Laser Desorption Ionization-time Of Flight-mass Spectrometry Research Articles

Laser Ablation Synthesis of Tellurium Carbides using Nanocomposite of Tellurium with Nanodiamonds.

Carbides, including tellurium carbides (TeC), play crucial roles in diverse applications, but TeC synthesis has not been described in the literature. Laser ablation synthesis (LAS) coupled with mass spectrometry was used here for in situ TeC clusters synthesis and identification of the reaction products to better understand TeC formation. Laser desorption ionization time-of-flight mass spectrometry (LDI-TOFMS) was used to generate the TeC clusters and determine their stoichiometry via computer modeling of isotopic patterns. A simple one-pot procedure for Te-nanodiamonds nanocomposite preparation was developed. A suspension of fine powdered Te was mixed with a suspension of nanodiamonds (both in acetonitrile), and the resulting precipitated nanocomposite was suitable for the generation of TemCn clusters by LDI. Various unary and binary clusters were formed. The stoichiometry of the novel TemCn clusters, determined via computer modeling of isotopic patterns, is reported here for the first time. The Te-nanodiamonds composite was found to be the most suitable precursor for the generation of TemCn clusters. In total 35 binary TemCn clusters were identified, when several of them were not obtained using commercial TeC material.

Exploring the Chemical Structures and Phototochemical Properties of Graphene Oxide Derivatives by Laser Desorption/Ionization Time-of-Flight Mass Spectrometry to Develop an Efficient Platform for Mass Spectrometric Analysis.

Laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) analysis is harnessed to investigate the chemical structure and photochemical properties of two distinct graphene oxide (GO) derivatives simultaneously. The GO derivatives are synthesized with modified Brodie's method (BGO) and Hummers' method (HGO) and characterized by LDI-TOF-MS as well as conventional tools. A series of LDI-TOF-MS analyses reveal that BGO provides higher laser energy absorption, photochemical stability, and photothermal conversion property than HGO based on their fragmentation patterns and laser desorption/ionization behavior of a thermometer molecule. Based on these characteristics, BGO exhibits higher efficiency in the LDI-TOF-MS analysis of various small molecules and synthetic polymers than HGO. These different photochemical properties of BGO are derived from its large sp2 carbon domains compared to HGO. Based on our findings, the analytical potential of LDI-TOF-MS for GO derivatives is clearly demonstrated, which can be an efficient and unique characterization tool to explore both chemical structures and photochemical properties of various carbon materials.

Ti3C2(OH)x-assisted LDI-TOF-MS for the rapid analysis of natural small molecules.

The inhomogeneous distribution of co-crystallized analytes and the traditional organic matrices as well as the intensive background interference in the low molecular weight range hinder the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) in the analysis of small-molecular compounds. New two-dimensional material MXene (e.g., Ti3C2) exerts better hydrophilicity, homogeneity and repeatability, and higher laser desorption efficiency, as well as less background interference than traditional organic matrices and other nanomaterial matrices such as titanium oxide, graphene, and gold nanostructures. This study was aimed to design Ti3C2 matrix with abundant hydroxyls on its surface, enhance the stability of this hydroxyl-rich Ti3C2 (Ti3C2(OH)x), and evaluate the analytical performances of Ti3C2(OH)x-assisted laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) for small-molecular natural compounds in complex samples. The developed Ti3C2(OH)x showed the distinct advantages such as minimum background interference, high peak intensity (~105), high salt (0.6 M) and protein (0.5 mg/mL) tolerance, good repeatability (relative standard deviation<20%), and good stability after eight months of storage. Ti3C2(OH)x-assisted LDI-TOF-MS analysis could be used to rapidly identify Artemisia annua (a world-famous traditional Chinese medicine) and quantify the contents of the main chemical ingredients (oxymatrine (OXY) and matrine) of Compound Kushen Injection (CKI). Interestingly, the content of OXY in CKI could be accurately quantified by Ti3C2(OH)x-assisted LDI-TOF-MS, and there was a good linear relationship (R2 -0.9929), a low limit of detection (400 pg), and a low limit of quantification (600 pg) of OXY. Taken together, the rapid and accurate analysis of small-molecular natural compounds in complicated samples could be achieved by the Ti3C2(OH)x-assisted LDI-TOF-MS analysis.

