Ionic liquid matrices for MALDI mass spectrometry of lignin

Analytical and Bioanalytical Chemistry - The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the study of lignin is still extremely limited due to its low...     

Solvatochromism and preferential solvation of <Emphasis Type="Italic">para</Emphasis>-derivatives of guaiacol in water-N,N-dimethylformamide mixtures

The influence of the composition of the water-N,N-dimethylformamide mixed solvent on the position of the B absorption band in UV spectra of 2-methoxyphenol, its para-substituted derivatives, and corresponding phenolate anions simulating base units of natural lignin is investigated. The data obtained are interpreted in terms of the model of preferential solvation. The preferential solvation parameters and compositions of the solvation shells are calculated.     

Structure and electric properties of BaCe0.77 ? xZrxGd0.2Cu0.03O3 ? δ

In the present work, samples with the composition of BaCe_{0.77 − x} Zr _x Gd_0.2Cu_0.03O_{3 − δ} (x = 0, 0.1…0.7, 0.77) were synthesized according to the standard solid state technique. The effect of zirconium oxide on the phase character, structure, and conductivity was studied using the methods of X-ray diffraction analysis, scanning electron microscopy, and four-probe method, accordingly. Stability of these materials in the flow of carbon dioxide was studied. The results show that introduction of zirconium oxide leads to preservation of a single-phase system (x ≤ 0.6), a decrease in the grain size, and an increase in stability in the CO₂ atmosphere.     

Protolytic properties of lignin in binary mixtures of water with aprotic solvents

Acid dissociation constants for three main types of phenol structural fragments of lignin in binary mixtures of water with N,N-dymethylformamide, dimethyl sulfoxide, and 1,4-dioxane were determined by spectrophotometric potentiometric titration. The effect of solvent on lignin protolytic properties was examined on the basis of the Kamlet-Taft principle of linear relationship of free solvation energies. It was found that nonspecific interactions with solvent make the dominating contribution to the effect of the medium.     

Solvent effect on the acidity constants of lignin-related phenols in water-acetone and water-1,4-dioxane binary mixtures within the Kamlet-Taft formalism

Multiparameter regression analysis combined with the principle of liner solvation energies relationship was applied to assess the solvent effect on the acidity of the lignin-related phenols in water-dioxane and water-acetone systems. The coefficients a, b, and s of the Kamlet-Taft equation were calculated taking into account the contributions of different types of solute-solvent interactions to the protolytic properties of the phenols of the guaiacol series.     

The Acidity and Solvation of Lignin-Related Phenols in Water—1,4-Dioxane Mixtures

The pK _a values were determined for 10 guaiacyl phenols by UV spectrophotometric and potentiometric titration in the water—dioxane binary system over the composition range 0–80% organic solvent. The differentiating action of the solvent and para-substituent effects on the acidity of guaiacol derivatives were analyzed. The dependences of acidity constants on the mixed solvent composition were interpreted using the preferential solvation model.     

Study of Lignin by Atmospheric Pressure Photoionization Orbitrap Mass Spectrometry: Effect of Spectral Resolution

Journal of Analytical Chemistry - Atmospheric pressure photoionization Orbitrap mass spectrometry is a promising tool for studying lignin. It ensures the detection of thousands of lignin oligomers...     

Carbon nanocoatings: A new approach to recording mass spectra of low-molecular compounds using surface-assisted laser desorption/ionization mass spectrometry

A simple and rapid approach to obtaining target plates for the investigation of low-molecularweight compounds by surface-assisted laser desorption/ionization (SALDI) mass spectrometry is proposed. It consists in the vacuum sputtering of a carbon layer with a thickness of about 50 nm onto a metal surface. The resulting coatings are characterized by homogeneity, hydrophobicity, and high mechanical strength, which eliminates a possibility of mass spectrometer contamination. A comparison of the SALDI mass spectra of test compounds recorded using conventional carbon materials and carbon nanocoatings demonstrates advantages of the last named materials, such as high spectral resolution and the absence of spectral interferences at low m/z values.     

Charge transfer in mixed proton, oxygen ion and electron solid oxide conductor

Analysis of the equivalent scheme of the mixed proton-oxygen ion-electron conductor (MPOEC) allowed to obtain relationships between parameters of the membrane (total conductivity and transfer numbers) and parameters of the charge and mass transfer through the membrane (partial ion and electron currents, the specific flux of hydrogen at the cathode membrane surface) under regime of electrochemical reforming. It was stated that presence of proton conductivity in addition to oxygen ion conductivity led to increase of total flux of produced hydrogen. However, under conditions typical for the electrochemical reforming of methane into hydrogen, the specific hydrogen flux is about four times lower in the case when the membrane has proton-electron conductivity than in the case when the membrane has oxygen ion-electron conductivity. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 – 18, 2004.