Analysis of Indigo Carmine by Polymer-Modified Biosensor Using Electro-Polymerization Technique

Indigo carmine (IC) was used as an analyte and a layer of film with serine as the functional monomer was electropolymerized to create a poly(serine)-modified carbon paste electrode (PSMCPE). Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and electrochemical technology, in that order, were used to characterize the morphology, structure, and electrochemical characteristics of the PSMCPE. Experimental parameters including the reagent molar ratio, the number of electropolymerization cycles, scan rate, and electrolyte pH level, were methodically optimized during the sensor’s fabrication. Under optimal conditions, cyclic voltammetry (CV) and differential pulsed voltammetry (DPV) were used for IC detection. The PSMCPE response current for IC exhibited a significant enhancement compared to that of the bare carbon paste electrode (BCPE). The linear range of IC measured by DPV was determined to be 0.2–3.5 μM, with the corresponding lower detection limit (LOD) 1.3211 × 10⁻⁷ M and lower limits of quantification (LOQ) 4.403 × 10⁻⁷ M. The modified electrode confirmed outstanding repeatability, reproducibility, and stability. Finally, the real-time application of the sensor was confirmed by investigating IC in a water sample, when good IC recovery was observed.