Abstract
Indigo carmine (IC) is an organic salt used as a colorant in food industries and in various pharmacological industries. The consumption of IC has numerous adverse effects on human health and its detection is of great importance. In this work, cyclic voltammetric (CV) analysis of IC was performed by developing an electropolymerized niacin modified carbon paste electrode (PNNMCPE). The morphological features of the bare carbon paste electrode (BCPE) and the PNNMCPE were studied through field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS) and energy-dispersive X-ray spectroscopy (EDXS). The electro-active surface area was calculated to be 0.032 cm
2
for PNNMCPE and 0.014 cm
2
for BCPE. An increase in the active surface area of the modified electrode resulted in the enhanced current sensitivity. The influence of electrolyte pH was analyzed and the obtained results indicated that the oxidation of IC on the PNNMCPE is associated with equal number of electrons and protons. The study of the impact of scan rate on the peak current and peak potential shows that the electrode surface shows adsorption controlled kinetics. The electro catalytic activities of BCPE and PNNMCPE towards IC were examined using CV in phosphate buffer solution (PBS). Under optimal experimental conditions, the designed electrode demonstrated a considerably low limit of detection (LOD) of 3.39 × 10
–7
M and low limit of quantification (LOQ) of 11.30 × 10
–7
M. The fabricated sensor showed high level of selectivity towards IC detection in the presence of common interfering metal ions and certain vitamins. Simultaneous analysis of IC was carried out in the presence of methyl orange (MO) with convincing results. The prime attributes such as reproducibility, stability and repeatability of the modified sensor were observed to a significant extent. The practicality of the modified sensor was substantiated by analyzing the presence of IC in candy coated chocolates and tap water samples. It is quite apparent from the outcome of the current work that the developed PNNMCPE is a novel, reliable, affordable and efficient sensor in the quantification of IC in food and water samples.