• Mass Spectrometry Letters
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• 제3권2호
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• pp.29-38
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• 2012

A new approach of volatile compounds analysis is proposed using a linear ion trap Orbitrap mass spectrometer coupled with gas chromatography through an atmospheric pressure photoionization interface. In the proposed GC-HRMS/MS approach, direct chemical composition analysis is made for the precursor ions in high resolution MS spectra and the structural identifications were made through the database search of high quality MS/MS spectra. Successful analysis of a complex perfume sample was demonstrated and compared with GC-EI-Q and GC-EI-TOF. The current approach is complementary to conventional GC-EI-MS analysis and can identify low abundance co-eluting compounds. Toluene co-sprayed as a dopant through API probe significantly enhanced ionization of certain compounds and reduced oxidation during the ionization.

• Bulletin of the Korean Chemical Society
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• 제26권4호
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• pp.575-578
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• 2005

Electrospray ionization mass spectrometry (ESI MS) was used, along with gas chromatography-mass spectrometry (GC-MS), to monitor Paal-Knorr synthesis of 2,5-dimethyl-1-phenylpyrrole by condensation of aniline with 2,5-hexanedione. In addition to 2,5-dimethyl-1-phenylpyrrole observed as a single spot by TLC, unexpected dimer size compounds were observed by GC-MS. Dimers and trimers were observed by ESI MS. ESI tandem mass spectrometry was used to select plausible structures for the dimer. ESI MS with or without liquid chromatographic separation is useful for observing oligomeric byproducts with low volatility produced in organic reactions.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.919-924
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• 2014

Ambient ionization can be achieved by generating an electrospray directly from plant tissue ("leaf spray"). The resulting mass spectra are characteristic of ionizable phytochemicals in the plant material. By subtracting the leaf spray spectra recorded from the petals of two hibiscus species H. moscheutos and H. syriacus one gains rapid access to the metabolites that differ most in the two petals. One such compound was identified as the sambubioside of quercitin (or delphinidin) while others are known flavones. Major interest centered on a $C_{19}H_{29}NO_5$ compound that occurs only in the large H. moscheutos bloom. Attempts were made to characterize this compound by mass spectrometry alone as a test of such an approach. This showed that the compound is an alkaloid, assigned to the polyhydroxylated pyrrolidine class, and bound via a $C_3$ hydrocarbon unit to a monoterpene.

• Mass Spectrometry Letters
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• 제9권4호
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• pp.91-94
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• 2018

Bilin tetrapyrroles are metabolic products of the breakdown of porphyrins within a species. In the case of mammals, these bilins are formed by the catabolism of heme and can be utilized as either biomarkers in disease or as an indicator of human waste contamination. Although a small subset of bilin tandem mass spectrometry reports exist, limited data is available in online databases for their fragmentation. The use of fragmentation data is important for metabolomics analyses to determine the identity of compounds detected within a sample. Therefore, in this study, the fragmentation of bilins generated by positive ion mode electrospray ionization is examined by collision-induced dissociation (CID) as a function of collision energy on an FT-ICR MS. The use of the FT-ICR MS allows for high mass accuracy measurements, and thus the formulas of resultant product ions can be ascertained. Based on our observations, fragmentation behavior for hemin, biliverdin and its dimethyl ester, phycocyanobilin, bilirubin, bilirubin conjugate, mesobilirubin, urobilin, and stercobilin are discussed in the context of the molecular structure and collision energy. This report provides insight into the identification of structures within this class of molecules for untargeted analyses.

• Bulletin of the Korean Chemical Society
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• 제23권9호
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• pp.1247-1252
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• 2002

Mass-analyzed threshold ionization (MATI) technique is optimized to generate substantial amount of state-selected molecular ions sufficient for dynamics study. The main strategy is to stabilize intermediate (n = 100- 200) Rydberg states by l,m-mix ing induced by AC field. Electrical jitter inherent in high voltage switching is utilized for this purpose. A related technique to locate the MATI onset is also described.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.315-319
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• 2002

Visible surface-assisted desorption/ionization mass spectrometry (SALDI-MS) has been investigated for several small macromolecules deposited on the graphite plate using laser radiation at 532 nm where most of the macromolecules are transparent. The graphite surface functioned well as a photon absorbing material and an energy transfer mediator for visible light. The results show that visible SALDI is a much softer ionization technique than UV-MALDI and FAB-MS in our results with synthetic macromolecules, PPG, PPGMBE and cavitand molecules. For the SALDI of biomolecules, glycerol as a proton source was essential with the graphite plate. As in visible SALDI, the role division of the photon absorbing material and the cationization agent can provide a generality in mass spectrometric analysis of macromolecules compared with MALDI using the dual functional matrix.

