Volume Of Stationary Phase Research Articles

Swollen polysiloxanes as stationary phases in reversed-phase open-tubular column liquid chromatography

A new liquid stationary phase was created after swelling cross-linked polysiloxanes with non-polar organic solvents in 11–55 μm I.D. fused-silica open-tubular columns. By choosing different polysiloxane/swelling solvent pairs, the stationary phase film thickness, retention and selectivity could be adjusted within a wide range. Using n-heptane as the swelling solvent, the film thickness increased by a factor of 3–4. Mobile to stationary phase volume ratios, β  V m/ V s, down to 2 were obtained. An increase in retention of 12–16 times after swelling was observed. Improved stability was obtained as compared with conventional liquid—liquid chromatographic systems with mechanically held stationary phases. The system was stable at very high flow-rates (up to 6.3 cm/s) and showed no mechanical loss of the stationary phase.

Chromatographic characterization of phenothiazine drugs by a reversed-phase thin-layer technique

A reversed-phase thin-layer chromatographic technique was used for the characterization of 26 phenothiazine drugs. With two chromatographic systems having the same stationary phase and phase volume ratio, but mobile phases of different pH, all but two of the compounds could be identified. R F values in the different systems were standardized by applying a reference compound to the paltes next to each compound under investigation; the corrected R F values were calculated from the differences in the R M values of the compounds and the reference compound, and the theoretical R M value of the reference. It was shown that R F values for different chromatographic systems with the same stationary phase could be predicted with reasonable accuracy. The pH of the mobile phase, for which a maximum difference in R F values was obtained for pairs of compounds, could also be calculated and corresponded well with the observed values.

A correlation between the specific surface area of GLC column packings and the stationary phase volume

A correlation between the specific surface area of the column packings for GLC and the volume of stationary phase has been derived on the basis of a parabolic approximation of pore volume distribution according to pore diameters. The validity of the correlation has been examined for six series of column packings, the obtained results being in good agreement with the experimental ones.

Evaluation of changes in the specific surface area of sorbents based on the volume of stationary phase in gas-liquid chromatography

Specific surface areas of sorbents were studied as a function of the coating volume of the stationary phase. Equations are suggested for the calculation of the distribution of pore volumes according to their diameters, based on the relative surface areas of chromatographic supports loaded with various volumes of the stationary phase. The results are compared with distribution curves obtained experimentally by porosimetric measurements.

Versatile System for Partition Chromatography of Corticosteroids and Prediction of Their Elution Curves

The versatile solvent system of n-hexane-chloroform-dioxane-water in the ratio 90:10:40:5 was used for the partition chromatographic isolation of corticosteroids. The relative amounts of the components may be adjusted if necessary to give a convenient partition coefficient on a diatomaceous earth column. Data are presented for 17 steroids, showing the close agreement between partition coefficients predicted from chromatographic elution curve data and those calculated from solvent extraction data. A procedure for the experimental determination of column parameters is given, and the necessary equations are outlined. The prediction of peak elution volumes and solute bandwidths as a function of partition coefficients from the derived equations is demonstrated, and the quantitative effect of varying the stationary phase volume and column length is calculated. The effect of steroid side-chain structure and fluoride substitution on the partition coefficient was studied. The effect of the substituents can be estimated from their expected polarity.

Etudes theoriques et pratiques sur la realisation et le fonctionnement de colonnes preparatives de diametre moyen. Modification de la structure interne de ces colonnes

The dependence of the efficiency and productivity of preparative-scale gas-chromatographic columns on various parameters is discussed. The minimum HETP is experimentally shown to increase almost proportionally to the column diameter in the range 1–5 cm. The HETP also increases with a power of the sample amount which depends on the quality of the column packing and can be as low as 1.2. High-diffusivity carrier gases (H 2 and He) arc shown to allow a three-fold increase of columns productivity. The productivity (amount of sample separated/unit time) increases with the column diameter. Given a fixed volume of stationary phase and a known mixture, the column diameter which will accept the largest sample can be calculated. The performance of a preparative unit is limited more by the loadability of columns than by loss of efficiency witli increasing diameters. The performances of preparative columns can be improved by putting rods parallel to the column axis regularly spaced in the packing. The column can be heated internally cither for programmed temperature separations or to allow thermal equilibrium to be reached rapidly.