Flow-based determination of methionine in pharmaceutical formulations exploiting TGA-capped CdTe quantum dots for enhancing the luminol-KIO4 chemiluminescence

A novel flow-injection chemiluminescence method (FI-CL) was established for the determination of methionine in this paper, based on its strong enhancement on CL intensity of the luminol-KIO4 system catalyzed by thioglycolic acid-capped CdTe quantum dots in alkaline media. Under the optimized conditions, the relative CL intensity was in proportion to methionine concentration in the range from 1.0 x 10(-8) to 1.0 x 10(-5) g mL(-1) with a detection limit of 6.6 x 10(-9) g mL(-1) (3 sigma). The relative standard deviation (RSD) of the CL intensity for 1.0 x 10(-6) g mL(-1) standard methionine solution was 0.97% (n=11). The proposed method was successfully applied to determine methionine in commercial pharmaceutical formulations with recoveries between 98.0% and 101.9%. The possible CL mechanism was discussed as well. (C) 2016 Elsevier B.V. All rights reserved.