The electrocatalytic performance of carbon paste electrode modified with ferrocene-derivative (ethyl 2-(4-ferrocenyl[1,2,3]triazol-1-yl)acetate, EFTA) , CeO–ZnO nanocomposite as well as ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) (CeO–ZnO/ILFCPE) was investigated for simultaneous detection of penicillamine and tryptophan. According to the results, the penicillamine oxidation on the surface of fabricated carbon paste electrode at an optimal pH of 7.0 was observed less positive at 320 mV potential compared to unmodified electrode. The penicillamine oxidation showed the electron transfer coefficient (α) of 0.58 and diffusion coefficient (D) of 1.2 × 10–6 cm2/s. The linear dynamic range was also calculated to be between 0.02–25.0 μM, and the limit of detection (LOD) was 10.0 nM. High selectivity and satisfactory reproducibility found for the modified carbon paste electrode suggest the possibility of analytical applications. The application of the synthesized sensor was examined in real specimens for detection of penicillamine and tryptophan.