Application of synchronous fluorescence to parchment characterization

A nondestructive method for quantitative parchment characterization and sensitive indication of its deterioration stage was developed. Synchronous fluorescence (SF) measurements were applied for the first time to parchment samples. The method provides detailed spectral features, which are useful for parchment characterization. The discrimination of parchment samples into groups (modern, historical, and artificially aged) was successfully performed. The SF spectra could be resolved into specific fluorophores, which were related to the parchment condition. The spectral data indicate a continuous change in the collagen-to-gelatin ratio during the aging process. Depth-resolved synchronous fluorescence spectra were also measured. The data indicate that parchments possess a layered structure, and the dominant fluorophore in the upper layer is different from those in the lower layers. Layer-resolved profiling allows for quantifying the contribution of each fluorophore in each given layer. This way, significant differences between modern, artificially aged, and historical samples can be observed.     

Microbial screening methods for detection of antibiotic residues in slaughter animals

Monitoring of food products from animal origin for the presence of antimicrobial residues is preferably done using microbial screening methods because of their high cost-effectiveness. Traditionally applied methods fail to detect the maximum residue limits which were established when EU Council Regulation 2377/90 came into effect. Consequently, during the last decade this has led to the development of improved microbial screening methods. This review provides an overview of the efforts expended to bring antibiotic screening methods into compliance with EU legislation. It can be concluded that the current situation is still far from satisfactory.     

Solubility behavior of amphiphilic block and random copolymers based on 2‐ethyl‐2‐oxazoline and 2‐nonyl‐2‐oxazoline in binary water–ethanol mixtures

The solution properties of random and block copolymers based on 2‐ethyl‐2‐oxazoline (EtOx) and 2‐nonyl‐2‐oxazoline (NonOx) were investigated in binary solvent mixtures ranging from pure water to pure ethanol. The solubility phase diagrams for the random and block copolymers revealed solubility (after heating), insolubility, dispersions, micellization as well as lower critical solution temperature (LCST) and upper critical solution temperature behavior. The random and block copolymers containing over 60 mol % pNonOx were found to be solubilized in ethanol upon heating, whereas the dissolution temperature of the block copolymers was found to be much higher than for the random copolymers due to the higher extent of crystallinity. Furthermore, the block copolymer containing 10 mol % pNonOx exhibited a LCST in aqueous solution at 68.7 °C, whereas the LCST for the random copolymer was found to be only 20.8 °C based on the formation of hydrophobic microdomains in the block copolymer. The random copolymer displayed a small increase in LCST up to a solvent mixture of 9 wt % EtOH, whereas further increase of ethanol led to a decrease in LCST, which is probably due to the “water‐breaking” effect causing an increased attraction between ethanol and the hydrophobic part of the copolymer. In addition, the EtOx‐NonOx block copolymers revealed the formation of micelles and dynamic light scattering demonstrated that the micellar size is increasing with increasing the ethanol content due to the enhanced solubility of EtOx. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 515–522, 2009     

Synthesis of poly(methyl methacrylate)-<Emphasis Type="Italic">block</Emphasis>-poly(tetrahydrofuran) by photo-living radical polymerization using a 2,2,6,6-tetramethylpiperidine-1-oxyl macromediator

The synthesis of a poly(methyl methacrylate)-block-poly(tetrahydrofuran) (PMMA-b-PTHF) diblock copolymer was attained by the photo-living radical polymerization of methyl methacrylate using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) supported on the chain end of poly(tetrahydrofuran) (PTHF) as the macromediator. The polymerization was performed at room temperature by 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) as an initiator in the presence of bis(alkylphenyl)iodonium hexafluorophosphate as a photo-acid generator to produce the diblock copolymer consisting of poly(methyl methacrylate) (PMMA) and PTHF blocks connected through the TEMPO. The polymerization was confirmed to proceed in accordance with a living mechanism based on linear correlations for three different plots of the first order time-conversion, the molecular weight of the copolymer versus the monomer conversion, and the molecular weight versus the reciprocal of the initial concentration of the initiator. The molecular weight distribution of the block copolymer was dependent on the molecular weight of the macromediator based on the miscibility of PMMA and PTHF.     

A study of mercury(II)-catalysed substitution of cyanide in hexacyanoferrate(II) by 2-methylpyrazine: effects of inhibitor on the catalysed reaction

The kinetics and mechanism of the mercury(II)-catalysed ligand substitution reaction between potassium hexacyanoferrate(II) and 2-methylpyrazine (2-Mepz), in potassium hydrogen phthalate buffer of pH 3.50 ± 0.02 at 25.0 ± 0.1 °C and constant ionic strength of 0.1 M, were studied spectrophotometrically by measuring the absorbance of the yellow-coloured product at 447 nm (λ_max). The reaction was studied under pseudo-first-order conditions using excess of 2-Mepz. The reaction was found to obey first-order dependence in concentration of both [Fe(CN)₆]⁴⁻ and 2-Mepz. At higher concentrations of 2-Mepz, the effect of [2-Mepz] levels off. A complex behaviour is observed on varying [Hg²⁺]. The effect of pH on the reaction rate was also analysed. The effects of dielectric constant and water content of the reaction medium have been interpreted in terms of the formation of a polar activated complex and suggest an I_d mechanism. The inhibitory effect of 2,3-dimercaptopropanol on the reaction was also studied and explained in terms of binding of this species to the catalyst.     

Synthesis,characterisation and crystal structure of a cobalt(II)-hexamethylenetetramine coordination polymer

A novel one-dimensional zigzag coordination polymer, dinitrodiaqua-bis(hexamethylenetetramine)cobalt(II) was synthesised and characterised, and the structure was determined by single-crystal X-ray diffraction. The compound has a chain structure with each cobalt atom covalently bonded to two nitrate ions, two water molecules and two HMTA molecules, giving a slightly distorted octahedral geometry about the cobalt atom. Each HMTA ligand uses two of its N atoms to bond to two cobalt atoms giving an approximately bent Co–HMTA–Co configuration. Each chain is hydrogen bonded through OH···N and OH···O interactions with neighbouring chains leading to an overall polymer structure. Thermal studies show significant mass loss corresponding to the loss of the coordinated water molecules and the decomposition of both the nitrate ions and the HMTA.     

Synthesis and isolation of methyl bismuth cysteine and its definitive identification by high resolution mass spectrometry

After the synthesis and isolation of methylated bismuth cysteine, its initial identification by IR-spectroscopy was performed, whereas for definitive identification, high resolution mass spectrometry (ESI-TOF-MS and LTQ Orbitrap) was carried out.