Investigation of the Ligand Exchange Process on Gold Nanorods by Using Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

The ligand exchange process on gold nanorods (Au NRs) was explored by using laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS). Cetyltrimethylammonium bromide (CTAB) adsorbed on Au NRs was replaced with alkanethiol derivatives presenting different functional groups. The ligand exchange process was investigated under various conditions, such as in the presence of different functional groups in the ligands and with different concentrations of CTAB. The ligand-exchanged Au NRs were characterized by using a combination of UV–Vis spectroscopy and LDI-TOF-MS. Based on the results, it was revealed that LDI-TOF-MS analysis can provide crucial and distinct information about the degree of ligand exchange on Au NRs.

Quantitative analysis of galactose using LDI-TOF MS based on a TiO2 nanowire chip

A novel method for quantifying galactose was developed to serve as a newborn screening test for galactosemia using laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry (MS) with a TiO2 nanowire chip. Herein, phosphate citrate buffer, serum, and dried blood spot (DBS) were employed for the quantitative analysis of galactose. To quantitatively analyze galactose, its reduction potential was used to oxidize o-phenylene diamine (OPD) into 2,3-diaminophenazine (DA), which were both detected using LDI-TOF MS with a TiO2 nanowire chip according to the concentration of galactose. The reproducibility and the interference of glucose were determined to demonstrate the applicability of this method. Moreover, mixtures of galactose, phenylalanine, and 17 α-OHP were analyzed to determine the interference induced by other biomarkers of metabolic disorders. The OPD oxidation of galactose was found to be selectively achieved under high-glucose conditions, similar to human blood, thereby showing good reproducibility. The intensities of the mass peaks of OPD and DA based on LDI-TOF MS with a TiO2 nanowire chip were linearly correlated in the galactose concentration range of 57.2–220.0 μg/mL (r2 = 0.999 and 0.950, respectively) for serum samples and 52.5–220.0 μg/mL (r2 = 0.993 and 0.985, respectively) for DBS after methanol precipitation/extraction. The enzyme immunoassay and LDI-TOF MS analysis results were statistically analyzed, and a mixture of phenylalanine, 17 α-OHP, and galactose was simultaneously investigated quantitatively at the cutoff level.

Successive Free-Radical C(sp 2 )–C(sp 2 ) Coupling Reactions to Form Graphene

Successive Free-Radical C(sp ² )–C(sp ² ) Coupling Reactions to Form Graphene

Li+ and Na+ attachment to some dipeptides via LDI-TOF mass spectrometry: Fragmentation patterns

Laser desorption ionization-time of flight (LDI-TOF) mass spectrometry is used for studying the attachment of Na+ and Li+ ions to four dipeptides including phenylalanyl-alanine (Phe-Ala), tyrosyl-alanine (Tyr-Ala), L-Phenylalanyl-L-Phenylalanine (Phe-Phe), and alanyl-glutamine (Ala-Gln) dipeptides. The LiCl, NaOH, and NaF salts are used as the source of Li+ and Na+ ions in the LDI of the dipeptides. Our aim is the investigation of the difference between the fragmentation patterns of the selected dipeptides in the presence of Na+ and Li+ ions due to the laser radiation and providing information for the fragmentation of larger peptides in the same conditions. The characteristic peak, related to [dipeptide-H + 2Na]+ species, is observed in the mass spectrum of Phe-Ala and Tyr-Ala dipeptides in the presence of NaF, while the breaking of the peptide bond (OC-NH) occurs for the Phe-Phe in the presence of the aforementioned salts. The characteristic peak of Ala-Gln dipeptide ([(Ala-Gln)-H + 2Na]+) is observed in the absence of any salt. The mass spectra of the dipeptides, recorded in the presence of LiCl, are crowded compared to those recorded in the presence of NaF and NaOH showing the effect of the type of alkali salt on the dipeptide fragmentation. The theoretical calculations are employed to investigate the ability of the interaction sites of dipeptides for the attachment of one and two Na+ and determine the most stable structure of the [dipeptide-H + 2Na]+ species for each dipeptide.

