Quasi-classical rate constants for the inelastic process O2(υi≫ 1) + O2 → O2(υf) + O2

Rate constants have been calculated using quasi-classical trajectories (QCT) for the vibrational relaxation of highly excited O₂:O₂(X³Σ?,v_i) + O₂(X³Σ?,0) → O₂(X³Σ?,v_f) + O₂(X³Σ?) with 22 ≤v_i≤28. The present full-dimensional QCT results agree very well with recent quantum reduced dimensionality calculations, giving further support to the hypothesis that the observed experimental jump in depletion rates would be due partially to enhanced vibrational relaxation.     

Copper(I) complexes with trispyrazolylmethane ligands: synthesis, characterization, and catalytic activity in cross-coupling reactions

Three novel Cu(I) complexes bearing tris(pyrazolyl)methane ligands, Tpm(x), have been prepared from reactions of equimolar amounts of CuI and the ligands Tpm, (HC(pz)(3)), Tpm*, (HC(3,5-Me(2)-pz)(3)), and Tpm(Ms), (HC(3-Ms-pz)(3)). X-ray diffraction studies have shown that the Tpm and Tpm(Ms) derivatives exhibit a 2:1 Cu:ligand ratio, whereas the Tpm* complex is a mononuclear species in nature. The latter has been employed as a precatalyst in the arylation of amides and aromatic thiols with good activity. The synthesis of a Tpm*Cu(I)-phthalimidate, a feasible intermediate in this catalytic process, has also been performed. Low temperature (1)H NMR studies in CDCl(3) have indicated that this complex exists in solution as a mixture of two, neutral and ionic forms. Conductivity measurements have reinforced this proposal, the ionic form predominating in a very polar solvent such as DMSO. The reaction of Tpm*Cu(I)-phthalimidate with iodobenzene afforded the expected C-N coupling product in 76% yield accounting for its role as an intermediate in this transformation.     

Selective opening of nanoscopic capped mesoporous inorganic materials with nerve agent simulants; an application to design chromo-fluorogenic probes

A hybrid nanoscopic capped mesoporous material, that is selectively opened in the presence of nerve agent simulants, has been prepared and used as a probe for the chromo-fluorogenic detection of these chemicals.     

Identification of bioactive peptides in hypoallergenic infant milk formulas by capillary electrophoresis-mass spectrometry

In this study, we use capillary electrophoresis-mass spectrometry (CE-MS) for the identification of bioactive peptides in hypoallergenic infant milk formulas (IF), which are complex bovine milk protein hydrolysates. A sample clean-up pretreatment with a citrate buffer containing dithiothreitol and urea followed by solid-phase extraction (SPE) with different reversed-phase commercial cartridges was investigated to achieve optimum detection sensitivity in CE-MS. SPE with C18, StrataX and Oasis HLB cartridges allowed detection of the largest number of low molecular mass components, but combination of C18 and StrataX results was enough to achieve an excellent coverage of the studied IF. The monoisotopic molecular mass values of the low molecular mass components obtained by capillary electrophoresis ion-trap mass spectrometry (CE-IT-MS) allowed the tentative identification of nine bioactive sequences. Only the identification of five of them could be confirmed when accurate mass measurements were performed by capillary electrophoresis time-of-flight mass spectrometry (CE-TOF-MS), namely LKP, IPY, ALPM, PGPIHN and VAGTWY, which were reported to present angiotensin-converting enzyme (ACE) inhibitory and antimicrobial activity (only VAGTWY).     

Possibilities and limitations of the sequential injection chromatography technique for the determination of anticoccidial agents in water, pharmaceutical formulations and feed

This paper explores the potential of applying reversed-phase sequential injection chromatography (SIC) to determine the anticoccidial agents Lasalocid and Toltrazuril in various matrices including ground water, pharmaceutical formulations and feed. SIC was performed by connecting a 25 × 4.6 mm monolithic C18 column to a 2 m long pathlength capillary flow cell, where the usage of a flow cell lowers the detection limit compared to a conventional short-distance flow cell, providing a simple detection system for these two compounds which are initially poorly UV absorbents.The proposed set-up provides a high injection throughput of 12 h^{− 1}, as well as a limit of detection of 0.019 and 0.010 mg/L for Toltrazuril and Lasalocid, respectively. The repeatabilities obtained (n = 10) were lower than 2% and 4% for Toltrazuril and Lasalocid, respectively.     

Relative quantitation of glycosylation variants by stable isotope labeling of enzymatically released N-glycans using [12C]/[13C] aniline and ZIC-HILIC-ESI-TOF-MS

Glycan reductive isotope labeling (GRIL) using [¹²C]- and [¹³C]-coded aniline was used for relative quantitation of N-glycans. In a first step, the labeling method by reductive amination was optimized for this reagent. It could be demonstrated that selecting aniline as limiting reactant and using the reductant in excess is critical for achieving high derivatization yields (over 95 %) and good reproducibility (relative standard deviations ～1–5 % for major and ～5–10 % for minor N-glycans). In a second step, zwitterionic–hydrophilic interaction liquid chromatography in capillary columns coupled to electrospray mass spectrometry with time-of-flight analyzer (μZIC-HILIC-ESI-TOF-MS) was applied for the analysis of labeled N-glycans released from intact glycoproteins. Ovalbumin, bovine α₁-acid-glycoprotein and bovine fetuin were used as test glycoproteins to establish and evaluate the methodology. Excellent separation of isomeric N-glycans and reproducible quantitation via the extracted ion chromatograms indicate a great potential of the proposed methodology for glycoproteomic analysis and for reliable relative quantitation of glycosylation variants in biological samples.     

Improved spectrophotometric determination of paraquat in drinking waters exploiting a Multisyringe liquid core waveguide system

A novel Multisyringe flow injection analysis (MSFIA) system combined with a 200 cm long pathlength liquid core waveguide (LCW) has been developed enabling for the first time the sensitive spectrophotometric determination at μg L⁻¹ levels of the herbicide paraquat (Pq²⁺) in drinking waters. The proposed system is a simple, economic and fast alternative for obtaining the first evidence of paraquat pollution prior the use of more complex instrumental techniques.The proposed methodology is based on the production of a blue free radical by reaction of Pq²⁺ with ascorbic acid (partially oxidized with potassium iodate) in basic medium. Limits of detection and quantification as low as 0.7 and 2.3 μg L⁻¹, were obtained respectively. The working range is linear up to a concentration of 250 μg L⁻¹ of Pq²⁺. The injection throughput of the proposed method is 34 h⁻¹. The results obtained with the LCW are compared with those using a conventional 1 cm flow cell. The automation of standard addition procedures has been studied and implemented for samples causing matrix effects. Finally the proposed system has been applied to the determination of paraquat in drinking water samples.