Nonaqueous reversed-phase liquid chromatography

HJCF Nelis, AP De Leenheer. Isocratic nonaqueous reversed-phase liquid chromatography of carotenoids. Anal Chem 55 270-275, 1983. 

Most HPLC is based on the use of so-called normal-phase columns (useful for class separations), reverse-phase columns (useful for homolog separations), and polar columns (used in either the normal- or reverse-phase mode). Since reverse-phase HPLC columns are generally easier to work with, almost all authors use high-performance reverse-phase liquid chromatography with octade-cyl chemically bonded silica as the stationary phase and nonaqueous solvents as mobile phases (so-called NARP, or nonaqueous reverse-phase chromatography). 

Fnhanced-fluidity liquid reversed-phase chromatography has numerous applications including the separation of nonpolar and polar compounds. For example, EFLC and nonaqueous reversed-phase HPLC are the common means of achieving effective separations of high molecular weight homologous compounds. 

A nonaqueous reversed-phase high-performance liquid chromatography (NARP-HPLC) with refractive index (RI) detection was described and used for palm olein and its fractions obtained at 12.5°C for 12-24 h by Swe et al. (101). The objective of their research was to find the optimum separation for analysis of palm olein triglycerides by NARP-HPLC, and to find a correction factor to be used in calculating CN and fatty acid composition (FAC). The NARP-HPLC method used to determine the triglyceride composition was modified from the method of Dong DiCesare (88). Palm olein was melted completely at 70°C in an oven for 30 min prior to crystal-... 

WO Landen Jr, RR Eitenmiller. Application of gel permeation chromatography and nonaqueous reverse phase chromatography to high pressure liquid chromatographic determination of retinyl palmitate and /3-carotene in oil and margarine. J Assoc Off Anal Chem 62 283-289, 1979. 

Abbott, T, Peterson, R., McAlpine, J., Tjarks, L., and Bagby, M. (1989) Comparing centrifugal countercurrent chromatography, nonaqueous reversed phase HPLC and Ag ion exchange HPLC for the separation and characterization of triterpene acetates. J. Liquid Chromatogr. 12, 2281-2301. 

Countercurrent chromatography is based on the distribution of substances in two liquid phases [128,129]. The liquid is fed into a coiled tube that is moved along an orbital trajectory. Due to centrifugal power, the liquids move in a counter-current. For proteins and many other biomolecules, this method is not practical because of denaturation in a nonaqueous phase. In aqueous two-phase systems, at least one phase exhibits high viscosity and, therefore, mass transfer between the two phases is limited. Similar problems occur with reversed micelle extraction as were observed with the aqueous two-phase extraction [130]. CCC has not been used for large-scale purification of proteins and other biopolymers. 

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