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A Comparative Study of Organic Pollutants in Seawater, Sediments, and Oyster Tissues at Hab River Delta, Balochistan Coast, Pakistan
Published in Se-Kwon Kim, Marine Biochemistry, 2023
Sadar Aslam, Malik Wajid Hussain Chan, Grzegorz Boczkaj, Ghazala Siddiqui
Molecules in GC analyses can be confirmed by comparing with co-injecting standards. Molecules with resembling chemical structures produce similar mass spectra and hence cannot be differentiated by mass spectrum alone. The equation propounded by van den Dool and Kratz (1963) for calculation for the linear retention index (LRI; used in temperature programming conditions) by following formula: where tn, tn + 1, and tx are net retention times, and n = carbon number.
Drug Design, Synthesis, and Development
Published in Nathan Keighley, Miraculous Medicines and the Chemistry of Drug Design, 2020
Chromatography can be coupled to mass spectrometry, MS, which enables the relative molecular mass of the analytes to be accurately determined and help to characterise product and contaminants. However, this will not give information on isomers. Spectroscopic techniques are required for complete characterisation. Infra-red spectroscopy is a quick and useful technique for identifying functional groups that are present in the molecule, but does not yield complete structural information and this is where nuclear magnetic resonance (NMR) spectroscopy is needed. This enables accurate structural characterisation, and information from coupling constants and integration can determine the proportion of each isomer present.
Analysis of Essential Oils
Published in K. Hüsnü Can Başer, Gerhard Buchbauer, Handbook of Essential Oils, 2020
Adriana Arigò, Mariosimone Zoccali, Danilo Sciarrone, Peter Q. Tranchida, Paola Dugo, Luigi Mondello
Mass spectrometry (MS) can be defined as the study of systems through the formation of gaseous ions, with or without fragmentation, which are then characterized by their mass to charge ratios (m/z) and relative abundances (Todd, 1995). The analyte may be ionized thermally, by an electric field or by impacting energetic electrons, ions, or photons.
ROS-sensitive calcipotriol nano-micelles prepared by methoxypolyethylene glycol (mPEG) – modified polymer for the treatment of psoriasis
Published in Drug Delivery, 2022
Yulin Hua, Tiantian Chang, Kun Jiang, Jinhong Wang, Xiaodong Cui, Min Cheng, Fang Yan, Bo Song, Yuzhen Wang
The synthetic mPEG raw material, the mPEG-SH intermediate, and the mPEG-SS end product were identified by hydrogen spectroscopy using CDCl3 as a solvent in a nuclear magnetic resonance spectrometer (BRUKER AVANCE 400 MHz) (Zhang et al., 2017). The molecular weight was determined by mass spectrum (MS). The mPEG-SS solutions with or without H2O2 (0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.20, 0.30, and 0.40 mmol/L) were prepared and added to the test cups. The test cups were kept at a constant temperature of 25 °C in the reaction bath. The hanging ring was cooled after removing the dirt with an alcohol blowtorch, and the surface tension of each sample was tested three times per group. The data were plotted, and the inflection point was the critical micellar concentration (CMC).
An integrated strategy for the comprehensive profiling of the chemical constituents of Aspongopus chinensis using UPLC-QTOF-MS combined with molecular networking
Published in Pharmaceutical Biology, 2022
Fengyu Zhang, Bichen Li, Ying Wen, Yanyang Liu, Rong Liu, Jing Liu, Shao Liu, Yueping Jiang
The untargeted identification strategy was as follows. The identification of unannotated points was based on the characterization of a similar mass spectrum of the same type of compound, and each MN was performed using the same type of compound. The classification of annotated points was analyzed in order to determine the type of network where they were located. Then, the unannotated peaks were processed according to the following steps. First, the element composition of unannotated points was automatically deduced by the formula predictor of the Qualitative Navigator B.08.00 software. The elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulphur (S) were selected to calculate the elemental composition of the compounds, and only consistent chemical formulas were considered. The maximum MS mass tolerance was set at ≤5 ppm. Second, the molecular formula predicted by the molecular predictor was uploaded into the SciFinder database (https://origin-scifinder.cas.org/scifinder/) to search for potential matching compounds. If they were found, the compound category was set to further filter the potential structural formula. Then, the fracture modes of the annotated points were summarised in the same network. The chromatographic characteristics and the MS/MS data, as well as the bibliographic information, were utilized for the identification of compounds. Potential structural formulas were verified by fragment ions and fracture modes to determine the structural formula of the unknown compound. Finally, Cytoscape 3.8.2 was used to visualize and edit the entire MN.
Molecular tissue profiling by MALDI imaging: recent progress and applications in cancer research
Published in Critical Reviews in Clinical Laboratory Sciences, 2021
Pey Yee Lee, Yeelon Yeoh, Nursyazwani Omar, Yuh-Fen Pung, Lay Cheng Lim, Teck Yew Low
MALDI imaging was initially introduced by Caprioli et al. [17] in the late 1990s. MALDI-MS was used for direct imaging of insulin and hormone peptides from rat tissue sections and provided detailed spatial localization of biomolecules that could be displayed as ion images. Since then, MALDI imaging techniques have been adopted in many studies to characterize molecular spatial distribution. It is a versatile analytical tool, applicable not only to protein and peptide analysis, but also to diverse classes of biomolecules including glycans, lipids, drugs, and metabolites [18]. The general workflow for MALDI imaging consists of several steps: (i) tissue sectioning and mounting onto a conductive glass slide, (ii) tissue coating with a homogenous layer of matrix, (iii) irradiation with a laser beam at a predefined number of shots across selected coordinates for data acquisition, (iv) analyte identification and data analysis, and (v) quantification. The mass spectrum comprised of a plot of ion intensity against m/z, is generated for each coordinate that corresponds to molecular content. The acquired dataset can be presented as an image map for each molecular ion across the tissue in a pseudo-color heat map indicating spatial intensity distribution [19]. After data acquisition, the same tissue section can be re-used for histological staining and co-registered with the MALDI imaging data to map the molecular ion to the tissue area [20] (Figure 2). We will discuss the key considerations for each of these steps below.