Flow injection analysis of furosemide in pharmaceutical formulations using electrochemically reduced graphene oxide modified electrode

Graphene-based materials, such as reduced graphene oxide, have been widely used in electroanalysis due to their excellent electronic, thermal and mechanical properties[1]. The electrochemical reduction of graphene oxide (GO) was carried out on the surface of a glassy carbon electrode (GCE) using the cyclic voltammetry technique. Electrochemically reduced graphene oxide (ERGO) was characterized using Raman spectroscopy, SEM, XPS, AFM, and EIS technique. From the Raman spectra, the ID / IG ratio (disorder degree) was used and estimated as 0.98 and 1.15, respectively for GO and RGO, indicating that the electrochemical reduction promoted a structural disorganization that could be related to the reestablishment of the double carbon bonds present in the ERGO. The XPS data also confirm the reduction of GO to ERGO, where the ratio of the peak intensities of C1s and O1s can be used to determine the oxygen content in those graphene derivatives. For instance, the ratio was 2.35 for GO and 5.56 for ERGO material corroborating with the decrease of the concentration of oxygen groups in the carbon material. Rugosity was verified using square mean roughness (RMS) parameter obtained by AFM images and the values for unmodified GCE and ERGO surfaces were 14.20 and 19.96 nm, respectively. EIS measurements were also evaluated for bare and ERGO modified GCE, the values obtained for charge transfer resistance were 0.410 and 0.012 kΩ, respectively, indicating that the modified electrode provides a better electrochemical performance. The ERGO electrode was used as a sensor for furosemide (FUR) quantification, a diuretic drug for several treatments in human and veterinary medicine [2]. Flow injection analysis (FIA) with amperometric detection was used to quantify furosemide concentration in pharmaceutical formulations. Under the optimized conditions, the analytical parameters were 0.36 μmol L-1 and 2.4% (n=13) to LOD and repeatability, respectively. Two pharmaceutical samples were analyzed and demonstrated a good correlation between the FUR concentrations found by our method with the labeled value.