Pontos de carbono de Spondias Dulcis Parkinson aplicados à determinação fluorimétrica de ácido ascórbico em medicamentos

Abstract

This work presents a new fluorimetric method for determination of ascorbic acid in medicaments using carbon points (PCs) and a portable miniaturized spectrometer. The PCs were synthesized by hydrothermal carbonization in a single phase, using Spondias dulcis Parkinson as a bioprecursor and ethanolamine for doping with nitrogen (NPCs). The nanoparticles showed high cyan blue fluorescence (Max..emis. = 488 nm) when exposed to ultraviolet radiation (Max.exc. = 380 nm), with a quantum yield of 12.0%. Due to the internal filter effect, strong suppression of the fluorescence of the NPCs by chromium(VI) ions, recovered in the presence of ascorbic acid, due to the reduction to chromium(III) ion, was evidenced. The quantitative measurements were performed with 40 μL of the working solution of NPCs and concentration of 10 mg L-1 of chromium (VI) ion solution at pH 6.9 (phosphate buffer solution). With a linear range between 0.50 and 80,0 mg L-1 of ascorbic acid (R² = 0.998), the detection and quantification limits of 0.15 and 0.46 mg L-1, respectively, were calculated. The results of the analysis of variance, for a confidence level of 95%, showed that there is no lack of fit of the linear model and the regression is significant. An ascorbic acid recovery between 90.6 and 107 % was obtained, acceptable for drug analysis. The average of the ascorbic acid contents of the four solid samples was close to the nominal values labeled (500 mg and 1,000 mg), differently from the five liquid samples, since all the calculated results were below the nominal value of 200 mg mL-1, both for (161.0 mg mL-1 to 170.5 mg mL-1), evidencing probable degradation of the analyte in this presentation form of medicines.