title: Chemiluminometric determination of ascorbic acid in pharmaceutical formulations exploiting photo-activation of GSH-capped CdTe quantum dots.
abstract: An automated multi-pumping flow system is proposed for the chemiluminometric determination of ascorbic acid in pharmaceutical formulations, relying on the ability of semiconductor nanocrystals to generate short-lived reactive species upon photo-irradiation. A photo-unit based on visible-light-emitting diodes is used to photo-excite cadmium telluride (CdTe) quantum dots capped with glutathione, leading to the generation of radicals that react with luminol under alkaline conditions, yielding the chemiluminescence. Ascorbic acid acts as a radical scavenger, preventing the oxidation of luminol, thus ensuring a concentration-dependent chemiluminescence quenching. After system optimization, a linear working range of 5.0 × 10(-7) to 5.0 × 10(-6) mol/L ascorbic acid (r = 0.9967, n = 5) was attained, with a detection limit of 3.05 × 10(-7) mol/L and a sampling rate of 200/h. The flow system was applied to the analysis of pharmaceutical formulations and the results were in good agreement with those obtained by the reference titrimetric procedure (RD < ± 4.3%, n = 7).
authors.affiliation: NAPTISA/Center for Nuclear Energy in Agriculture, University of Sao Paulo, Piracicaba, Brazil.
authors.forename: M K
authors.initials: MK
authors.lastname: Sasaki
authors.forename: D S M
authors.initials: DS
authors.lastname: Ribeiro
authors.forename: C
authors.initials: C
authors.lastname: Frigerio
authors.forename: J A V
authors.initials: JA
authors.lastname: Prior
authors.forename: J L M
authors.initials: JL
authors.lastname: Santos
authors.forename: E A G
authors.initials: EA
authors.lastname: Zagatto
mesh_terms: D001205:Ascorbic Acid / Q000032:analysis*; D019187:Cadmium Compounds / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical; D005978:Glutathione / Q000737:chemistry*; D008163:Luminescent Measurements; D008165:Luminol / Q000737:chemistry; D015394:Molecular Structure; D055668:Photochemical Processes; D045663:Quantum Dots; D017382:Reactive Oxygen Species; D013691:Tellurium / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D017382:Reactive Oxygen Species; D008165:Luminol; D005978:Glutathione; D013691:Tellurium; D001205:Ascorbic Acid; C028337:cadmium telluride
keywords: ascorbic acid; chemiluminescence; multi-pumping flow system; pharmaceutical formulations; quantum dots