Rayleigh instability of stationary phase films in capillary column chromatography

Abstract

SummaryThe film of stationary phase on the wall of a capillary column and that of the phase solution during both static and dynamic coating is subject to Rayleigh instability, which is quite independent of so-called wettability. A theory is developed which shows that the logarithmic growth rate of Rayleigh instabilities is proportional to thesurface tension and to the third power of the film thickness, and inversely to the viscosity and to the fourth power of the capillary diameter. Determination of the variation of the viscosities of stationary phase solutions with concentration in coating solvents, and the variation of the viscosities of neat stationary phases with temperature, both revealed that heating and/or diluting changed the viscosities of phases with n-electron-containing groups much more than for polydimethylsiloxanes. Rayleigh instability is therefore more important during coating of phenyl-containing phases such as OV-17, and later during column operation. The efficiencies of capillary columns of different diameters coated with a number of phases under different conditions of temperature and coating rate, and then operated at different temperatures were in good agreement with the predictions of the theory.

Preparation and evaluation of polyacrylate-coated fused-silica capillaries for reversed-phase open-tubular liquid chromatography

“…7 an illustration of the different film shapes can be found. The formation of a "pearl chain" film is attributed to the Rayleigh instability [12] and occurs when the viscosity of the polymer (related to the extent of cross-linking) is relatively small, as is the case when the irradiation time is short.…”

Narrow (5‐50‐μm i.d.) open tubular columns in liquid chromatography using immobilized polymethyloctadecylsiloxane as stationary phase

“…The time needed for evaporation of the solvent depends on the length and the internal diameter of the capillary as well as the properties of the stationary phase and the solvent. The evaporation time in this study varied between 1 and 7 h. The long coating time enhances the risk of Rayleigh instability [31]. This may result in a nonuniform stationary phase film and a lower column efficiency.…”

Unified multidimensional microcolumn chromatography

“…The use of open-tubular columns in GC and SFC is wellestablished (5,6), and research into the use of open-tubular columns in LC is currently being canied out (7). With the development during the past decade of fused-silica columns has come a better understanding of the chemistry of the column iMer wall and its deactivation (6), the physical chemistry of the coating process (7, 8), the availability of highly thermostable cross-linked stationary phases, and the concept of "designer" stationary phases with functional groups tailored for specific separations.…”