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![a) Chemical ionization [6]. b) Atmospheric Pressure Chemical ionization Source by Waters UK.](profile/Sharad-Medhe/publication/326264792/figure/fig2/AS:646378468438017@1531120044728/a-Chemical-ionization-6-b-Atmospheric-Pressure-Chemical-ionization-Source-by-Waters.png)
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![Figure 2: a) Chemical ionization [6]. b) Atmospheric Pressure Chemical...](profile/Sharad-Medhe/publication/326264792/figure/fig2/AS:646378468438017@1531120044728/a-Chemical-ionization-6-b-Atmospheric-Pressure-Chemical-ionization-Source-by-Waters_Q320.jpg)
Mass Spectrometry- It is an analytical technique that generates charged particles in the form of ions from the
substance to be analysed to measure its mass to charge ratio. Ion Source plays an important role for generation of
charged ions which further travels through analyser and ends at detector. The production of intact molecular ions
can be ach...
Contexts in source publication
Context 1
... Electron Impact thermally volatile and stable compounds of mass range 500 Da are introduced. A beam of electron at a pressure of greater than 10-3 Torr passes through a gas phase sample and collides with neutral analyte molecules (M) which produces charged ion or a fragment ion. 70 eV electron energy is required to form fragment ions. By collecting positive ions in focusing plates they are passed to mass analyzer ( Figure 1). Although EI has some limitation, EI causes extensive fragmentation so that the molecular ion is not observed for many compounds. Chemical ionization: Chemical ionization (CI) is a soft ionization technique which is useful when no molecular ion is observed in Electron Impact mass spectrum. Burnaby Munson and Frank H Field in 1966 [5] introduced chemical ionization for first time. The regular difference of this technique is Charge-exchange chemical ionization and atmospheric-pressure chemical ionization (APCI). Comparatively lower energy requires to this process than Electron Ionizations. Sometimes a lower energy corresponds to no fragmentation and or usually a simpler spectrum. As softer ionization technique it gives less fragmentation and easier to find molecular ions (Figure ...
Context 2
... gas is directly releases in to ionization chamber and electrons from filament ionize the reagent gas. Oxygen and hydrogen are used in negative ion chemical ionization [7]. In APCI the charged ions are generated using voltage 2 to 4 KV by using corona discharge needle. Wherein chemical ionization it is produced by applying 70 eV through filament (Figure 2b). There is a disadvantage for this technique. As there is no fragmentation it is less ...
Citations
... Chromatographic separation under positive and negative electrospray modes is a crucial step in mass spectrometry to create ions and expand the range of detectable micropollutants (Medhe, 2018). Positive electrospray mode is commonly used for compounds that readily lose electrons, while negative electrospray mode is often used for compounds with a high electron affinity (Medhe, 2018). ...
... Chromatographic separation under positive and negative electrospray modes is a crucial step in mass spectrometry to create ions and expand the range of detectable micropollutants (Medhe, 2018). Positive electrospray mode is commonly used for compounds that readily lose electrons, while negative electrospray mode is often used for compounds with a high electron affinity (Medhe, 2018). For micropollutants in positive ionization electrospray mode, the percentage of methanol linearly increased from 0 % to 100 % for 5 min and was maintained at 100 % for 3 min. ...
... By injecting small amounts of solid or liquid materials such as polymers, proteins, and lipids in plasma via spraying, vaporization, ablation [1], or sputtering [2], the variety of sample types that can be analyzed using this method increases tremendously. Mass spectrometers are used in analytical systems in combination with a large range of ionization methods [3,4] (such as discharges, ions bombardment of surfaces in secondary ion mass spectrometry (SIMS), photoionization, electrospray ionization, and matrix-assisted laser desorption ionization (MALDI)). Therefore, nowadays, mass spectrometry is used intensively not only in chemistry and physics research [5] but also for applications in material [6] and environmental sciences [7], and in proteomics [8], metabolomics, or pharmaceutical fields [9]. ...
In this work, we describe an ion mass spectra processing method from plasmas generated in Ar and Ar/H2 gases in contact with tungsten surfaces. For this purpose, advanced model functions, i.e., those suitable for fitting the experimental mass peak profiles, are used. In addition, the peak positions, peak shapes, abundances, and ion ratios are the parameters considered for building these functions. In the case of a multielement magnetron target, the calibration of the mass spectra with respect to the peak shape and position on the m/z scale is helpful in reducing the number of free variables during fitting. The mass spectra fitting procedure is validated by the obtained isotopic abundances of W ions in W/Ar magnetron plasmas, which, in turn, are comparable with their natural abundance. Moreover, its usefulness is exemplified by calculating the ratio of WH+/W+ ions in W/Ar/H2 plasma. This work paves the way for obtaining relevant results regarding ion species in plasma even in the case of using general-purpose mass spectrometers with limited resolution and accuracy. Although this method is illustrated for the W/Ar/H2 plasma system, it can be easily extendable to any plasma type.
