Determination of the porosities of monolithic columns by inverse size-exclusion chromatography.

Retention data of polystyrene samples of narrow molecular size distribution and known average molecular mass were measured on several monolithic columns (Chromolith Performance, Merck) and one conventional packed column (Luna C18, Phenomenex) by size-exclusion chromatography. These data were used to determine the external, the internal, and the total porosities of these columns. These data provided also information on the pore-size distribution of the adsorbent medium.

Adsorption equilibria of butyl- and amylbenzene on monolithic silica-based columns.

The adsorption isotherms of butyl- and amylbenzene on silica monolithic columns were measured by frontal analysis. The external, internal and total porosities of these columns were determined by inverse size-exclusion chromatography. The adsorption isotherms are concave upward in the entire concentration range investigated.

Behavior of packing materials in axially compressed chromatographic columns.

The behavior of a packing material (Luna C18 from Phenomenex, Torrance, CA, USA) was studied during the consolidation of a column bed under axial compression stress. The kinetics of this consolidation, the permeability and efficiency of the columns obtained, and the reproducibility of these column properties were measured under different conditions. The consolidation process and the column properties are considerably affected by the friction between the packing material in the bed and the column wall.

Evaluation of the contribution of smoking to total blood polonium-210 in Saudi population.

A preliminary study of 210Po concentrations in the blood of some smokers and nonsmokers is presented in order to evaluate the contribution of smoking to total blood 210Po in Saudi population. Blood samples were collected from 30 volunteers and analyzed by high resolution alpha-spectrometry using a radiochemical technique. The technique is based on the separation of polonium from other components of the sample by wet ashing with an HNO3/H2O2 oxidizing mixture and spontaneous deposition on a silver disc under the relevant conditions for alpha-particle counting.