Rapid Quadrupole-Time-of-Flight Mass Spectrometry Method Quantifies Oxygen-Rich Lignin Compound in Complex Mixtures

Complex mixture analysis is a costly and time-consuming task facing researchers with foci as varied as food science and fuel analysis. When faced with the task of quantifying oxygen-rich bio-oil molecules in a complex diesel mixture, we asked whether complex mixtures could be qualitatively and quantitatively analyzed on a single mass spectrometer with mid-range resolving power without the use of lengthy separations. To answer this question, we developed and evaluated a quantitation method that eliminated chromatography steps and expanded the use of quadrupole-time-of-flight mass spectrometry from primarily qualitative to quantitative as well. To account for mixture complexity, the method employed an ionization dopant, targeted tandem mass spectrometry, and an internal standard. This combination of three techniques achieved reliable quantitation of oxygen-rich eugenol in diesel from 300 to 2500 ng/mL with sufficient linearity (R² = 0.97 ± 0.01) and excellent accuracy (percent error = 0% ± 5). To understand the limitations of the method, it was compared to quantitation attained on a triple quadrupole mass spectrometer, the gold standard for quantitation. The triple quadrupole quantified eugenol from 50 to 2500 ng/mL with stronger linearity (R² = 0.996 ± 0.003) than the quadrupole-time-of-flight and comparable accuracy (percent error = 4% ± 5). This demonstrates that a quadrupole-time-of-flight can be used for not only qualitative analysis but also targeted quantitation of oxygen-rich lignin molecules in complex mixtures without extensive sample preparation. The rapid and cost-effective method presented here offers new possibilities for bio-oil research, including: (1) allowing for bio-oil studies that demand repetitive analysis as process parameters are changed and (2) making this research accessible to more laboratories.

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Regioselective ion-molecule reactions for the mass spectrometric differentiation of protonated isomeric aromatic diamines

A mass spectrometric method utilizing regioselective ion-molecule reactions has been developed for the differentiation of protonated isomeric aromatic diamines in FT-ICR, linear quadrupole ion trap and triple quadrupole mass spectrometers.     

Gas-phase reactivity of aromatic sigma,sigma-biradicals toward dinucleoside phosphates

In order to improve the understanding of the interactions of aromatic sigma,sigma-biradicals with DNA, the reactivity of three isomeric sigma,sigma-biradicals toward four dinucleoside phosphates was studied in a mass spectrometer. The dinucleoside phosphates were evaporated into the mass spectrometer by using laser-induced acoustic desorption (LIAD). The results demonstrate that the structure of the sigma,sigma-biradical and the base sequence of the dinucleoside phosphate can have a major influence on these reactions.     

Comparison of Functional Group Selective Ion–Molecule Reactions of Trimethyl Borate in Different Ion Trap Mass Spectrometers

We report here a comparison of the use of diagnostic ion–molecule reactions for the identification of oxygen-containing functional groups in Fourier-transform ion cyclotron resonance (FTICR) and linear quadrupole ion trap (LQIT) mass spectrometers. The ultimate goal of this research is to be able to identify functionalities in previously unknown analytes by using many different types of mass spectrometers. Previous work has focused on the reactions of various boron reagents with protonated oxygen-containing analytes in FTICR mass spectrometers. By using a LQIT modified to allow the introduction of neutral reagents into the helium buffer gas, this methodology has been successfully implemented to this type of an ion trap instrument. The products obtained from the reactions of trimethyl borate (TMB) with various protonated analytes are compared for the two instruments. Finally, the ability to integrate these reactions into LC-MS experiments on the LQIT is demonstrated.     

Reactivity Controlling Factors for an Aromatic Carbon‐Centered σ,σ,σ‐Triradical: The 4,5,8‐Tridehydroisoquinolinium Ion

The chemical properties of the 4,5,8‐tridehydroisoquinolinium ion (doublet ground state) and related mono‐ and biradicals were examined in the gas phase in a dual‐cell Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectrometer. The triradical abstracted three hydrogen atoms in a consecutive manner from tetrahydrofuran (THF) and cyclohexane molecules; this demonstrates the presence of three reactive radical sites in this molecule. The high (calculated) electron affinity (EA=6.06 eV) at the radical sites makes the triradical more reactive than two related monoradicals, the 5‐ and 8‐dehydroisoquinolinium ions (EA=4.87 and 5.06 eV, respectively), the reactivity of which is controlled predominantly by polar effects. Calculated triradical stabilization energies predict that the most reactive radical site in the triradical is not position C4, as expected based on the high EA of this radical site, but instead position C5. The latter radical site actually destabilizes the 4,8‐biradical moiety, which is singlet coupled. Indeed, experimental reactivity studies show that the radical site at C5 reacts first. This explains why the triradical is not more reactive than the 4‐dehydroisoquinolinium ion because the C5 site is the intrinsically least reactive of the three radical sites due to its low EA. Although both EA and spin–spin coupling play major roles in controlling the overall reactivity of the triradical, spin–spin coupling determines the relative reactivity of the three radical sites.     

Functional dye as a comonomer in a water‐soluble polymer

In many applications, a functional additive is blended into a polymer matrix to enhance its properties. However, when the polymer and functional additive are applied to a surface, the functional molecule may be easily lost. In favorable cases, it may be possible to incorporate the additive directly into the polymer as a comonomer. In this study, a functionalized polymer has been obtained through the combination of linking a photodynamic, antimicrobial dye, Rose Bengal, to vinyl benzyl chloride via etherification and then polymerizing this into a water‐soluble polymer using chain growth copolymerization. Characterization of the efficiency of synthesis, solubility of the final product, and singlet oxygen production rate has been performed. Dialysis was used to determine the extent of incorporation of the dye into the polymer. The chemical structure of the intermediate produced through etherification has been verified. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1594–1599     

Data-dependent neutral gain MS<Superscript>3</Superscript>: Toward automated identification of the N-Oxide functional group in drug metabolites

We report here an automated method for the identification of N-oxide functional groups in drug metabolites by using the combination of liquid chromatography/tandem mass spectrometry (LC/MS ⁿ ) based on ion-molecule reactions and collision-activated dissociation (CAD). Data-dependent acquisition, which has been readily utilized for metabolite characterization using CAD-based methods, is adapted for use with ion-molecule reaction-based tandem mass spectrometry by careful choice of select experimental parameters. Two different experiments utilizing ion-molecule reactions are demonstrated, data-dependent neutral gain MS³ and data-dependent neutral gain pseudo-MS³, both of which generate functional group selective mass spectral data in a single experiment and facilitate increased throughput in structural elucidation of unknown mixture components. Initial results have been generated by using an LC/MS ⁿ method based on ion-molecule reactions developed earlier for the identification of the N-oxide functional group in pharmaceutical samples, a notoriously difficult functional group to identify via CAD alone. Since commercial software and straightforward, external instrument modification are used, these experiments are readily adaptable to the industrial pharmaceutical laboratory.     

Steady vortical flow around a finite plate

An explicit solution for a layer of fluid with constant vorticitysurrounding a thin plate of finite length is obtained usingelementary conformal mapping methods. In the limit of largeplate length the behaviour of the solution near the ends ofthe plate tends to that of the previously known solution fora semi-infinite plate. Contour dynamics is used to investigatethe stability of the steady solutions.