A new liquid chromatography–fluorescence method for determination of perfluorooctanesulphonyl fluoride upon derivatisation with 1-naphthol

Perfluorooctanesulphonyl fluoride (PFOSF), as a main precursor of perfluorooctanesulphonate (PFOS) that is ubiquitous in the environment, has been released to the environment with substantial quantity. Determination of PFOSF presents significant analytical challenges for using liquid chromatography with UV (LC–UV) and fluorescence detection (LC–FLD) due to the lack of chromophore in the molecular structure. In this study, a new method was developed by derivatising PFOSF with 1-naphthol to form 1-naphthylperfluorooctanesulphonate (NPFOS), which allowed rapid qualitative and quantitative analysis using LC–UV and LC–FLD. The derivatising product was confirmed from the analyses by proton nuclear magnetic resonance and quadrupole–time of flight mass spectrometry. The LC–FLD method demonstrated good linearity in the NPFOS concentration range from 20 pg µL^?1 to 20 ng µL^?1 with a correlation coefficient better than 0.999, with the instrument detection limit of 1.5 pg µL^?1.     

Effects of electrolytes on adsorbed polymer layers: poly(ethylene oxide)-silica system

The effects of various electrolytes on the adsorption of poly(ethylene oxide) onto silica have been studied. The salts were the chlorides of Na+, Mg2+, Ca2+, and La3+. The methods used were adsorption isotherms, found using a depletion method with phosphomolibdic acid, photon correlation spectroscopy, and solvent relaxation NMR. All the salts increased the particle-polymer affinity and adsorbed amount according to the adsorption isotherms, and a linear relationship was found between the initial slope of the isotherms and the ionic strength of the solution. Final adsorbed amounts were approximately 0.4-0.5 mg m(-2). The polymer layer thicknesses as found by PCS were of the same order as the radius of gyration of the polymer and increased with both the concentration and the valency of the salt due to increased adsorption. Solvent relaxation NMR showed that NaCl is too weak to have a noticeable effect on the polymer train layer, but the divalent salts clearly did increase both the strength of solvent binding close to the silica surface and the amount of PEO required to reach the maximum train density.     

Water-Mediated Epoxy/Surface Adhesion: Understanding the Interphase Region

Epoxy resins coatings are commonly found in corrosion protection coatings but the presence of water can affect their adhesion to the substrate, often weakening the adhesion of the coating to the solid, reducing its efficiency. Nevertheless, small amounts of water can enhance the epoxy/substrate interactions. In this work, the interphase region of an epoxy precursor and metal oxide substrates is investigated using molecular simulations and it is found that water accumulates between the epoxy layer and the solid substrate. At high water concentrations (9 wt %) the interaction between the epoxy precursor and the solid surface is weakened regardless of the nature of the solid, but at low water concentrations the nature of the solid surface becomes important. For hematite, the presence of water decreases the strength of adhesion but for goethite the presence of a small amount of water (3 wt %) enhances the adhesion to the surface resulting in a densification at the interface.     

Parameter studies of modal vibrations associated with impurity pinned dislocations in a metal single crystal

Koehler's model [1–2] of motion for edge‐type dislocations in a metal single crystal that are pinned down by impurity atoms is studied. An exact solution can be found, which is composed of a rapidly decaying transient and a steady time‐oscillating, steady state vibration. This solution is used to improve Koehler's [1] approximation to the steady time‐oscillating steady state vibration. General parameter studies of the modes of oscillation are then performed. The present result is of some significance, because it allows insight into the behavior of crystalline solids over a wide parameter range, whereas Koehler's asymptotic approach is valid only for materials that exhibit order‐of‐magnitude variation in system parameters. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17: 427–439, 2001.     

