Norman A. Parris

Non-aqueous reversed-phase liquid chromatography : A neglected approach to the analysis of low polarity samples

Abstract It has been found that mnay hydrophobic substances such as hydrocarbons and glyceride oils may not completely elute from a reversed-phase liquid chromatographic column when using semi-aqueous mobile phases containing methanol or acetonitrile. Addition of lower-polarity solvents such as methylene chloride or tetrahydrofuran to the carrier causes rapid elution of these non-polar susbtances. By using a highly retentive reserved-phase packing. Zorbax ODS, it has been demostrated that non-aqueous mobile phases provide an effective way of separating water-insoluble, non-polar substances. The enhanced solubility of compounds in these non-aqueous solvents greatly facilitates the detection of compounds which have poor UV absorbance/fluorescence characteristics.

Non-aqueous reversed-phase chromatography of glycerides using infrared detection

Summary Non-aqueous reversed-phase liquid chromatography has been found to provide an effective means of resolving complex mixtures of low-polarity substances present in glyceride-based oils. The most selective elution conditions from a column containing Zorbax ODS chromatographic packing are obtained with mobile phases formed from methylene chloride or tetrahydrofuran and acetonitrile. Separation of the essentially UV-transparent glyceride-type solutes can be monitored by either differential refractive index or infrared detection. The latter method has the advantage that temperature control of the detector is unneccessary and that the wavelength of operation imparts a degree of specificity to the detection system. By using infrared detection, it has been possible to monitor separations carried out under gradient elution conditions.

Preparative columns in high-speed liquid chromatography

Abstract When high-speed liquid chromatography is used to obtain pure material for subsequent investigation, it can correctly be called preparative, regardless of the sample weights employed. In this paper, the requirements for scaling up from a small-diameter analytical column to larger-diameter preparative columns are presented. An example of the use of high-speed preparative liquid chromatography to isolate and identify the components of a complex mixture is presented. General requirements of sample size for subsequent investigation are discussed.