Turn-on fluorescence probe for selective and sensitive detection of D-penicillamine by CdS quantum dots in aqueous media: Application to pharmaceutical formulation

Herein, we report on the development of a novel turn-on fluorescence probe for sensing of D-penicillamine (D-PA) using 3-mercaptopropionic acid (MPA) capped nanocrystalline cadmium sulphide quantum dots (MPA-CdS QDs) in aqueous solution. The fluorescence intensity of the MPA-CdS QDs was significantly enhanced in the presence of D-PA due to passivation of surface trap states of MPA-CdS QDs through the binding of mercapto group with Cd in core shell which results in the formation of new radiative electron-hole recombination centers. This is proved by some analytical techniques such as fluorescence, DLS and zeta potential measurement. Under the optimum conditions, the MPA-CdS QDs fluorescence probe offers good sensitivity and selectivity for detecting D-PA. The probe offers good linear relationship between 0.1 and 0.8 mu g mL(-1) for D-PA with limit of detection (LOD) and limit of quantification (LOQ) are 0.1123 mu g mL(-1) and 0.3402 mu g mL(-1), respectively. The method was successfully employed for the analysis of D-PA content in commercial pharmaceutical formulation and revealed quantities almost equal to those measured using the standard method, and demonstrated good accuracy and precision. The common excipients used as additives in pharmaceuticals did not interfere in the proposed method. The method is rapid, simple, accurate and precise without the need for authentic analyte standards. It could therefore be used as an alternative to the quantification of D-PA in pharmaceutical formulations. (C) 2014 Elsevier B.V. All rights reserved.