Mass spectrometry最新文献

A novel ionization technique named medium vacuum chemical ionization (MVCI) mass spectrometry (MS), which is a chemical ionization using oxonium (H₃O⁺) and hydroxide (OH^-) formed from water, has excellent compatibility with the supercritical fluid extraction (SFE)/supercritical fluid chromatography (SFC). We have studied a method to determine free fatty acids (FFAs) in a small section of bovine liver tissue using SFE/SFC-MVCI MS analysis without further sample preparation. A series of FFA molecules interact with the C18 stationary phase, exhibiting broad chromatographic peaks when using a non-modified CO₂ as the mobile phase. It can be optimized by adding a small content of methanol to the mobile phase as a modifier; however, it may dampen the ionization efficiency of MVCI since the proton affinity of methanol is slightly higher than water. We have carefully evaluated the modifier content on the ion detection and column efficiencies. The obtained result showed that an optimized performance was in the range of 1 to 2% methanol-modified CO₂ mobile phase for both column efficiency and peak intensity. Higher methanol content than 2% degrades both peak intensity and column efficiency. Using optimized SFC conditions, a section of bovine liver tissue sliced for 14 µm thickness by 1 mm square, which is roughly estimated as about 3300 hepatocytes, was applied to determine 18 FFAs amounts for carbon chains of C12-C24. An amount of each tested FFA was estimated as in the range of 0.07 to 2.6 fmol per cell.

This study investigates the mass spectrometric analysis of 10 novel amidoamine oxide compounds, which are innovative hydrogelators for polar solvents. This research aims to identify characteristic fragment patterns for these amide compounds using high-resolution mass spectrometry. Methanol solutions of the compounds were analyzed in positive and negative ion modes, and MS1 and MS2 spectra at 6 collision energy levels were obtained via electrospray ionization and hybrid tandem mass spectrometry. The importance of low-intensity peaks in structure elucidation was emphasized because low-intensity fragments could provide crucial structural information, especially for compounds with similar structures. Chain-length-dependent fragmentation patterns were observed, which could aid in predicting the structures of related compounds. This research highlights the challenges of balancing informative low-intensity peaks with accurate spectral matching in databases. Based on our results, combining mass spectrometry with separation techniques, such as liquid chromatography, could enhance structural elucidation for unknown compounds. This study contributes to the broader field of mass spectrometry and structural chemistry, particularly in the analysis of amide compounds, and future directions are proposed for developing robust algorithms for selecting and interpreting low-intensity peaks to improve compound identification in complex mixtures.

In this study, we employed platinum-assisted surface-assisted laser desorption/ionization mass spectrometry imaging (MSI) (Pt-SALDI-MSI) to detect and visualize the spatial distribution of antioxidant additives and organic dyes in polystyrene films undergoing photodegradation. In traditional matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), matrix-derived ion peaks often obscure signals from low-molecular-weight analytes. Pt-SALDI-MSI, which utilizes inorganic nanoparticles instead of an organic matrix, enables the interference-free analysis of low-molecular-weight compounds, thereby addressing the limitation of traditional MALDI-MS. Using Pt-SALDI-MSI, we observed the degradation and distribution of Irganox 1098 (an antioxidant) and crystal violet (an organic dye) following ultraviolet irradiation. This method effectively captures the photodegradation process, providing valuable insights into the environmental breakdown of plastics and the formation of microplastics.

A simple and rapid analytical method was developed for the simultaneous determination of two chromium species, Cr(III) and Cr(VI), in the environmental waters by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). This study incorporated a chelating pretreatment with 2,6-pyridinedicarboxylic acid (PDCA) to convert Cr(III) species into a stable Cr(III)-PDCA anion complex, which was then separated from Cr(VI) oxyanion using an anion exchange column. Building on the fundamental analytical approach proposed by Shigeta et al. (doi: 10.2116/analsci.18P012), the mobile phase was optimized to ensure stability for ICP-MS detection, avoiding nonvolatile salts. Chromium species and chloride ions were effectively separated within 6 minutes at a flow rate of 0.6 mL min^-1 with the optimized mobile phase, which consisted of 50 mmol L^-1 ammonium acetate (pH 6.80) and 2 mmol L^-1 PDCA. The detection limits were 0.18 μg L^-1 and 0.09 μg L^-1 for Cr(III) and Cr(VI), respectively, at m/z 52 under He collision mode.

Choline-containing compounds are essential nutrients for human activity, as they are involved in many biological processes, including cell membrane organization, methyl group donation, neurotransmission, signal transduction, lipid transport, and metabolism. These compounds are normally obtained from food. Fermented brown rice and rice bran with Aspergillus oryzae (FBRA) is a fermented food product derived from rice and rice ingredients. FBRA exhibits a multitude of functional properties with respect to the health sciences. This study has a particular focus on choline-containing compounds. We first developed a simultaneous liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis method for seven choline-containing compounds. The method was subsequently applied to FBRA and its ingredients. Hydrophilic interaction chromatography (HILIC) and selected reaction monitoring were employed for the simultaneous analysis of seven choline-containing compounds. MS ion source conditions were optimized in positive ion mode, and the product ions derived from the choline group were obtained through MS/MS optimization. Under optimized HILIC conditions, the peaks exhibited good shape without peak tailing. Calibration curves demonstrated high linearity across a 300- to 10,000-fold concentration range. The application of the method to FBRA and other ingredients revealed significant differences between food with and without fermentation. In particular, betaine and α-glycerophosphocholine were found to be highest in FBRA and brown rice malt, respectively. The results indicated that the fermentation processing of rice ingredients results in alterations to the choline-containing compounds present in foods. The developed HILIC/MS/MS method proved to be a valuable tool for elucidating the composition of choline-containing compounds in foods.

