Buffer composition changes in background electrolyte during electrophoretic run in capillary zone electrophoresis

The electrophoretic behaviors of different analytes in capillary zone electrophoresis were studied by the Whole Column Imaging Detection (WCID). For capillary zone electrophoresis (CZE) in conventional buffer systems, non-constant sample plug movement characterized by progressive decrease of peak migration velocity was observed. The appropriate velocity decrease was correlated with a degree of ionization of the analyzed ion, thus the effect observed could be explained by fast buffer composition change resulting in the development of a non-linear pH gradient. To visualize the appropriate pH gradient, the concentration profile of initially uniformly distributed amphoteric substances was also monitored. The evolution of the concentration profile exhibited very complex dynamics. In addition, it was found that the nature of the electrode solutions strongly affect changes in the background electrolyte. In the case of traditional background electrolytes with an acid-base pair for electrode solutions a non-uniform ampholyte concentration developed quickly, leading finally to a quasi-stationary profile similar to those typical of IEF. Possible approaches to suppress a negative impact of the background electrolyte composition changes during electrophoretic run on CE-separation are presented herein. In particular it was observed that zwitterionic buffers are able to withstand prolonged electrolysis much better compared to traditional buffers.     

Photophysical, spectroscopic, and computational studies of a series of Re(I) tricarbonyl complexes containing 2,6-dimethylphenylisocyanide and 5- and 6-derivatized phenanthroline ligands

The ligand 2,6-dimethylphenylisocyanide (CNx) forms six complexes of the formula [Re(CO)3(CNx)(L)]+, where L = 1,10-phenanthroline (1), 5-chloro-1,10-phenanthroline (2), 5-nitro-1,10-phenanthroline (3), 5-methyl-1,10-phenanthroline (4), 5,6-dimethyl-1,10-phenanthroline (5), and 1,10-phenanthrolinopyrrole (6). The lowest-energy absorption peaks of the complexes red-shift in the order 1 < 2 < 3 < 4 < 5 < 6. The time-dependent density functional theory (TDDFT) and conductor-like polarizable continuum model (CPCM) computed singlet excited states in ethanol deviate by 1000 cm(-1) or less from the experimental UV-vis peaks. The complexes undergo reversible reductions and irreversible oxidations. The electronic energy gap increases in the order 3 < 2 < 1 < 4 < 5 < 6, which is the order of increasing electron-donating power of the phen substituents. The reduction potentials linearly correlate with the B3LYP calculated LUMO energies for 1-6. The complexes emit at room temperature and at 77 K except 3, which emits only at 77 K. The calculated (3)MLLCT energies are within 1100 cm(-1) from the experimental emission energies at 77 K. The 77 K emission curve-fitting analysis results agree with the computational assignment of the emitting state as 3MLLCT for 1-5 and 3LC for 6. The experimental 77 K emission energies and the calculated 3MLLCT state energies increase in the order 6 < 5, 3 < 2 < 4, 1. The 77 K emission lifetimes increase upon addition of substituents from 65 micros for 1 to 171 micros for 2, to 230 micros for 4 and 5, and to 322 micros for 3. The emission quantum yields at room temperature in solution are 0.77, 0.78, 0.83, 0.56, and 0.11 for complexes 1, 2, 4, 5, and 6, respectively.     

A complete 1H and 13C NMR data assignment for 3-phenylmethylene-1H,3H-naphtho-[1,8-c,d]-pyran-1-one

Complete assignments of the 1H and 13C NMR chemical shifts for 3-phenylmethylene-1H,3H-naphtho-[1,8-c,d]-pyran-1-one were done by means of one- and two-dimensional NMR techniques, including 1H-(1)H COSY, HMQC and HMBC spectra. Ab initio quantum chemistry calculations and a shift prediction by an incremental method provided values close to the proposed assignments. All mid-IR spectral bands are given as reference data. The DRIFT FTIR, ATR FTIR and Raman spectra are given as a Supplementary data in JCAMP-DX format, version 4.24. In addition, a method of compound's synthesis, that has the product yield higher as compared to already known data in the literature, is given.     

Novel surface tension isotherm for surfactants based on local density functional theory

In this Letter we report a new general method for calculating of surface tension isotherms in the presence of surfactants, based on a local density functional. We illustrate this method by deriving the interfacial tension isotherm for nonionic surfactants at an air-water or oil-water interface by using the self-consistent field theory of polymer brushes. We consider a particular case of local density functional to calculate explicitly how the interfacial tension and the surfactant adsorption depend on the surfactant bulk concentration. Experimental data for the surface tension and the surfactant adsorption isotherm for nonionic surfactants were interpreted with the help of the new isotherm. Very good agreement between the adsorption of n-dodecyl pentaoxyethylene glycol ether (C12E5) at an air-water interface, calculated from the surface tension isotherm and small-angle neutron-scattering is obtained.     

Dipole excitations in 122Te, 126Te and 130Te

Excited states of the nuclei ¹²²Te, ¹²⁶Te and ¹³⁰Te were populated via the (γ, γ') reaction at endpoint energies of the bremsstrahlung between 4.5 and 5.5 MeV. Gamma rays were detected with a EUROBALL-CLUSTER detector and a single detector. In all nuclei several dipole transitions were identified at energies around 3 MeV. The lowest corresponding J = 1 states are interpreted as two-phonon excitations. Quasiparticle-phonon-model calculations predict one 1^? state arising from the coupling of the first quadrupole and the first octupole phonon and one 1⁺ state arising from the coupling of the first and the isovector second quadrupole phonon at about 3 MeV. The calculated transition strengths are compatible with experimental ones.     

A study of an elastomeric coating based on EPDM of cold vulcanization

Studies of the thermostability of vulcanizates of ethylene–propylene–diene rubbers (EPDM) obtained by using dinitrosogenerating systems of low-temperature vulcanization are performed. It is shown that vulcanizates retain sufficient high properties in operation up to 200°C for a long time. The use of such compositions for producing thin rubber coatings applied on a number of insulating materials allows the effect of energy saving to be obtained.     

The effect of aminoalkoxy and glycidoxyalkoxy silanes on adhesion characteristics of double and triple copolymers of ethylene

The effect of aminoalkoxy and glycidoxyalkoxy silanes on strength of a polyethylene-modified copolymer-metal (polyethylene terephthalate) adhesion joint was studied for double and triple acetate copolymers of ethylene. It was shown that such modification resulted in an essential increase in the deformation-strength and adhesion characteristics of adhesive joints.     

Adhesive properties of binary mixtures of some ethylene copolymers

It is shown using the example of polyolefin thermoplasts that the value of adhesion strength is determined by the mechanical properties of a composition.