... Sample is expelled constantly from the capillary end which leads to the formation of the Taylor cone, a distorted capillary outflow where a fine mist of charged components is emitted by the aid of nebulizing gas (N 2 ). The resultant droplets undergo desolvation and Coulomb fission until the droplets acquire the extra charge and transform into gas phase ions[12,43,44]. Ions freed from the solvent travel to the mass analyzer. ...
In my thesis, I achieved the following:
1. Optimization of CZE-UV and CZE-MS parameters for intact protein analysis in BFS, PB-coated, and LPA-coated capillaries, considering the ideal operating conditions for each capillary.
2. Evaluation and comparison of the separation performances of LPA-coated and PB-coated capillaries with BFS capillary for simple and complex protein mixtures.
3. Demonstration of ESI-MS's good detection sensitivity for smaller proteins (M < 25 kDa) and its limited sensitivity for numerous larger proteins (M > 30 kDa).
4. Utilization of CZE-MS for beneficial TDMS examinations of proteins, providing insights into intact proteins (from smaller peptides to large mAbs) and their deamidated isoforms.
... Generally, LCMS analysis of polar and non-volatile compounds include protonation, cationization, and electron ejection (positive ions), and deprotonation and electron capture for the generation of negative ions (Medhe, 2018;Siuzdak, 2004). Common ionization sources for the generation of these species include, but are not limited to, electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and matrix-assisted laser desorption ionization (MALDI). ...
... A number of research and/or review articles detailing both the advantages and challenges of these ionization techniques have been published (Cramer and Humpf, 2012;Fang et al., 2020;He et al., 2019;Lorenzo and Pico, 2017;Medhe, 2018;Siuzdak, 2004). During the last decade, there was an advancement in mass spectrometric ionization detection of chemicals called the ambient and miniature ionization mass spectrometric (AMIMS) technique, where ions are generated in an ion source outside the mass spectrometer. ...
Pharmaceutical compounds (PCs) have globally emerged as a significant group of environmental contaminants due to the constant detection of their residues in the environment. The main scope of this review is to fill the void of information on the knowledge on the African occurrence of selected PCs in environmental matrices in comparison with those outside Africa and their respective toxic actions on both aquatic and non-aquatic biota through ecotoxicity bioassays. To achieve this objective, the study focused on commonly used and detected pharmaceutical drugs (residues). Based on the conducted literature survey, Africa has the highest levels of ciprofloxacin, sulfamethoxazole, lamivudine, acetaminophen, and diclofenac while Europe has the lowest of all these PC residues in her physical environments. For ecotoxicity bioassays, the few data available are mostly on individual groups of pharmaceuticals whereas there is sparsely available data on their combined forms.
Data availability statement
Data will be made available on request.
... Mass spectrometry is an analytical technique that identifies the structure and chemical composition of any compound based on its mass-to-charge ratio [19,20]. It is a comprehensive technique that can identify the peptides/proteins, the sites of protein modification, its expression, and interaction with other biomolecules [21]. ...
Introduction
With available genomic data and related information, it is becoming possible to better highlight mutations or genomic alterations associated with a particular disease or disorder. The advent of high-throughput sequencing technologies has greatly advanced diagnostics, prognostics, and drug development.
Areas covered
Peptidomics and proteogenomics are the two post-genomic technologies that enable the simultaneous study of peptides and proteins/transcripts/genes. Both technologies add a remarkably large amount of data to the pool of information on various peptides associated with gene mutations or genome remodeling. A literature search was performed in the PubMed database and is up to date.
Expert Opinion
This article lists various techniques used for peptidomic and proteogenomic analyses. It also explains various bioinformatics workflows developed to understand differentially expressed peptides/proteins and their role in disease pathogenesis. Their role in deciphering disease pathways, cancer research, and biomarker discovery using non-invasive biofluids is highlighted. Finally, the challenges and future requirements to overcome the current limitations for their effective clinical use are also discussed.
... In the evaporative method, the solvent is evaporated in the samples generating the ions. Different techniques are employed according to the nature of the sample, the requirement, sensitivity and mass range of the methods (Awad et al., 2015;Medhe, 2018;Siuzdak, 2004). To protect the rights of the author(s) and publisher we inform you that this PDF is an uncorrected proof for internal business use only by the author(s), editor(s), reviewer(s), Elsevier and typesetter Thomson Digital. ...
