FUNCTIONALIZED ALPHA-CYCLODEXTRINS AS POTENTIOMETRIC CHIRAL SENSORS

Octylated cyclodextrins have been synthesized and characterized by mass spectrometry (+ fast atom bombardment, + field desorption) and 500 MHz H-1 nuclear magnetic resonance spectroscopy. These highly lipophilic, enantiomerically pure molecules have been incorporated into solvent polymeric membranes and investigated as electrochemical sensors for chiral molecules incorporating aryl rings. Bis(1-butylpentyl) adipate (BBPA) and ortho-nitrophenyl octyl ether (o-NPOE) were used as plasticizers. Electrodes using BBPA as the plasticizer were stable and well defined with a limit of detection for ephedrine of -log[c] = 6.5. Interference from serum levels of Na+, K+ and Ca2+ is minimal; the best value obtained for -log k(pot) (the over-all selectivity coefficient) was 3.9 with BBPA as plasticizer and 1 X 10(-3) mol dm-3 NH4Cl as inner filling solution. The electrodes were highly enantioselective in binding ephedrine (enantioselectivity k(+)/(-)pot, 2.7). The o-NPOE-based electrodes, although enantioselective with minimal interference from serum levels of Na+, K+ and Ca2+, behaved in a time-dependent manner.