Cyclodextrins industrial applications

Cyclodextrins have a large range of industrial applications. The market for them is growing as a consequence of their unique inclusion properties and decomplexation kinetics in conjunction with their stability, non-toxicity and relative cheapness. Cyclodextrins are the main active ingredient in Procter and Gamble s deodorising product Febreze, for example, where their complexation ability binds molecules responsible for household odours. The principal areas of interest are summarised in Figure 6.26. Some 1,649 research papers were published with the word cyclodextrin in the title in 2006 alone. 

In addition to their use in pharmaceutical formulations, cyclodextrins have also been investigated for use in various industrial applications. Analytically, cyclodextrin polymers are used in chromatographic separations, particularly of chiral materials. 

In the chemistry of inclusion compounds, there is no doubt that cyclodextrins (CDs) belong to the most important class of host molecules. The remarkable career of cyclodextrins in research and industrial applications is due to their ability to incorporate selectively many organic/inorganic molecules, ions and even radicals. CDs have found numerous applications in many areas, especially in the pharmaceutical, agrochemical, food and tobacco industries, as well as in cosmetics and toiletry [8]. 

Hashimoto, H (2002). Present status of industrial application of cyclodextrins in Japan. Journal of Inclusion Phenomena and Macrocyclic Chemistry, 44,57-62. 

Hedges, AR (1998). Industrial applications of cyclodextrins. Chemical Review, 98,... 

The preferential affinity to EtOH depends on the balance between the hydro-philicity and the hydrophobicity of the membrane s material (Huang 1991). Qiu and Peinemann (2006) developed novel organic nanocomposite membrane for PV. The basic polymers were PDMS and poly(l-trimethylsilyl-l-propyne) (PTMSP). By implanting the hydrophobic organic molecules in PTMSP and PDMS, permselectivity to EtOH was enhanced. For example, PDMS with 20 wt% a-cyclodextrins provides a separation factor of 12 for EtOH (5 wt%)-water (95 wt%). Similarly, PTMSP with only 8 wt% a-cyclodextrins improved the enrichment of the low concentration of EtOH from 5 to 48 wt% and maintained the flux at 9 kg pm/m h. They claimed that the increased performance in EtOH-water separation with this organic nanocomposite membrane may lead to the practical industrial application by means of the PV process to produce bioethanol. 

Amann M, Dressnandt G. Cyclodextrms in cosmetics. Cosmet Toilet 1993 108 90-95. Szejtli J. Industrial applications of cyclodextrins. In Atwood JL, Davies JE, MacNicoI DD, eds. Inclusion Compounds. Vol 3 Physical Properties and Applications. London Academic Press, 1984 331-390. 

With capillary electrophoresis (CE), another modern primarily analytically oriented separation methodology has recently found its way into routine and research laboratories of the pharmaceutical industries. As the most beneficial characteristics over HPLC separations the extremely high efficiency leading to enhanced peak capacities and often better detectability of minor impurities, complementary selectivity profiles to HPLC due to a different separation mechanism as well as the capability to perform separations faster than by HPLC are frequently encountered as the most prominent advantages. On the negative side, there have to be mentioned detection sensitivity limitations due to the short path length of on-capillary UV detection, less robust methods, and occasionally problems with run-to-run repeatability. Nevertheless, CE assays have now been adopted by industrial labs as well and this holds in particular for enantiomer separations of chiral pharmaceuticals. While native cyclodextrins and their derivatives, respectively, are commonly employed as chiral additives to the BGEs to create mobility differences for the distinct enantiomers in the electric field, it could be demonstrated that cinchona alkaloids [128-130] and in particular their derivatives are applicable selectors for CE enantiomer separation of chiral acids [19,66,119,131-136]. 

Let us compare the methods applied by Pedersen for establishing the complex formation with a modern approach. Today tedious solubility studies are carried out almost exclusively with practical applications in mind, but they are not performed to prove the complex formation. For instance, one ofthe main reasons for the use of cyclodextrin complexes in the pharmaceutical industry is their solubilizing effect on drugs [8]. There, and almost only there, solubility studies are a must. As concerns spectroscopic methods, at present the NMR technique is one ofthe main tools enabling one to prove the formation of inclusion complex, carry out structural studies (for instance, making use of the NOE effect [9a]), determine the complex stability [9b, c] and mobility of its constituent parts [9d]. However, at the time when Pedersen performed his work, the NMR method was in the early stage of development, and thus inaccurate, and its results proved inconclusive. UV spectra retained their significance in supramolecular chemistry, whilst at present the IR method is used to prove the complex formation only in very special cases. 

Reviews, 1998, 98, (5) covers several aspects of CDs chemistry while the books listed below mainly present their applications (b) Comprehensive Supramolecular Chemistry, v. 3, J. Szejtli, Ed., Kluwer Academic Publishers, Elsevier, Oxford, 1996 J. Szejtli, Cyclodextrin Technology, Kluwer, Dordrecht, 1988 (c) Cyclodextrins and Their Industrial Uses, D. Duchene, Ed., Edition du Sante, Paris, France, 1987 New Trends in Cyclodextrins and Derivatives, D. Duchene, Ed., Edition du Sante, Paris, France. 1991 (d) W. Saenger, Angew. Chem. Int. Ed. Engl., 1980, 19, 344 W. Saenger, in Inclusion Compounds, J. T. Atwood. J. E. D. Davies, D. D. MacNicol, Eds., v. 2, Academic Press. London, 1984, p. 231 K. Harata, ibid., v. 5, 1991, p. 311. 

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