Automatic Flow-Batch Approach Using CdTe Quantum Dots for Fluorescent Determination of Ascorbic Acid in Fruit Juices

This paper introduces, for the first time, the combination of the advantageous features of the automatic flow-batch system for implementing quantitative chemical analysis involving the use of quantum dots (QDs). For illustration, the combined QD-flow-batch system was applied for the fluorescent determination of ascorbic acid in fruit juices. Cadmium telluride (CdTe) QDs were selected in this work because they are the most commonly synthesized and used ones for the analytical applications. Water-soluble CdTe QDs were successfully produced using mercaptopropionic acid. The analytical method is based on the quenching effect produced by ascorbic acid on the fluorescence of CdTe. All calibration solutions were prepared in-line, and all analytical processes were completed by simply changing the operational parameters in the control software. The limit of detection and relative standard deviation were estimated at 3 μg L^?1 and ≤1.4 % (n = 5), respectively. The accuracy was assessed through recovery test (97.9 to 103.1 %). The ruggedness of the method was assessed by comparison of the intra- and interday using the official AOAC method at a confidence level of 95 %. The proposed system presented satisfactory robustness, high sampling rate (69 h^?1), and reduced chemicals consumption. Thus, the combination of flow-batch system and QDs is potentially useful as an alternative for other fluorimetric determinations.