CONICET | Buscador de Institutos y Recursos Humanos

l-ascorbic acid (AA) is important in processes of oxidation and reduction in humans, participating in several metabolic reactions. AA has been used for the prevention and treatment of the common cold, mental diseases, infertility, cancer, and AIDS. Therefore, it is relevant to develop a sensitive and simple analysis tool for the determination of AA content in pharmaceutical samples. The purpose of this work was the quantitative determination of AA in pharmaceutical formulations using a lab-on-paper device coupled to fluorescence detection.The AA determination was carried out through LIF (laser-induced fluorescence) detection using a SVM340TM synchronized video microscope (LabSmith). For AA determination, HRP was immobilized on AP-SNs (3-aminopropyl functionalized silica nanoparticles) covalently attached on paper surface which was located on the microscope platform. To carry out the process of modification, 1 mg of AP-AP-SNs was allowed to react with 1 ml of an aqueous solution of 5% w/w glutaraldehyde at pH 10.00 (0.20 M carbonate) on paper surface for 1 h at room temperature. After three washes with 0.10 M phosphate buffer of pH 7.00, a 10 μg mL−1 of HRP enzyme solution was coupled to the residual aldehyde groups 1 h at 5 °C. HRP in the presence of H2O2 catalyses the oxidation of 10 acetyl-3,7 dyhidroxyphenoxazine to highly fluorescent resorfurin, which was measured by LIF detector, using excitation lambda at 550 nm and emission at 585 nm. Thus, when AA is added to the solution acts as mediator of HRP, decreasing the relative fluorescence signal proportionally to the increase of AA concentration. This method could be used to determine AA concentration in the range 11 nM ? 3 µM. The determination of AA acid was possible with a limit of detection of 5 nM. Based on the results, the proposed approach was successfully used to analyze the AA content in pharmaceuticals formulations.