scholarly journals Mass spectrometry-based identification of ortho-, meta- and para-isomers using infrared ion spectroscopy

The Analyst ◽  
2020 ◽  
Vol 145 (18) ◽  
pp. 6162-6170
Author(s):  
Rianne E. van Outersterp ◽  
Jonathan Martens ◽  
Giel Berden ◽  
Valerie Koppen ◽  
Filip Cuyckens ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Drug Metabolism ◽  
Mass Spectrometric ◽  
Positional Isomers ◽  
Ion Spectroscopy ◽  
Significant Challenge

Distinguishing positional isomers presents a significant challenge for mass spectrometric analyses, for instance in drug metabolism research. We show that IR ion spectroscopy readily identifies ortho-, meta- and para-isomers.

scholarly journals Mass Spectrometry-Based Identification of Ortho-, Meta- and Paraisomers Using Infrared Ion Spectroscopy

2020 ◽  
Author(s):  
Rianne E. van Outersterp ◽  
Jonathan Martens ◽  
Giel Berden ◽  
Valerie Koppen ◽  
Filip Cuyckens ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Ir Spectra ◽  
Distinct Pattern ◽  
Positional Isomers ◽  
Specific Chemical ◽  
Ion Spectroscopy ◽  
Significant Challenge ◽  
Substituent Group ◽  
Direct Interpretation ◽  
Ir Bands

Distinguishing positional isomers, such as compounds having different substitution patterns on an aromatic ring, presents a significant challenge for mass spectrometric analyses and is a frequently encountered difficulty in, for example, drug metabolism research. Here, we demonstrate infrared ion spectroscopy (IRIS) as a promising new mass spectrometry-based technique that easily differentiates between positional isomers of disubstituted phenyl-containing compounds. By analyzing different substitution patterns over several sets of isomeric compounds, we show that IRIS produces a highly consistent and distinct pattern of IR bands, especially in the range between 650 and 900 cm<sup>-1</sup>, that are mostly independent of the specific chemical functionality contained in the substituent group. These patterns are accurately predicted by quantum-chemically computed IR spectra and correspond well with tabulated IR group-frequencies known from conventional absorption spectroscopy. Therefore, we foresee that this method will be generally applicable to disubstituted phenyl-containing compounds and that direct interpretation of experimental IRIS spectra in terms of ortho-, meta- or para-substitution is possible, even without comparison to experimental or computationally predicted reference spectra. Strategies for the analysis of larger compounds having more congested IR spectra as well as of compounds having low (electrospray) ionization efficiencies are presented in order to demonstrate the broad applicability of this methodology.<br>

scholarly journals Mass Spectrometry-Based Identification of Ortho-, Meta- and Paraisomers Using Infrared Ion Spectroscopy

2020 ◽  
Author(s):  
Rianne E. van Outersterp ◽  
Jonathan Martens ◽  
Giel Berden ◽  
Valerie Koppen ◽  
Filip Cuyckens ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Ir Spectra ◽  
Distinct Pattern ◽  
Positional Isomers ◽  
Specific Chemical ◽  
Ion Spectroscopy ◽  
Significant Challenge ◽  
Substituent Group ◽  
Direct Interpretation ◽  
Ir Bands

Distinguishing positional isomers, such as compounds having different substitution patterns on an aromatic ring, presents a significant challenge for mass spectrometric analyses and is a frequently encountered difficulty in, for example, drug metabolism research. Here, we demonstrate infrared ion spectroscopy (IRIS) as a promising new mass spectrometry-based technique that easily differentiates between positional isomers of disubstituted phenyl-containing compounds. By analyzing different substitution patterns over several sets of isomeric compounds, we show that IRIS produces a highly consistent and distinct pattern of IR bands, especially in the range between 650 and 900 cm<sup>-1</sup>, that are mostly independent of the specific chemical functionality contained in the substituent group. These patterns are accurately predicted by quantum-chemically computed IR spectra and correspond well with tabulated IR group-frequencies known from conventional absorption spectroscopy. Therefore, we foresee that this method will be generally applicable to disubstituted phenyl-containing compounds and that direct interpretation of experimental IRIS spectra in terms of ortho-, meta- or para-substitution is possible, even without comparison to experimental or computationally predicted reference spectra. Strategies for the analysis of larger compounds having more congested IR spectra as well as of compounds having low (electrospray) ionization efficiencies are presented in order to demonstrate the broad applicability of this methodology.<br>

Confounding contaminants in mass spectrometric reaction monitoring

2018 ◽  
Author(s):  
Gilian T. Thomas ◽  
Landon MacGillivray ◽  
Natalie L. Dean ◽  
Rhonda L. Stoddard ◽  
Lars Yunker ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectrometric ◽  
Negative Ion ◽  
Reaction Monitoring ◽  
Schlenk Flask ◽  
Dynamic Analyses ◽  
Rubber Septa ◽  
Negative Ion Mode ◽  
Mode A

<p>Reactions carried out in the presence of rubber septa run the risk of additives being leached out by the solvent. Normally, such species are present at low enough levels that they do not interfere with the reaction significantly. However, when studying reactions using sensitive methods such as mass spectrometry, the appearance of even trace amounts of material can confuse dynamic analyses of reactions. A wide variety of additives are present in rubber along with the polymer: antioxidants, dyes, detergent, and vulcanization agents, and these are all especially problematic in negative ion mode. A redesigned Schlenk flask for pressurized sample infusion (PSI) is presented as a means of practically eliminating the presence of contaminants during reaction analyses.</p>