P‐101: Degradation Analysis of OLED Panels by Laser Desorption/Ionization Time‐of‐Flight Mass Spectrometry with Fine‐Focused Imaging System

Degradation of the organic light‐emitting diode (OLED) panels was analyzed utilizing laser desorption/ionization time‐of‐flight mass spectrometry (LDI‐TOF‐MS). 349‐nm‐long UV laser with beam diameter of 5 µm was directly irradiated on the OLED panels to evaluate the change of mass spectra after thermal degradation. The mass to charge ratio was visualized by utilizing our imaging system with measurement speed of 30 µm2/s. The imaging technique helps us intuitively understand the change of material properties with area dependence on the panels.

Polyacrylonitrile-based carbon nanofibers as a matrix for laser desorption/ionization time-of-flight mass spectrometric analysis of small molecules under both positive and negative ionization modes.

Carbon fiber (CNF), prepared by carbonization of electrospun polyacrylonitrile (PAN) fibers, is systematically investigated as a mediator to replace conventional organic matrices for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). CNF exhibits a high salt tolerance, sensitivity, and resolution for organic matrix-free laser desorption/ionization time-of-flight mass spectrometry (LDI-MS) analysis of various analytes under both positive and negative ionization modes. Especially, saccharides, a neutral molecule having low negative ionization efficiency, are successfully detected with CNF. Taken together, this study clearly demonstrates CNF is a promising material to develop an efficient and universal platform for LDI-MS analysis regardless of preferential ionization modes of analytes. Graphical abstract.

Exfoliated MXene as a mediator for efficient laser desorption/ionization mass spectrometry analysis of various analytes

The exfoliated MXene (e-MXene) is systematically investigated as a mediator for laser desorption/ionization time-of-flight mass spectrometry (LDI-MS) analysis. Whereas un-exfoliated MXene has no activity for LDI-MS analysis, the e-MXene presents a high resolution, salt-tolerance and efficiency for LDI-MS analysis of various small molecules regardless of their polarity, aromaticity and molecular weight owing to its physicochemical properties such as high laser energy absorption, electrical conductivity and photothermal conversion. Based on our findings, it is clearly confirmed that e-MXene is a promising material for the development of an efficient platform for LDI-MS analysis of small molecules.

Nanostructured TiO2 Materials for Analysis of Gout-Related Crystals Using Laser Desorption/Ionization Time-of-Flight (LDI-ToF) Mass Spectrometry

Crystals of monosodium urate monohydrate (MSU) and calcium pyrophosphate dihydrate (CPPD) are known to induce arthropathic diseases called gout and pseudogout, respectively. These crystals are deposited in various joints or tissues, causing severe pain. Correct identification of crystals is crucial for the appropriate treatment of gout and pseudogout, which exhibit very similar symptoms. Herein, a novel approach of laser desorption/ionization time-of-flight (LDI-ToF) mass spectrometry (MS) was introduced to analyze MSU and CPPD crystals with three different types of nanostructured TiO2 materials including TiO2 nanoparticles (P25), TiO2 nanowires synthesized from wet-corrosion method, and the mixture of P25 and TiO2 nanowires (P25/TiO2 nanowires) as inorganic solid matrices. Furthermore, the feasibility of LDI-ToF MS based on these TiO2 nanostructures for the analysis of the two arthropathy-related crystals was tested using spiked samples in synovial fluid at known crystal concentrations. The mass analysis results of MSU and CPPD crystals demonstrated that (1) the electrostatic interaction between analytes and solid matrices was key for the analyte ionization and (2) LDI-ToF MS with nanostructured TiO2 materials has the potential to be a practical approach for the diagnosis of gout and pseudogout.

The Effect of Oxidative Debris on the Laser Desorption/Ionization Efficiency of Graphene Oxide Derivatives for Mass Spectrometric Analysis of Small Molecules and Synthetic Polymers.

The influence of oxidative debris (OD) on laser desorption/ionization time of flight mass spectrometry (LDI-TOF-MS) analysis using graphene oxide (GO) derivatives was systematically investigated. Specifically, the effects on LDI-TOF-MS analysis of small molecules and synthetic polymers were highlighted. The analytical efficiency of GO was significantly enhanced by removing OD from its surface and the working molecular weight range of GO was considerably extended for analysis of synthetic polymers and small molecules.

