** Authors:**
ZEINAB DERIS FALAHIEH, MEHDI JALALI, MOHAMMAD ALIMORADI

** Abstract: **
Cyclic voltammetry (CV) was performed on tamoxifen (tam) using different electrodes and in various acidic electrolytes containing 10% v v$^{-1}$ methanol (MeOH). Tam oxidation was found to be most favorable using 0.1 mol L$^{-1}$ H$_{2}$SO$_{4}$. To investigate the mechanism, we performed chronoamperometry, CV at different scan rates, differential pulse anodic voltammetry (DPAV), and electrochemical impedance spectroscopy on tam-covered glassy carbon electrodes (GCEs). The electrode area, diffusion coefficient, and surface concentration ($\Gamma )$ of tam were calculated to be 0.062 cm$^{2}$, 3.65 $\times $ 10$^{-6}$ cm$^{2}$ s$^{-1}$, and 3.2 $\times $ 10$^{-10}$ mol cm$^{-2}$ respectively. Then the effects of different parameters on the DPAV were optimized. The best conditions were 2.5% v v$^{-1}$ cMeOH, 0.1 mol L$^{-1}$ H$_{2}$SO$_{4}$, deposition potential 0.4 V, deposition time 30 s, and GCE rotating rate 400 rpm. Therefore, the calibration curve was plotted in the range of 0.5 to 5 $\mu $g mL$^{-1}$. The limits of detection and quantitation (LOD and LOQ) were found to be 0.008 and 0.025 $\mu $g mL$^{-1}$, respectively. The relative bias and standard deviation of 2 $\mu $g mL$^{-1}$ tam were estimated to be 5% (n = 5) and 2.3%, respectively. Finally, the proposed method was successfully employed for the determination of tam in real samples.

** Keywords: **
Tamoxifen, differential pulse anodic voltammetry, glass
carbon electrodes, serum analysis

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