using chromatography-based methods such as high-performance liquid chromatography (HPLC). Following separation, MS is used to measure the mass-to-charge ratio of proteins, and is therefore useful in determining the molecular weight of proteins [50]. Mass spectrometers generally consist of an ion source, a mass analyzer, and an ion current detector [42]. Combining the two analyzers allows for tandem MS, which is currently the preferred technique for proteomic analyses [42]. The most commonly used ionization methods for proteomic MS are electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI), although there are several variations on MS-based techniques [42,50]. Owning to extensively annotated databases, it is possible to identify the vast majority of peptides/proteins detected.
Considerations for mass spectrometry-based multi-omic analysis of clinical samples
Published in Expert Review of Proteomics, 2020
Esei T. Teclemariam, Melissa R. Pergande, Stephanie M. Cologna
The mass spectrometer plays a critical role for biomolecule analysis in clinical 'omic studies. The choice of mass spectrometer will depend on the needs of the user, specifically, dependent on whether experiments are targeted or untargeted in nature. High resolutionand mass accuracy instruments such as time-of-flight, orbitrap, and ion cyclotron resonance analyzers are commonly employed for untargeted/discovery-based applications. The added benefit of high resolution, mass accuracy, and tandem MS fragmentation spectral all assist with unknown analyte identification. This can be collected with compromises in speed that are found in other instrumentation platforms. For example, targeted MS analyses are primarily reliant on triple quadrupole mass spectrometers. Although these instruments are considered low mass resolution systems, they provide fast scan speeds, the ability to collected known m/z signals and reduce background signals. The added benefit of multiplexing capabilities has made triple quadrupoles very accessible for clinical analyses. Additionally, the speed, sensitivity, and resolution are important metrics to consider. Details of each specific technical component are beyond the scope of this discussion. Several reviews have been published outlining the role of MS in 'omic studies [88–93].
Proteomic investigations into hypertension: what’s new and how might it affect clinical practice?
Published in Expert Review of Proteomics, 2019
N. Corbacho-Alonso, E. Rodríguez-Sánchez, T. Martin-Rojas, L. Mouriño-Alvarez, T. Sastre-Oliva, G. Hernandez-Fernandez, L. R. Padial, L. M. Ruilope, G. Ruiz-Hurtado, M. G. Barderas
Against this background, the immunoassays that are currently in clinical use can analyze thousands of samples, but only for a few candidate biomarkers. As a targeted proteomics approach, SRM is commonly used to validate candidate biomarkers across large samples sets with high selectivity and sensitivity as compared with ELISA [57,58], and is a possible alternative to the classical methods based on immunodetection. The main clinical limitation of proteomics is obtaining a reproducible protein pattern in a suitable turnaround time. While mass spectrometry technology is much improved, there are practical considerations for its clinical application. Even so, -omics platforms are a required support for personalized medicine [59]. While many studies have been published with promising biomarkers of CV diseases and hypertension, few have been assessed in clinical trials. Further investigations are necessary and future directions for proteomics should include robust equipment for routine use. Moreover, efforts have been undertaken to improve data sharing in the scientific community and computational approaches have been developed to support the -omics data correlation. It should also be borne in mind that clinical staff will play an important role in the quality and improvement of research, for example, by establishing clinical characteristics for patient selection. This is extremely important since the subjects selected must present the same clinical characteristics and the same treatment. This will allow for good reproducibility to apply to an independent cohort of patients and with a larger number of samples.