Using Webcam, CdTe Quantum Dots and Flow-Batch System for Automatic Spectrofluorimetric Determination of N-Acetyl-L-cysteine in Pharmaceutical Formulations

The combination of a flow-batch system, quantum dots (QDs) and webcam as detector for the automatic spectrofluorimetric determination of N-acetyl-L-cysteine (NAC) in pharmaceutical formulations is proposed. NAC generates surface interactions that result in enhanced QD fluorescence intensity, which is proportional to analyte concentration. Wavelength selectors are not necessary for excitation and emission process due to the broad excitation spectrum of QDs, the selective and specific reaction between CdTe QDs and NAC, and the mathematical model employed for the treatment of digital images. The limit of detection and relative standard deviation were estimated at 0.14 mu g mL(-1) and < 1.4% (n = 5), respectively. The accuracy was assessed through recovery test (98.5 to 102.8%). The ruggedness of the method was assessed by comparison of the intra-and inter-day using the iodometric titration method at a 95% confidence level. The system presented satisfactory robustness, high sampling rate (153 h(-1)), and reduced chemical consumption.