Conclusion

Modern CCC is a novel form of preparative LLC that offers more versatility in the choice of solvents, ranging from very lipophilic to moderately polar organic or aqueous systems. It provides predictable retention behaviour and complete recovery of sample since retention depends only on the solute partition coefficient and adsorption is precluded by the inert nature of the apparatus. Its separation capability is further enhanced by various technical manipulations of solvent composition and flow during chromatogra-phy, which cannot be reproduced in other types of chromatography. CCC has been widely employed by

COOH COOH

COOH COOH

0 10 20 30 40 50 60 70 80 90 100 110 Fraction No. 0 20 40 60 80 100 120 140 160 180 200 220 Time (min)

Figure 6 Separation of 2- and 6-nitro-4-chloro-3-methoxybenzoic acids by pH-zone-refining CCC. Initial stationary phase is 0.3% (12 mM) trifluoroacetic acid in the upper organic phase of a mixture of methyl t-butyl ether/acetonitrile/water - 4:1 : 5 (v/v/v). The mobile phase was 0.8% (100 mM) ammonia in the lower aqueous phase pumped at 3mL min-1. The column volume is 310 mL. Reproduced from Dudding T, Mekonnen B, Ito Y and Ziffer H (1998) with permission from Marcel Dekker.

0 10 20 30 40 50 60 70 80 90 100 110 Fraction No. 0 20 40 60 80 100 120 140 160 180 200 220 Time (min)

Figure 6 Separation of 2- and 6-nitro-4-chloro-3-methoxybenzoic acids by pH-zone-refining CCC. Initial stationary phase is 0.3% (12 mM) trifluoroacetic acid in the upper organic phase of a mixture of methyl t-butyl ether/acetonitrile/water - 4:1 : 5 (v/v/v). The mobile phase was 0.8% (100 mM) ammonia in the lower aqueous phase pumped at 3mL min-1. The column volume is 310 mL. Reproduced from Dudding T, Mekonnen B, Ito Y and Ziffer H (1998) with permission from Marcel Dekker.

natural product chemists for the isolation and purification of unstable bioactive materials from complex matrices. The technique deserves more attention from analytical chemists confronted with the separation of complex mixtures, synthetic chemists facing purification of non-crystalline products, diastereomers or optical resolution of racemates, and physical chemists seeking new approaches to the study of solvent interactions or the measurement of chemical properties such as partition coefficients or dissociation constants. Continuing study of new applications of CCC in several laboratories, as well as the commercial development of more reliable and user-friendly apparatus, promises to extend the use of CCC in the foreseeable future.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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