A glassy carbon electrode modified with reduced graphene oxide for sensitive determination of bumetanide in urine at levels required for doping analysis

The dopant bumetanide (BMT) was banned by the World Anti-Doping Agency. The authors describe a voltammetric sensor for the determination of BMT in urine that is based on the use of a glassy carbon electrode modified with reduced graphene oxide (GCE/rGO). The GCE/rGO was prepared by electrodeposition from a solution of GO. The oxidation of BMT occurs best at +0.75 V in the GCE/rGO with an approximately 13-fold gain in the anode current compared to a conventional GCE. The oxidation mechanism was investigated by means of electrolysis, while the analysis of the products was carried out via the LC–MS/MS. Under optimized conditions (scan rate 100 mV s −1 ; pH 4.0; accumulation time 25 s) and by using linear sweep adsorptive stripping voltammetry, the response covers the 0.26 to 50 μmol L −1 BMT concentration range. The detection limit is 75 nmol L −1 . The sensor was successfully applied and validated by LC–MS/MS analysis of spiked urine sample. Graphical abstract Schematic of a glassy carbon electrode modified with reduced graphene oxide by electrodeposition using a solution of graphene oxide. The modified electrode showed an improvement in the electron transfer kinetics and a large increase in the analytical signal.