High-temperature liquid chromatography. Part II: Determination of the viscosities of binary solvent mixtures--implications for liquid chromatographic separations.

This paper is the second in a series of consecutive publications, explaining the concept of high temperature liquid chromatography under various important aspects. The second publication deals with the determination of the viscosity of binary solvent mixtures used in reversed phase liquid chromatography in a temperature range between 25 and 250 degrees C. In literature, only limited data of the temperature dependent viscosities of liquid solvents or binary solvent mixtures can be found. Therefore, the viscosities of the pure solvents as well as the binary mixtures had to be determined experimentally up to 250 degrees C. The viscosity data were used to estimate the pressure drop in a capillary connecting a high-temperature HPLC system with a mass spectrometer. The solvent perturbation could be avoided by adjusting the diameter of the transfer capillary to the viscosity and vapour pressure of the mobile phase. The viscosity data were also used to show that a significant gain in analysis speed is theoretically feasible. This factor clearly depends on the nature of the solvent system, because for mixtures with a large viscosity maximum at ambient temperature, this effect is most pronounced.

High-temperature liquid chromatography. Part III: Determination of the static permittivities of pure solvents and binary solvent mixtures--implications for liquid chromatographic separations.

This paper is the third in a series of three publications, explaining the concept of high-temperature liquid chromatography under various important aspects. The third publication deals with the determination of the static permittivities of pure solvents and binary solvent mixtures used in reversed-phase liquid chromatography in a temperature range between 25 and 200 degrees C. Furthermore, a critical comparison is made between the polarity parameter which is generally used to define the elution strength of solvent mixtures and the experimentally determined static permittivities. Also, the necessity for using binary solvent mixtures at elevated temperatures is discussed for efficient method development.

High-temperature liquid chromatography. Part I. Determination of the vapour pressures of binary solvent mixtures--implications for liquid chromatographic separations.

This paper is the first in a series of consecutive publications, explaining the concept of high-temperature liquid chromatography under various important aspects. The first publication deals with the determination of the vapour pressure of binary solvent mixtures used in reversed-phase liquid chromatography. Also, the practical implications regarding the use of elevated temperatures in liquid chromatography and towards commercially available HPLC systems are explained.