Laser desorption/ionization mass spectrometry-based compositional analysis of Au–Ag nanoplates synthesized by galvanic replacement and their application for small molecule analysis

This paper demonstrates that laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) can be utilized to analyze the relative atomic composition and photothermal conversion properties of Au–Ag alloy nanoplates synthesized by galvanic replacement reactions. Using Au–Ag alloy nanoplates with various shapes, it is found that the porous structures of the nanoplates affect their photothermal conversion efficiency more than their laser energy absorption capacity does. Based on these findings, the optimized Au–Ag alloy nanoplates can be applied to LDI-TOF-MS of small molecules.

Matrix-Incorporated Polydopamine Layer as a Simple, Efficient, and Universal Coating for Laser Desorption/Ionization Time-of-Flight Mass Spectrometric Analysis.

Self-oxidative copolymerization of dopamine with α-cyano-4-hydroxycinnamic acid (CHCA) provides an efficient and multifunctional platform for laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) analysis. The polydopamine coating layer embedded with the CHCA matrix can be readily formed on nanomaterials and solid substrates without additional surface treatments to generate an efficient LDI-TOF-MS platform for the analysis of small molecules as well as synthetic polymers. This coating can be further functionalized with specific ligands for target enrichment from complex biological media, providing analyte capture for subsequent LDI-TOF-MS analysis.

TiO2 Nanowires from Wet-Corrosion Synthesis for Peptide Sequencing Using Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

In this work, TiO2 nanowires synthesized from a wet-corrosion process were presented for peptide sequencing by photocatalytic reaction with UV radiation. For the photocatalytic decomposition of peptides, the peptide sample was dropped on a target plate containing synthesized TiO2 nanowire zones and UV-irradiated. Subsequently, the target plate was analyzed by laser desorption/ionization time-of-flight (LDI-TOF) mass spectrometry using the synthesized TiO2 nanowires as a solid matrix. The feasibility of peptide sequencing based on the photocatalytic reaction with the synthesized TiO2 nanowires was demonstrated using six types of peptides GHP9 (G1-H-P-Q-G2-K1-K2-K3-K4, 1006.59 Da), BPA-1(K1-S1-L-E-N-S2-Y-G1-G2-G3-K2-K3-K4, 1394.74 Da), PreS1(F1-G-A-N1-S-N2-N3-P1-D1-W-D2-F2-N4-P2-N5, 1707.68 Da), HPQ peptide-1 (G-Y-H-P-Q-R-K, 884.45 Da), HPQ peptide-2 (K-R-H-P-Q-Y-G, 884.45 Da), and HPQ peptide-3 (R-Y-H-P-Q-G-K, 884.45 Da). The identification of three different peptides with the same molecular weight was also demonstrated by using the synthesized TiO2 nanowires for their photocatalytic decomposition as well as for LDI-TOF mass spectrometry as a solid-matrix.

The influence of oxidative debris on the fragmentation and laser desorption/ionization process of graphene oxide derivatives

The influence of oxidative debris on laser desorption/ionization time of flight mass spectrometry (LDI-TOF-MS) analysis by using graphene oxide as a matrix was investigated to reveal its role in LDI process.

Size exclusion chromatography of lignin: The mechanistic aspects and elimination of undesired secondary interactions

Characterization of lignin and its degradation products, more specifically determination of their molecular weight (MW) distribution, is essential for assessment and applications of these potentially renewable phenolics. Several representative gel filtration and gel permeation systems were evaluated in this work focusing on understanding of undesired secondary non-SEC interactions while utilizing four sets of commercially available polymeric standards as well as low-MW lignin model compounds including diarene standards synthesized in-house. The gel permeation column with a nonpolar highly cross-linked porous polystyrene/divinylbenzene-based stationary phase provided the most effective separation by MW for both low and high MW model compounds. Notably, the column with a higher pore and lower particle size provided a better resolution towards polymeric standards, even though the particle size effect was downplayed in the earlier SEC studies of lignin. For two other evaluated gel filtration and gel permeation columns, the separation was strongly affected by functionalities of the analytes and correlated with the compounds’ pKa rather than MW. We showed that the separation on the stationary phases featuring polar hydroxyl groups led to specific column-analyte secondary interactions, perhaps based on their hydrogen bonding with lignin. Further, the SEC column evaluation yielded similar results with two sets of chemically different standards. This setup may be used as a general approach to selecting an applicable column for lignin SEC analysis. We confirmed the obtained results with a different independent method implementing a novel approach for lignin number-average MW (Mn) calculation based on laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) data. The determined Mn corroborated the SEC results.