Intermolecular interactions between aromatic amino acids were investigated by ultraviolet photodissociation spectroscopy of hydrogen-bonded protonated clusters of histidine (His) and tryptophan (Trp) enantiomers in the gas phase. Product ion spectra and photodissociation spectra in the wavelength range of the S₁-S₀ transition of Trp at several temperatures (8-100 K) were obtained using a tandem mass spectrometer equipped with an electrospray ionization source and a cold ion trap. l-Trp detachment forming protonated His was the main pathway. Two bands observed at 288 and 285 nm in the photodissociation spectra of heterochiral H⁺(d-His)(l-Trp) indicated the coexistence of two types of conformers. The bands at 288 and 285 nm were attributed to the conformers formed from stronger and weaker intermolecular interactions, respectively. In the spectra of homochiral H⁺(l-His)(l-Trp), only the band due to the stronger interactions was observed at 288 nm. The intermolecular interactions of l-His with l-Trp were stronger than those of d-His with l-Trp.

In the interpretation step of mass spectra obtained from synthetic polymers, isotope peaks are typically intense and cannot be ignored, especially in the higher mass range. To reduce the complexity of the spectra, deisotope processing is used. In this study, a deisotope processing method that is effective even for mixtures of different types of polymers is investigated.

Plant alkaloids are used in a variety of medicines, such as anti-cancer drugs and analgesics. Among these plant alkaloids, galanthamine is an Amaryllidaceae type alkaloid with acetylcholinesterase inhibition activity used in the treatment of neurological diseases such as Alzheimer's disease. Although the chemical synthesis of galanthamine has been successfully achieved, Narcissus tazetta is the main source of its production. Research shows that the galanthamine content varies not only with the type of daffodil but also with the stage of development and the part of the plant. Pharmaceutical companies seek plant species with higher galanthamine content to increase pharmaceutical availability. In this study, we were able to rapidly confirm the presence of alkaloids, such as galanthamine, lycorine, and tazettine in the N. tazetta sample using the probe electrospray ionization coupled with quadrupole time-of-flight type mass spectrometry. After confirmation of the components, we then visualized the distribution of the alkaloids by mass spectrometry imaging using the atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometer. In our method, we can provide qualitative data and visualized data immediately.

Mass spectrometry (MS) is a valuable tool that enables label-free analysis and the ability to measure multiple molecules. The atmospheric pressure MS imaging (MSI) method usually requires tedious sample preparation. A simple ionization method with minimal sample preparation is needed for high-throughput analysis. We have developed an ion source that does not require sample preparation such as thinning, curing, planarization, or addition of matrix by the electrospray-assisted laser desorption/ionization with gas transportation (ELDI-GT). The sample is transported with nitrogen gas through a heated tube to the electrospray. The ion signal of protonated caffeine was measured under different transport conditions. The ion signal intensity was found to increase 11-fold by changing the flow rate and tube temperature from 2.8 cm³/s and 473 K to 25 cm³/s and 673 K. ELDI-GT was able to visualize the localization of caffeine crystals at a pixel size of 50 µm using MSI because of the effective GT using the heated tube. The dependence of the ion signal intensity was discussed on the amount of heat applied to the sample in the heated tube. ELDI-GT allowed accurate localization of caffeine at a pixel size of 50 µm without the need to apply thinning and matrix to a sample.

Matrix-assisted laser desorption ionization (MALDI) and surface-assisted laser desorption ionization (SALDI) mass spectrometry (MS), which can detect biomolecules and polymers, are widely used in biochemistry and material science. Some compounds that are difficult to ionize using MALDI can be ionized using SALDI. However, it is difficult to obtain high ion yields using SALDI/MS. In this study, a fabricated platinum (Pt) film with nanostructures on the sample surface using a sputtering method was evaluated to determine the optimal metal film for ion yield in SALDI. The surface morphology of the Pt film was analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray reflectivity (XRR), and ultraviolet-visible-near-infrared (UV-Vis-NIR) reflectance spectroscopy. The SEM, AFM, and TEM images of the Pt film showed the deposited metal film giving high ion yields of polyethylene glycol (PEG) in SALDI/MS with a Pt film (Pt-SALDI) that had a rough surface. The densities and reflectivity of films were analyzed by XRR and UV-Vis-NIR. The higher ion yields of PEG were obtained by Pt-SALDI with the Pt films with lower densities and reflectivity. This indicates that the deposition conditions for the Pt films significantly improved the ion yield in Pt-SALDI/MS. The Pt-SALDI has ionization capabilities different from those of MALDI. Therefore, optimization of Pt film for SALDI/MS and the MS imaging allows more compounds to be detected with higher sensitivity.