Resolution of a protein sequence ambiguity by X-ray crystallographic and mass spectrometric methods

1992 ◽  
Vol 25 (2) ◽  
pp. 205-210 ◽  
Author(s):  
L. J. Keefe ◽  
E. E. Lattman ◽  
C. Wolkow ◽  
A. Woods ◽  
M. Chevrier ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Amino Acid ◽  
Electron Density ◽  
Mass Spectrometric ◽  
Amino Acid Sequences ◽  
Data Matrix ◽  
Protein Crystal ◽  
Insertion Mutant ◽  
Laser Desorption Mass Spectrometry ◽  
X Ray

Ambiguities in amino acid sequences are a potential problem in X-ray crystallographic studies of proteins. Amino acid side chains often cannot be reliably identified from the electron density. Many protein crystal structures that are now being solved are simple variants of a known wild-type structure. Thus, cloning artifacts or other untoward events can readily lead to cases in which the proposed sequence is not correct. An example is presented showing that mass spectrometry provides an excellent tool for analyzing suspected errors. The X-ray crystal structure of an insertion mutant of Staphylococcal nuclease has been solved to 1.67 Å resolution and refined to a crystallographic R value of 0.170 [Keefe & Lattman (1992). In preparation]. A single residue has been inserted in the C-terminal α helix. The inserted amino acid was believed to be an alanine residue, but the final electron density maps strongly indicated that a glycine had been inserted instead. To confirm the observations from the X-ray data, matrix-assisted laser desorption mass spectrometry was employed to verify the glycine insertion. This mass spectrometric technique has sufficient mass accuracy to detect the methyl group that distinguishes glycine from alanine and can be extended to the more common situation in which crystallographic measurements suggest a problem with the sequence, but cannot pinpoint its location or nature.

Vitamin D analyses in veterinary feeds by gas chromatography-tandem mass spectrometry

2021 ◽  
pp. 146906672110002
Author(s):  
Andreas Lehner ◽  
Margaret Johnson ◽  
Alan Zimmerman ◽  
Justin Zyskowski ◽  
John Buchweitz
Keyword(s):  
Mass Spectrometry ◽  
Vitamin D ◽  
Gas Chromatography ◽  
Liquid Chromatography ◽  
Tandem Mass Spectrometry ◽  
Vitamin D3 ◽  
Mass Spectrometric ◽  
Chromatographic Behavior ◽  
Tandem Mass ◽  
Chromatography Tandem Mass Spectrometry

This report examines the feasibility of determination of Vitamin D3, D2 and their 25-hydroxy metabolites utilizing Gas Chromatography Tandem Mass Spectrometry (GC/MS/MS) as a potential alternative to popular Liquid Chromatography Tandem Mass Spectrometric (LC/MS/MS) methodologies. The GC/MS/MS approach was found to operate reasonably well despite long-standing concerns that gas-liquid chromatography of vitamin D compounds invoke thermal rearrangements owing to the relatively high inlet and capillary column temperatures used. The workup procedure involved incubation of feed samples with concentrated potassium hydroxide for overnight fat saponification, extraction of D Vitamins in n-hexane and reaction with N,O-bis(trimethylsilyl)trifluoroacetamide at 70 °C for 30 mins. In addition to parent compounds, small amounts of pyro-, isopyro-, and iso-vitamin D and isotachysterol3 variants were obtained from each Vitamin D-related compound upon extraction and GC/MS/MS analysis. Mass spectral and chromatographic behavior of these compounds are herein described and interpreted. Multiple Reaction Monitoring settings on GC/MS/MS included m/z 456→351 for Vitamin D3 and m/z 486→363 for Vitamin D2. Trimethylsilylation enabled single predominant peaks for Vitamins D3 and D2, and sample workup in the presence of deuterated Vitamin D analogs enabled accurate and precise sensitivity to 1 ppb (ng/g) in feeds. The method could be extended with reasonable accuracy to 25-hydroxy (25OH) compounds, but accuracies would be significantly improved by inclusion of respective 25OH-specific deuterated internal standards. The method was applied to 27 submissions of suspect dog foods of which 22% were discovered elevated and 44% were discovered to contain toxic levels of Vitamin D3. The described method was thus discovered to provide a suitable mass spectrometric approach for Vitamin D, proving itself here specifically of value in detection of ergocalciferol and cholecalciferol in animal feeds. The specificity and sensitivity of the tandem quadrupole approach can enable suitable applicability to serum determination if desired.

scholarly journals Quantitative imaging mass spectrometry of renal sulfatides: validation by classical mass spectrometric methods

2014 ◽  
Vol 55 (11) ◽  
pp. 2343-2353 ◽  
Author(s):  
Christian Marsching ◽  
Richard Jennemann ◽  
Raphael Heilig ◽  
Hermann-Josef Gröne ◽  
Carsten Hopf ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Quantitative Imaging ◽  
Imaging Mass Spectrometry ◽  
Mass Spectrometric
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