Physical contributions to the heat capacity of nickel

Heat capacity data for solid nickel have been re-evaluated and analyzed into physical contributions, 0–1726 K. Two new sets of measurements of C_p(Ni), 333–1500 K, have been combined with literature data to produce an evaluated data set with uncertainty ? ± 2%. These smoothed data have been analyzed into vibrational harmonic, electronic, magnetic and dilatational contributions with the aid of auxiliary measurements of expansion coefficient, compressibility, vibrational and electronic densities of states, elastic constants, and magnetic exchange integral and susceptibility obtained from the literature. The vibrational harmonic term is interpreted in terms of a θ_D-vs-T curve in accord with predictions of the density-of-states distribution. The electronic contribution is smaller than predicted by free-electron theory due to a large electron-phonon effect. The electronic term for paramagnetic nickel is in good agreement with that predicted from band calculations. The magnetic contribution yields a magnetic entropy in accord with theoretical predictions, and a magnetic internal energy and critical-point behavior in agreement with the isotropic Heisenberg model. The experimental heat capacity can be accounted for without reference to vibrational anharmonic and vacancy contributions, in accord with recent calculations.     

A small-angle neutron scattering study of adsorbed polymer structure in concentrated colloidal dispersions

Poly(ethylene oxide) (PEO) adsorption on colloidal silica particles was studied by small-angle neutron scattering under the core-contrast-matching condition. The volume fraction profile of the adsorbed layer was derived by modeling the average layer scattering term. It was found that, with increasing colloid concentration, the adsorbed PEO layers collapse due to the repulsions between adsorbed layers on neighboring particles. At the same time, the correlation length in the adsorbed layer obtained by fitting the layer fluctuation scattering term was found to decrease, indicating that denser polymer layers are formed. These two observations are self-consistent.     

Effect of age and food intake on dietary carbon turnover recorded in sheep wool

We present the results of a series of controlled feeding experiments with sheep, designed to investigate the effects of age and level of food intake on the kinetics of incorporation of the dietary carbon signal into wool. Four different groups of three sheep each, ranging in age from 6 to 78 months, were fed a C(3) diet and switched to a C(4) diet for up to 250 days. Different quantities of the same C(4) diet were provided to each group, in order to achieve different growth rates (high, low, and no growth). Wool was repeatedly shorn from each animal and processed for delta(13)C analyses. Results show that newly grown wool does not start recording the isotope composition of the new diet immediately after the diet-switch. The time-lag varies according to the age of the animal, from 6 +/- 1 days in lambs to up to 15 +/- 4 days in the older ewes. Wool from fast-growing lambs approached equilibrium faster than that from slow-growing lambs and young ewes, with old ewes being the slowest. However, 3 weeks after the diet-switch, the differences in wool delta(13)C values between the four different groups of animals were relatively small and represented less than 15% of the isotopic difference between the two diets. These results suggest that a single equation can be used to reconstruct previous diets for animals of different age, provided that the diet is similar and all individuals are in positive protein balance.     

Use of a tandem Prins/Friedel-Crafts reaction in the construction of the indeno-tetrahydropyridine core of the haouamine alkaloids: formal synthesis of (-)-haouamine A

A tandem Prins/Friedel-Crafts reaction useful for the construction of the indeno-tetrahydropyridine core of the haouamine alkaloids and a formal synthesis of (-)-haouamine A are described.     

The Crystal Structure of Orthocetamol Solved by 3D Electron Diffraction

Orthocetamol is a regioisomer of the well‐known pain medication paracetamol and a promising analgesic and an anti‐arthritic medicament itself. However, orthocetamol cannot be grown as single crystals suitable for X‐ray diffraction, so its crystal structure has remained a mystery for more than a century. Here, we report the ab‐initio structure determination of orthocetamol obtained by 3D electron diffraction, combining a low‐dose acquisition method and a dedicated single‐electron detector for recording the diffracted intensities. The structure is monoclinic, with a pseudo‐tetragonal cell that favors multiple twinning on a scale of a few tens of nanometers. The successful application of 3D electron diffraction to orthocetamol introduces a new gold standard of total structure solution in all cases where X‐ray diffraction and electron‐microscope imaging methods fail.