Zirconium silicate assisted removal of residual proteins after organic solvent deproteinization of human plasma,enhancing the stability of the LC–ESI-MS response for the bioanalysis of small molecules

An efficient blood plasma clean-up method was developed, where methanol protein precipitation was applied, followed by zirconium silicate assisted exclusion of residual proteins. A strong binding of zirconium (IV) silicate to the proteins enabled the elimination of remaining proteins after solvent deproteinization through a rapid solid-phase extraction (SPE) procedure. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF MS) was used for monitoring the proteins during clean-up practice applied to human plasma samples. The proteins were quantified by colorimetric detection using the bicinchoninic acid (BCA) assay. The presented analytical strategy resulted in the depletion of >99.6% proteins from human plasma samples. Furthermore, high-performance liquid chromatography hyphenated to diode-array and electrospray ionization mass spectrometric detection (HPLC–DAD/ESI MS) was applied for qualitative and quantitative analysis of the caffeoylquinic acids (CQAs) and their metabolites in human plasma. The procedure demonstrated high recoveries for the standard compounds spiked at different concentrations. Cynarin and chlorogenic acid were recovered in the range of 81–86% and 78–83%, respectively. Caffeic acid was extracted in the excess of 89–92%, while ferulic acid and dihydroxyhydrocinnamic acid showed a recovery of 87–91% and 92–95%, respectively. The method was partially validated in accordance with FDA-Industry Guidelines for Bioanalytical Method Validation (2001). The presented scheme improves the clean-up efficacy of the methanol deproteinization, significantly reduces the matrix effects and provides a great analytical tool for the isolation of small molecules from human plasma.     

Vibrational and orientational dynamics of water in aqueous hydroxide solutions

We report the vibrational and orientational dynamics of water molecules in isotopically diluted NaOH and NaOD solutions using polarization-resolved femtosecond vibrational spectroscopy and terahertz time-domain dielectric relaxation measurements. We observe a speed-up of the vibrational relaxation of the O-D stretching vibration of HDO molecules outside the first hydration shell of OH(-) from 1.7 ± 0.2 ps for neat water to 1.0 ± 0.2 ps for a solution of 5 M NaOH in HDO:H(2)O. For the O-H vibration of HDO molecules outside the first hydration shell of OD(-), we observe a similar speed-up from 750 ± 50 fs to 600 ± 50 fs for a solution of 6 M NaOD in HDO:D(2)O. The acceleration of the decay is assigned to fluctuations in the energy levels of the HDO molecules due to charge transfer events and charge fluctuations. The reorientation dynamics of water molecules outside the first hydration shell are observed to show the same time constant of 2.5 ± 0.2 ps as in bulk liquid water, indicating that there is no long range effect of the hydroxide ion on the hydrogen-bond structure of liquid water. The terahertz dielectric relaxation experiments show that the transfer of the hydroxide ion through liquid water involves the simultaneous motion of ~7 surrounding water molecules, considerably less than previously reported for the proton.     

Preparation of polymer based sorbents for solid phase extraction of polyphenolic compounds

This article discusses the preparation of different polymeric sorbents for solid phase extraction. Various monomers like acrylamide, methacrylic acid and 4-vinylpyridine (VP), cross-linkers such as divinylbenzene (DVB) and ethyleneglycoldimethacrylate (EDMA), porogens like tetrahydrofuran (THF) and dimethylsulphoxide (DMSO) / acetonitrile (ACN) with different ratios were investigated in order to optimize recoveries. Resulting polymers were characterized through scanning electron microscope (SEM) and compared with Oasis HLB (Waters, MA, USA) and Strata-X (Phenomenex, Torrance, USA) on the basis of extraction performance, recovery efficiency and loading capacity. Sample applied was a mixture of flavonoid standards (rutin, myricetin, luteolin, quercetin, apigenin and kaempferol). HPLC hyphenated with PDA was used for the analysis of samples. Results showed that among the prepared SPE materials, 4-VP-co-EDMA produced best results. Comparison of the produced polymers with of Oasis HLB and Strata-X resulted in comparable efficiencies; especially the polymer 4-VP-co-EDMA gave almost similar results for all analytes to those of commercially available SPE materials. A general trend of decrease in retention efficiency with increase in polarity has been observed in both synthesized and already available SPE materials. The newly synthesized polymeric materials can be employed as SPE sorbents for efficient extraction of polyphenolic compounds especially for flavonoid aglycons.     

Toeplitz liftings of Hankel forms bounded by non-Toeplitz norms

The Sz.Nagy-Foias commutant theorem is concerned with operators that commute with the compression of a given unitary operator, and it is natural to ask what can be said in the case of the compression of a nonunitary operator. Since the Sz.Nagy-Foias theorem was shown to be logically equivalent to a lifting theorem of Hankel forms subordinated to a pair of positive Toeplitz forms, another formulation of the question is: What can be said about the Toeplitz extension of a Hankel form subordinated to a pair of positive but non-Toeplitz forms? Here we give some answers to this question, relating it to unitary extensions in Krein spaces and to scattering systems whose evolution operator is unitary only with respect to an indefinite metric. Integral representations can be given in the case of the Nehari theorem, where the Grothendieck inequality plays a role.     

Analytical determination of organic acids formed during hydrothermal and organosolv degradation of lignocellulosic biomass

Summary The present study deals with the isotachophoretic and the ion chromatographic analysis of organic acids found in hydrolysates of lignocellulosic biomass. The samples were pretreated by means of ultrafiltration to increase the reproducibility of the measurements. The qualitative and quantitative analysis of the fractions obtained during hydrothermal and organosolv degradations of wheat straw allowed a comparison of the rate and amount of organic acids formed (formic acid, glycolic acid, lactic acid, acetic acid). Isotachophoresis facilitates research on the reaction mechanisms underlying the hydrolysis of biomass.

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Analyse der durch Hydrothermolyse und Organosolv-Aufschluß von lignocellulosehaltiger Biomasse gebildeten organischen Säuren

     

Quadrupole interaction of8Li and9Li in LiNbO3 and the quadrupole moment of9Li

The quadrupole interaction of nuclear spin polarized⁸Li (I=2) and⁹Li (I=3/2) in LiNbO₃ has been studied at room temperature. The polarization was achieved by optical pumping of a fast atomic beam with circularly polarized laser light. The atoms were implanted into a hexagonal LiNbO₃ single crystal and the quadrupole splitting ofβ-NMR spectra was measured. A ratio of ¦Q(⁹Li)/Q(⁸Li)¦=0.88(4) for the nuclear quadrupole moments was deduced, yielding a new value of ¦Q(⁹Li)¦=25.3 (9) mb for the quadrupole moment of⁹Li.     

Capillary electrophoretic analysis of flavonoids.

Combining the effects of electrophoresis and electroendosmosis, flavonoids were separated in less than ten minutes in a fused silica capillary tube with a borate buffer adjusted to pH 10. An increase in the concentration of borate from 0.1 to 0.2 M resulted in longer migration times due to a decrease in electroosmotic flow, but also in improved selectivity and higher resolution of flavonoids. The calibration curve of rutin showed a detection limit of 0.02 mg/mL and linearity over its pharmaceutical concentration range. Using an internal standard of known concentration, the content of rutin in a methanolic extract of Sambuci flos could be determined with a coefficient of variation as small as 3.8% by the molar ratio-peak area ratio method.