Chiral separation of nanomole amounts of alprenolol with cITP/NMR

Jayawickrama, Dimuthu A.; Sweedler, Jonathan V.
March 2004
Analytical & Bioanalytical Chemistry;Mar2004, Vol. 378 Issue 6, p1528
Academic Journal
On-line cITP–NMR with chiral selectors separates and concentrates analytes and identifies host–guest interactions of analytes with selectivity enhancers in the electrolyte. An NMR microcoil designed for a 200 μm i.d. capillary creates a high-mass-sensitivity 30 nL NMR cell and is used as an on-line detector for cITP. Using a mixture of 2 nmol racemic alprenolol in acetate buffer with α-cyclodextrin and sulfated β-cyclodextrin at pD 6.0, cITP–NMR successfully separates and concentrates both R- and S-alprenolol. The concentration enhancement for the R isomer is 224-fold and for the S isomer is 200-fold. The estimated concentration at peak maximum for R-alprenolol is ~28 mmol L-1 and a slightly lower concentration, 25 mmol L-1 is achieved for S-alprenolol. These concentrations convert to placing 76% of the injected S-alprenolol and 84% of the R-alprenolol into the 30 nL detection cell at peak maximum. With on-flow cITP–NMR, intermolecular interactions between the cyclodextrins and the alprenolol are observed in the NMR spectra. Aromatic and methyl moieties of R- and S-alprenolol are identified as two important sites that bind with these particular cyclodextrins.


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