Improving the electrochemical response of furosemide by drop casting chemically reduced graphene oxide onto glassy carbon electrodes

Furosemide is a popularly used antihypertensive medicine due to its diuretic properties. It is also considered doping agent (since it can mask the use of others anabolic compounds), being almost entirely excreted in urine in its unaltered form (65-70%), leading to a highly possible occurrence in natural waters1. The objective of this work was to evaluate the possibility of using the glassy carbon electrode (GCE) modified with chemically reduced graphene oxide (CRGO) as a sensor for the furosemide amperometric determination using batchinjection analysis (BIA). Cyclic voltammograms were carried out under different acidic conditions (pH 3-9) using Britton-Robinson (BR) buffer. Other supporting electrolytes at the same optimum pH were also assessed such as phosphate and acetate buffers. At the best found condition, it could be observed an improvement on current signal intensity for furosemide using acetate buffer pH 5 with the GCE-CRGO (Fig. 1). Mass transport studies suggested a diffusional process, minimizing the need for mechanically stirring when using the BIA system. BIA parameters with amperometric detection were studied and optimized. Hydrodynamic voltammograms showed highest current intensity at +1.0 V. Repeatability study was performed by two different concentrations (1 and 10 μmol L-1) leading to satisfactory relative standard deviations (DPR, lower than 5%). A linear range from 1 to 600 μmol L-1, with good linearity (R2> 0.99) was reached, being the limit of detection (LOD) calculated as 0.82 μmol L-1. Possible application in biological fluids and natural waters will be evaluated.