• Mass Spectrometry Letters
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• 제13권3호
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• pp.49-57
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• 2022

During electrospray ionization mass spectrometry (ESI-MS) analysis of proteins, the addition of supercharging agents allows for adjusting the maximal charge state, affecting the charge state distribution, and increases the number of ions reaching the detector thus, improving signal detection. We postulate that in di-substituted arene isomers, molecules with higher polarizability values should generate greater interactions and hence elicit higher signal intensities. Polarizability is an electronic parameter which has been demonstrated to predict many chemical interactions. Many properties can be predicted based on charge polarization. Molecular polarizability is a vital descriptor for explaining intermolecular interactions. We employed DFT (density functional/Hartree-Fock hybrid model, B3LYP)-derived descriptors and computed molecular polarizability for ten disubstituted arene reagents, each set made up of three (ortho, meta, para) isomers, with reported use as supercharging reagents during ESI experiments. The atomic electronic inputs were ionization potential (IP), electron affinity (EA), electronegativity (𝛘), hardness (η), chemical potential (µ), and dipole moment (D). We determined that the para isomers showed the highest polarizability values in nine of the ten sets. There was no difference between the ortho and meta isomers. Polarizability also increased with increasing complexity of the substituents on the benzene ring. Polarizability correlated positively with IP, EA, 𝛘, η, and D but correlated negatively with chemical potential. This DFT study predicts that the para isomers of di-substituted arene isomers should elicit the strongest ESI responses. An experimental comparison of the three isomers, especially of larger supercharging molecules, could be carried out to establish this premise.

• Mass Spectrometry Letters
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• 제4권1호
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• pp.21-23
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• 2013

The effects of trifluoroacetic acid (TFA) were evaluated on the generation of multiply charged ions of cytochrome c in a 2-nitrophloroglucinol (2-NPG) matrix in high-vacuum, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The presence of 1% TFA in the 2-NPG matrix solution was more effective in generating multiply charged protein ions than matrix solutions containing 0.1% or 0% TFA. Regarding the matrix itself, with 1% TFA, 2-NPG was significantly more effective in generating multiply charged ions than 2,5-dihydroxybenzoic acid (2,5-DHB). The maximum charge state of cytochrome c was +8 when using a 2-NPG matrix containing 1% TFA.

• Mass Spectrometry Letters
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• 제12권4호
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• pp.159-162
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• 2021

The fragmentation pattern of four hindered phenol antioxidants was investigated using ammonium and lithium ions as the additives for ionization. Due to different binding geometries and interactions, they underwent different characteristic fragmentation reactions providing useful complementary information for structural analysis of hindered phenol antioxidants. Ammonium ion adducts were fragmented successively until all t-butyl groups were lost in the form of isobutylene and allowed the estimation of the number of t-butyl groups present in the molecule. Lithium ion adducts produced fragment ions from major backbone cleavage, on the other hand, which provide more crucial information for the identification of detailed backbone structure.

• Mass Spectrometry Letters
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• 제12권3호
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• pp.93-105
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• 2021

Exosomes have gained the attention of the scientific community because of their role in facilitating intercellular communication, which is critical in disease monitoring and drug delivery research. Exosome research has grown significantly in recent decades, with a focus on the development of various technologies for isolating and characterizing exosomes. Among these efforts is the use of matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS), which offers high-throughput direct analysis while also being cost and time effective. MALDI is used less frequently in exosome research than electrospray ionization due to the diverse population of extracellular vesicles and the impurity of isolated products, both of which necessitate chromatographic separation prior to MS analysis. However, MALDI-MS is a more appropriate instrument for the analytical approach to patient therapy, given it allows for fast and label-free analysis. There is a huge drive to explore MALDI-MS in exosome research because the technology holds great potential, most notably in biomarker discovery. With methods such as fingerprint analysis, OMICs profiling, and statistical analysis, the search for biomarkers could be much more efficient. In this review, we highlight the potential of MALDI-MS as a tool for investigating exosomes and some of the possible strategies that can be implemented based on prior research.