Distinct physicochemical properties observed in nanomaterials (NM) have attracted enormous technological and scientific interest as it enables innovative functional applications. These functional properties of NM are interdependent on their size, shape, crystal structure, chemical composition, oxidation states, surface composition, and atomic defects, etc. Hence, a comprehensive understanding of NM composition–structure–property relationships using appropriate characterization techniques is of the utmost importance for the rational design of NM, and to fine-tune its functional properties. Therefore, the selection of the right probing mechanism to study its functional properties will provide informed decisions to select, and optimize appropriate synthesis approaches as per the application demand. Hence, the main objective of this chapter is to summarize different state-of-the-art characterization techniques based on the information they can provide, and the complementarity of the information supplied by various methods. Furthermore, the fundamental probing mechanism of different characterization tools, their strengths, and weaknesses are discussed. Thus, it will serve as a guide for the selection of appropriate characterization techniques for structural, compositional, and physicochemical characterization of NM.
... To analyze the content of individual elements in soils and plants, the selected samples were dried to an air-dry state, then weighed samples (2.0 g each). The content of elements in plant samples and soil was determined in the analytical laboratory of the Institute of Geology, RAS (Moscow) using ICP-MS (Plasma quad pq2-turbo plus, Usa) mass spectrometry with inductively coupled plasma (Medhe, 2017) The content of individual elements was expressed as the mass fraction of impurities -in parts per million (ppm). The actual material was selected for 10 years -from 2010 to 2018. ...
... Many heavy metals play an important role in plant life, regulate enzymatic activity, participate in redox processes, regulate the rate of formation of chlorophyll and carotenoids, change the intensity of photosynthesis, participate in carbohydrate and nitrogen cycle reactions, increase plant resistance against various fungal and bacterial diseases. With an excessive influx of heavy metals into the environment, negative changes occur in woody plants (Medhe, 2017). The negative impact of copper reduces the rate of formation of phytomass, leads to fall the water content in plant tissues and chlorophyll content in assimilation organs. ...
... LC system has been reported to offer advantages such as high sensitivity and selectivity even in complex matrices (Delatour et al. 2018;Masia et al. 2016;Mainero Rocca et al. 2017;Moreno-Bondi et al. 2009;Liu et al. 2011). By the advancements in ionization techniques such as electrospray ionization (ESI), matrix-assisted laser desorption ionization (MALDI), plasma desorption (Medhe, 2018), and use of different mass analyzers such as triple quadruple systems, ion trap, time of flight, and until recently, high-resolution mass spectrometers (Moreno-Bondi et al. 2009). LC can be used as an excellent tool for quantification of trace levels of these residues in complex food matrices such as honey, eggs, and plant and animal tissues (Stolker et al. 2007). ...
Developing a suitable method to detect the analytes of interest is of prime importance especially when it comes to multiclass methods. Which, in recent times, is gaining popularity due to its merits such as reduced time, reduced labor consumption, and lesser analytical runs. As the complexity of the matrix increases, selecting a suitable sample preparation technique becomes essential in order to increase the sensitivity and selectivity of the method. And finally, validation becomes a primary concern to determine whether the method developed is fit for its purpose. This review focuses on all these aspects with respect to the analysis of veterinary drugs present in food matrices. Furthermore, it also discusses recent trends in sample preparation techniques used specifically in animal-based/derived foods for the determination of veterinary drugs. Recent developments focusing on improving the sensitivity, recovery, and efficiency of the developed method through chemometrics has also been discussed in this review.
Graphical abstract.
Endocrine tumors derive from endocrine cells with high heterogeneity in function, structure and embryology, and are characteristic of a marked diversity and tissue heterogeneity. There are still challenges in analyzing the molecular alternations within the heterogeneous microenvironment for endocrine tumors. Recently, several proteomic, lipidomic and metabolomic platforms have been applied to the analysis of endocrine tumors to explore the cellular and molecular mechanisms of tumor genesis, progression and metastasis. In this review, we provide a comprehensive overview of spatially resolved proteomics, lipidomics and metabolomics guided by mass spectrometry imaging and spatially resolved microproteomics directed by microextraction and tandem mass spectrometry. In this regard, we will discuss different mass spectrometry imaging techniques, including secondary ion mass spectrometry, matrix-assisted laser desorption/ionization and desorption electrospray ionization. Additionally, we will highlight microextraction approaches such as laser capture microdissection and liquid microjunction extraction. With these methods, proteins can be extracted precisely from specific regions of the endocrine tumor. Finally, we compare applications of proteomic, lipidomic and metabolomic platforms in the field of endocrine tumors and outline their potentials in elucidating cellular and molecular processes involved in endocrine tumors.
