A novel electrochemical sensor was fabricated by simply screen printing reduced graphene oxide (rGO) paste on F-doped tin oxide (FTO) (rGO-SP-FTO) followed by sintering at 450 • C in Argon and employed for detecting dopamine (DA) and uric acid (UA) simultaneously. The rGO film was characterized by using Raman spectroscopy, field emission scanning electron microscope (FE-SEM), and Fourier transform infrared spectroscopy (FTIR). The surface sensing features of rGO-SP-FTO were studied with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The rGO-SP-FTO electrode exhibited foremost sensitivity in simultaneous detection of DA and UA without any interference from ascorbic acid (AA). The rGO-SP-FTO electrode showed a good linear response in the range of 0.5-50.0 μM and 5.0-300 μM with detection limits (S/N = 3) of 0.07 μM and 0.39 μM for DA and UA, respectively. The interactions between screen printed rGO with FTO electrode and their influence on how rGO-SP-FTO electrode interacted with UA, DA, and AA were analyzed from experimental observations. The rGO-SP-FTO electrode was able to detect DA in dopamine hydrochloride injection (DAI) and UA in urine sample effectively. Moreover, the designed electrochemical sensor exhibited excellent stability and reproducibility.

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A simple, highly sensitive and inexpensive electrochemical method was established using an activated glassy carbon electrode (AGCE) in an acidic condition for the determination of ranitidine (RT) and metronidazole (MT) simultaneously at a low potential range. The AGCE was characterized using various techniques such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and morphology was studied through field‐emission scanning electron microscope (FE‐SEM). The AGCE exhibited an electrocatalytic behavior towards the reduction of RT and MT in 0.5 M acidic solution. Both CV and DPV responses for the mixture of RT and MT gave well‐resolved peaks at low potential. Analysis of these experiments helps us to predict interactions that took place on the surface of AGCE and RT and MT with each other for having different types of functional groups. Furthermore, AGCE also promoted the electron transfer process. The linear dynamic range of MT and RT was 0.5–580 μM and 0.5–500 μM, respectively with the regression coefficient 0.99. The detection limit (S/N=3) calculated for MT and RT was 0.062 μM and 0.13 μM, respectively. Decent results were obtained from the reproducibility and stability test. The performance of the sensor was evaluated for the possible interferences which show high selectivity. Additionally, the real sample analysis was carried out to understand our sensor‘s applicability in real life.