A simple electrochemical sensor for nicotine (NIC) detection was performed. The sensor based on a glassy carbon electrode (GCE) was modified by (1,2-naphthoquinone-4-sulphonic acid)(Nq) decorated by graphene oxide (GO) nanocomposite. The synthesized (GO) nanosheets were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), FT-IR, and UV-Visible Spectroscopy. The insertion of Nq with GO nanosheets on the surface of GCE displayed high electrocatalytic activity towards NIC compared to the bare GCE. NIC determination was performed under the optimum conditions using 0.10 M of Na₂SO₄ as a supporting electrolyte with pH 8.0 at a scan rate of 100 mV/s using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). This electrochemical sensor showed an excellent result for NIC detection. The oxidation peak current increased linearly with a 6.5–245 µM of NIC with R² = 0.9999. The limit of detection was 12.7 nM. The fabricated electrode provided satisfactory stability, reproducibility, and selectivity for NIC oxidation. The reliable GO/Nq/GCE sensor was successfully applied for detecting NIC in the tobacco product and a urine sample.

In this work, an accurate, highly sensitive, and economical electrochemical sensor based on a carbon paste electrode modified by Ca₂CuO₃ nanostructure (Ca₂CuO₃ NS) was constructed using Eggshell waste recycling as a cheap source of calcium. The Ca₂CuO₃ NS was analyzed using FTIR, SEM, and XRD measurements. The synthesized nanomaterials utilized for the first time to enhance the electrocatalytic efficiency of carbon paste electrode (CPE) toward fluoroquinolones antibiotics ofloxacin (OFL) and ciprofloxacin (CIP), The drugs used to treat pneumonia caused by COVID-19. The synthesized Ca₂CuO₃ NS dramatically enhanced the anodic peak response of CPE toward both drugs compared to the unmodified one and other modified electrodes. The simultaneous detection of the two antibiotics was performed in the linear range of 0.09–1.0 μM for OFL and 0.05–0.8 μM for CIP with the LOD of 0.027 μM and 0.012 μM, respectively. The suggested method was applied successfully to determine OFL and CIP in real samples.

HEREIN, Multi Walled Carbon Nano-tubes a fabrication and application of a novel sensor of carbon paste electrode modified by silica gel/MWCNTs for the determination of salicylic acid (SA) by different voltammetric techniques such as Linear Sweep, Cyclic and Square Wave Voltammetry. The electrochemical behavior of SA has been investigated and the optimum experimental conditions such as the effect of supporting electrolyte, pH and scan rate on the anodic peak of SA was determined. Square Wave Voltammetry (SWV) was employed to determine SA, where the important parameters such as frequency were achieved. Moreover, the results showed that modified electrode exhibited excellent electrocatalytic activity towards the oxidation of SA. The results showed irreversible process with one oxidation peak of SA at the surface of modified electrode and the overpotential of SA decreased significantly compared with that at the bare carbon paste electrode (CPE). This electrochemical sensor shows an excellent performance for detecting SA with a detection limit and limit of quantification were 0.9 x 10(-9) M and 2.99 x 10(-9) M respectively. In addition, the peak currents increased linearly in the concentration range of 3.0-70 nM. The results showed also, the fabricated sensor was successfully applied to the detection of SA in tomato with good recovery ranging from 96.60 to 103%, Moreover, the proposed electrode revealed good reproducibility and stability, with standard deviation (S.D.) 2.3% for eight successive measurements of SA.