Effect of method of ion preparation on low-energy collision-induced dissociation mass spectra

The collision-induced dissociation (CID) mass spectra of protonated cocaine and protonated heroin have been measured using a triple quadrupole mass spectrometer at 50 eV ion/neutral collision energy for protonated molecules prepared by different protonating agents. The CID mass spectra of protonated cocaine using H⁺(H₂O)_n, H⁺(NH₃)_n and H⁺((CH₃)₂NH)_n as protonating agents are essentially identical and it is concluded that, regardless of the initial site of protonation, the fragmentation reactions occurring on collisional activation are identical. By contrast, protonated heorin prepared with H⁺(H₂O)_n and H⁺(NH₃)_n as protonating agents show substantial differences. That formed by reaction of H⁺(H₂O)_n shows a much more abundant peak corresponding to loss of CH₃CO₂H. From a comparison with model compounds, and from a consideration of the three-dimensional structure of heroin, it is concluded that with H⁺(H₂O)_n as protonating agent significant protonation occurs at the acetate group attached to the alicyclic ring, leading to acetic acid loss on collisional activation, but that reaction of H⁺(NH₃)_n leads to protonation at the nitrogen function. The proton attached to nitrogen cannot interact with the acetate group and, consequently, the probability of loss of acetic acid on collislional activation is greatly reduced.     

Generic applications of 13C‐detected NMR diffusion to formulated systems with suppression of thermal convection induced by proton decoupling

Fast and effective structural/compositional analysis on formulated systems represents one of the major challenges encountered in analytical science. ¹³C‐detected diffusion represents a promising tool to tackle the aforementioned challenges, particularly in industry. Toward exploring the generic applications of ¹³C‐detected diffusion, thermal convection induced by ¹H decoupling has been identified as a key factor that resulted in significantly reduced resolution in the diffusion dimension. Optimization of experimental parameters and utilization of double‐stimulated echo‐based pulse sequence both can effectively suppress the thermal convection caused by the ¹H decoupling, the success of which allows robust and generic applications of ¹³C‐detected diffusion to systems from mixtures of small molecules, polymer blends, and copolymers to actual complex formulated systems. The method is particularly powerful in differentiating small molecules from polymers, polymer blends from copolymers, and end‐group analysis. Copyright © 2016 John Wiley & Sons, Ltd.     

Arraying Cell Cultures Using PEG‐DMA Micromolding in Standard Culture Dishes

A robust and effortless procedure is presented, which allows for the microstructuring of standard cell culture dishes. Cell adhesion and proliferation are controlled by three‐dimensional poly(ethylene glycol)‐dimethacrylate (PEG‐DMA) microstructures. The spacing between microwells can be extended to millimeter size in order to enable the combination with robotic workstations. Cell arrays of microcolonies can be studied under boundary‐free growth conditions by lift‐off of the PEG‐DMA layer in which the growth rate is accessible via the evolution of patch areas. Alternatively, PEG‐DMA stencils can be used as templates for plasma‐induced patterning.

     

Analysis of egg-based model wall paintings by use of an innovative combined dot-ELISA and UPLC-based approach

The chemical analysis of egg-based wall paintings—the mezzo fresco technique—is an interesting topic in the characterisation of organic binders. A revised procedure for a dot-enzyme-linked immunosorbent assay (dot-ELISA) able to detect protein components of egg-based wall paintings is reported. In the new dot-ELISA procedure we succeeded in maximizing the staining colour by adjusting the temperature during the staining reaction. Quantification of the colour intensity by visible reflectance spectroscopy resulted in a straight line plot of protein concentration against reflectance in the wavelength range 380–780 nm. The modified dot-ELISA procedure is proposed as a semi-quantitative analytical method for characterisation of protein binders in egg-based paintings. To evaluate its performance, the method was first applied to standard samples (ovalbumin, whole egg, egg white), then to model specimens, and finally to real samples (Giotto’s wall paintings). Moreover, amino acid analysis performed by innovative ultra-performance liquid chromatography was applied both to standards and to model samples and the results were compared with those from the dot-ELISA tests. In particular, after protein hydrolysis (24 h, 114 °C, 6 mol L^?1 HCl) of the samples, amino acid derivatization by use of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate enabled reproducible analysis of amino acids. This UPLC amino acid analysis was rapid and reproducible and was applied for the first time to egg-based paintings. Because the painting technique involved the use of egg-based tempera on fresh lime-based mortar, the study enabled investigation of the effect of the alkaline environment on egg-protein detection by both methods.

Use of apodization in quantitative spectroscopy

Apodization, which is a tool frequently used for cosmetic representation and efficient modeling of a spectrum, is now also adopted in techniques for the quantitative retrieval of parameters from observed spectra. Whether apodization can help in quantitative spectroscopy is the subject of debate in the literature. We find that, when the considered spectral range is wide enough to accurately model the instrument line shape, the same results can be obtained with and without apodization of the spectrum. However, when a truncation error is introduced by the limited extension of the modeled spectral interval, apodization can efficiently reduce this error. Therefore it is possible to save computing time by using apodization.     

Qualitative and quantitative analysis of new alkyl amide arginine surfactants by high-performance liquid chromatography and capillary electrophoresis.

A protocol for the qualitative and quantitative analysis of novel arginine-based cationic surfactants using HPLC and CE was studied and compared. The optimization of the analytical conditions was carried out through a systematic variation of the experimental parameters such as mobile phase, eluent conditions, ion pairing and amount of sample for HPLC, and type of buffer, ion strength, type and amount of organic solvent, sample injection time, applied voltage and column washing and conditioning for CE.     

Simultaneous determination of benzydamine hydrochloride and five impurities in an oral collutory as a pharmaceutical formulation by high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method for the determination of benzydamine hydrochloride and its impurities 3-dimethylaminopropyl 2-benzylaminobenzoate, 3-dimethylaminopropyl-2-aminobenzoate,1-benzyl-1H-indazol-3-ol, 1-benzyl-2-(3-dimethylaminopropyl)-1,2-dihydro-3H-indazol-3-one, and 1-benzyl-3-(3-(3-dimethylaminopropyl)-3-methylamino)propoxy-(1)H-indazole in a collutory formulation is developed. The separation is carried out on a Gemini C(18) (250 × 4.6 mm, 5 μm) column using acetonitrile-methanol-ammonium carbonate buffer (10 mM; pH 10.5) (37.5:37.5:25, v/v/v) as mobile phase at a flow rate of 1.0 mL/min, column temperature 30°C, and UV detection at 218 nm. Famotidine is used as an internal standard. The total run-time is less than 15 min. The analytical curves present coefficients of correlation greater than 0.99, and detection limits are calculated for all analytes. Excellent accuracy and precision are obtained for benzydamine hydrochloride. Recoveries vary from 98.25 to 102.8%, and intra- and inter-day precisions, calculated as the percent relative standard deviation, are lower than 2.2%. Specificity and robustness for benzydamine hydrochloride are also determined. The method allows the quantitative determination of benzydamine hydrochloride and its impurities, and it is suitable for routine analysis in quality control laboratories.