Computer simulation and enantioselective capillary electrophoresis to characterize isomer mixtures of sulfated β‐cyclodextrins

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EarlyView Article

  • Published: Nov 24, 2017
  • Author: Saara Mikkonen, Jitka Caslavska, Vlastimil Hruška, Wolfgang Thormann
  • Journal: ELECTROPHORESIS

Abstract

The enantiomeric separation of methadone in the presence of multiple isomer mixtures of sulfated β‐cyclodextrin (S‐β‐CD) was studied experimentally with CZE and theoretically using computer simulation. Experiments were performed over many years with several lots of S‐β‐CD from the same manufacturer with a specified degree of substitution of 7–11. Large differences in the migration patterns were observed between certain lots and it was concluded that the extent of labelling in lots released after a transition time was higher than originally specified. The migration pattern was observed to be associated with (i) the ionic strength increase resulting from using S‐β‐CDs with a higher charge state and (ii) differences in buffer composition. Apparent binding constants between methadone and the S‐β‐CD and complex mobilities were determined for different lots of S‐β‐CD at varying ionic strength using phosphate and 3‐morpholino‐2‐hydroxypropanesulfonic acid buffers. The obtained values were used as input for simulations. For a given ionic strength, agreement between predicted and experimentally observed behavior was obtained for different buffers. R‐methadone has a stronger interaction with S‐β‐CD than S‐methadone. For any given configuration there is a distinct S‐β‐CD concentration range which results in the cationic migration of S‐methadone while the migration direction of R‐methadone is reversed. This configuration was demonstrated to be applicable for micropreparative CZE separations.

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