Chromatography Modeling Software Applicability for Non-Conventional Columns: a Case Study of Calixarene- and Resorcinarene-Bonded Stationary Phases

In this study a systematic evaluation of the applicability of DryLab for calixarene- and resorcinarene-bonded stationary phases and some other relatively new reversed-phase columns with the presence of conventional alkyl-bonded phases was carried out. Calixarene- and resorcinarene-bonded stationary phases belong to the reversed-phase materials. However, depending on the analytes, they show some additional interactions, since their steric, polar and ionic properties are different compared to those of conventional alkyl-bonded phases. Three different mixtures of model analytes, consisting of alkyl substituted benzene derivatives, 4-hydroxybenzoic acid esters and polycyclic aromatic hydrocarbons, were used to verify the accuracy of DryLab prediction of retention times and to compare the results of 20 different liquid chromatographic phases. The type and the content of the organic modifier as well as the temperature and the gradient time were systematically changed using same conditions for all stationary phases. The results showed that the prediction on the calixarene- and resorcinarene-bonded stationary phases as well as on other reversed-phase columns is highly accurate in both isocratic and gradient modes. The predictions and real experiments were highly correlated with an average absolute error (∆t _R) of 0.027 min (<2 s) and an average percent absolute error (%∆t _R) of 0.38 on the calixarene- and resorcinarene-bonded stationary phases, and ∆t _R of 0.04 min (<3 s); %∆t _R of 0.51 on the other reversed-phase columns in this study. As a result, DryLab could be applied with very accurate predictions in method development using calixarene- and resorcinarene-bonded stationary phases, which were used as an example for “new” stationary phase materials.

     

Uniform persistence for population interaction models with time delay

In this paper uniform persistence is establised for kolmogorov type Prey‐Predator and competion models with per capitals ent growth rates that are dependent on time‐lagged population densities.     

Single‐pulse pulsed laser polymerization–electron paramagnetic resonance investigations into the termination kinetics of n‐butyl acrylate macromonomers

The termination of model mid‐chain radicals (MCRs), which mimic radicals that occur in acrylate polymerization over a broad range of reaction conditions, has been studied by single‐pulse pulsed laser polymerization (SP‐PLP) in conjunction with electron paramagnetic resonance spectroscopy. The model radicals were generated by initiator‐fragment addition to acrylic macromonomers that were preformed prior to the kinetic experiments, thus enabling separation of termination from the propagation reaction, for these model radicals propagate sparingly, if at all, on the timescale of SP‐PLP experiments. Termination rate coefficients of the MCRs were determined in the temperature range of 0–60°C in acetonitrile and butyl propionate solution as well as in bulk macromonomer over the range of 0–100 °C. Termination rate coefficients slightly below those of the corresponding secondary radicals were deduced, demonstrating the relatively high termination activity of this species, even when undergoing MCR–MCR termination. For chain length of 10, a reduction by a factor of 6 is observed. Unusually high activation energies were found for the termination rate coefficient in these systems, with 35 kJ mol^?1 being determined for bulk macromonomer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012