Peculiarities of Pyrolysis of Hydrolytic Lignin in Dispersed Gas Phase and in Solid State

The unique decomposition pathways of hydrolytic lignin (HL) dissolved in an acetone/water mixture (9:1) and dispersed by a droplet evaporation technique under nitrogen gas flow has been investigated in a conventional reactor at atmospheric condition, a temperature region of 400–550 °C, and a residence time of 0.12 s. The results validate the fact that dispersion of the lignin into the gas phase by decreasing the sample size (as well as “minimizing the char area to avoid catalytic contact” of molecular products/radicals with the surface) may open new perspectives in understanding the chemistry of the depolymerization of lignin. Using Laser Desorption Ionization-Time of Flight-Mass Spectrometry (LDI-TOF-MS) the intrinsic ion m/z = 550, as the major MS peak from fresh HL dissolved in an acetone/water mixture before pyrolysis, was detected. Surprisingly, the expected phenolic compounds after pyrolysis were in trace amounts at less than 15% conversion of lignin. Instead, oligomeric intermediate substances with...

Effect of ecosystem type and fire on chemistry of WEOM as measured by LDI-TOF-MS and NMR

Soil organic matter (SOM) and its water-soluble components play an important role in terrestrial carbon cycling and associated ecosystem functions. Chemically, they are complex mixtures of organic compounds derived from decomposing plant material, microbial residues, as well as root exudates, and soil biota. To test the effect of the ecosystem type (forest and grassland) and fires events on the chemistry of dissolved organic matter (DOM), we applied a combination of laser-desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) and 2D (1H and 13C) nuclear magnetic resonance (NMR) spectroscopy to water-extractable organic matter (WEOM) from a range of top soil samples. The aim was to assess the suitability of LDI-TOF-MS for the rapid characterization of WEOM. Therefore, we evaluated the effects of sample (pH and dilution) conditions and use of positive or negative reflector mode to identify the conditions under which LDI-TOF-MS best distinguished between WEOM from different sources. Thirty-six samples were measured with both analytical techniques and their chemical patterns were statistically evaluated to distinguish firstly the effect of the type of ecosystem (forest versus grassland) on WEOM characteristics, and secondly the impact of fire on the chemical composition of WEOM. The nonmetric multidimensional scaling (NMDS) analysis of the most suitable experimental LDI-TOF-MS conditions showed a clear separation between the type of vegetation and fire-induced changes, mostly reflecting the presence of poly(ethylene glycol) in grassland soils. Discrimination among WEOM from different vegetation types was preserved in the fire treated samples. The calculation of the relative abundance of certain functional structures in the WEOM samples revealed a common composition of forest and grassland WEOM, with polysaccharides and proteins making up to 60%. The compositional impact of forest fire on WEOM was more pronounced compared to the one of grassland, leading to a decline in the main components, and an increase in amino-sugars, fatty acids, and sterols. The recorded 1H NMR and heteronuclear single quantum coherence (HSQC) spectra showed a decrease of the carbohydrate signal in WEOM from fire-treated samples, which was more pronounced in forest than in grassland soils.

Structural Characterization of Large Polycyclic Aromatic Hydrocarbons. Part 2: Solvent-Separated Fractions of Coal Tar Pitch and Naphthalene-Derived Pitch

Complex polycyclic aromatic hydrocarbon (PAH) mixtures separated from a coal tar pitch (CP) and naphthalene pitch (NP) by sequential extraction with heptane and toluene were characterized in detail by applying a multiarray analytical approach. Gas chromatography–mass spectrometry (GC-MS), size exclusion chromatography (SEC), laser desorption ionization-time-of-flight mass spectrometry (LDI-TOFMS), and thermogravimetry (TG) were used to relate the volatility and coking yield of pitch components to their solubility and molecular weight distribution. Spectroscopic analysis, including infrared (IR), ultraviolet–visible (UV–vis), and fluorescence spectroscopy, proved to be useful for measuring specific features of aromatic systems, such as the aromatic content, degree of aliphatic substitution, and size distribution of PAHs of different molecular weights. In particular, it has been shown that the spectroscopic analysis is an essential tool for characterizing very large PAH systems concentrated in the pitch tol...