Discrimination of penicillamine enantiomers using β-cyclodextrin modified CdSe/ZnS quantum dots

The authors describe a method for the differentiation of penicillamine (PA) enantiomers by using CdSe/ZnS quantum dots (QDs) modified with β-cylodextrin (β-CD-CdSe/ZnS QDs). Selective enantiorecognition of L-PA and D-PA was accomplished by virtue of selective host-guest interaction between the PAs and the β-CD pockets on the QDs. The fluorescence intensity of the modified QDs decreases in the presence of L-PA. On the contrary, it increases in the presence of D-PA. These findings form the basis for a new method for recognition of PA enantiomers. Under optimized conditions, a linear relationship exists between fluorescence intensity and D-PA concentration in the 0.1 to 5.0 mg L−1 range, and between 0.8 and 5.0 mg L−1 for L-PA. Detection limits are 0.06 mg L−1 for D-PA, and 0.2 mg L−1 for L-PA. The potential of this method has been demonstrated by the determination of D-PA in pharmaceutical formulations and L-PA in (spiked) environmental samples.