M. Kubín

Influence of the Amount of Bonded Non-Polar Phase and of the Length of Attached Alkyl Chains on Retention Characteristics of Silica-Based Sorbents for Reversed-Phase High Performance Liquid Chromatography

Abstract The retention characteristics of two sets of chemically bonded non-polar silica packings with a high surface concentration of functional groups have been compared in the reversed-phase mode of liquid chromatography: (i) the conventional packings prepared by chemical modification with trimethylsilyl, heptyl, dodecyl and octadecyl groups, and (ii) mixed-phase materials where differences in the amount of organic bonded phase were achieved by bonding octadecyl and trimethylsilyl groups in different proportions. The retention data of two homologous series of solutes show that these two classes of packings are distinctly different; in particular, the capacity factors and selectivities are always higher on the mixed-phase bonded silica packings at the same percentage of carbon.

Numerical evaluation of the size distribution of particles obtained by suspension polymerization using data of the Coulter Counter TA II apparatus

Abstract The particle size distribution determined by means of the Coulter Counter TA II (CC TA II) apparatus was compared with two artificial distributions prepared from fractions of polymeric spherical particles. The data were numerically treated using a new distribution function, and the fit was satisfactory. The applicability of CC TA II along with the numerical and graphic evaluation is documented for a real sample of the product of suspension radical polymerization.

Calibration of Size-Exclusion Chromatography Systems with Polydisperse Standards

Abstract Soon after its introduction to polymer science (1), size-exclusion chromatography (SEC) matured into an important tool for the determination of molecular weights and, in particular, molecular weight distributions (MWD) of diverse synthetic macromolecules, and superseded almost completely the older, tedious and less reliable fractionation methods. Different aspects of SEC have been covered in many monographs – the more recent are, e.g., (2 – 4) and reviews including articles that deal specifically with calibration and data evaluation procedures (5 – 8).

Efficiency of Glass CGC Columns in Reversed-Phase HPLC

Abstract The design of metal-jacketed glass columns of CGC type is described, and the dependence of their efficiency on the flow rate is given, both for a single column and for two columns combined in series. The results have been treated in terms of reduced quantities; the optimal values of the reduced plate height h∼2.5 suggest a good quality of the sorbent packing. It is shown that the described combination of columns in series does not reduce the total efficiency of the system.