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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 cm2 for PNNMCPE and 0.014 cm2 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. [ABSTRACT FROM AUTHOR]

Binder-free and efficient electrochemical sensing of levofloxacin (LF) was successfully developed based on the nitrogen-doped carbon nanodots (NCNDs). The NCNDs were synthesized by hydrothermal carbonation (180°C for 12 h), and the heteroatom was embedded in aqueous solution of ammonia (NH3). Spectral and microscopic characteristization techniques were used to analyze the topological, crystallinity, and chemical binding behavior of synthesized biomass functional material. HR-TEM image revealed a uniform spherical dot (2.96 nm), and superior quantum yield efficiency (0.42 Φ). The NCNDs was drop coated on a glassy carbon electrode (GCE) and electrochemical sensing of LF was performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric i-t curve in phosphate-buffered saline (PBS; pH = 7.0). The NCNDs modified electrode showed a sharp oxidation peak at +0.95 V (vs. Ag/AgCl) with a four-fold higher current response than the bare GC electrode. The NCNDs/GCE surface not only increases the current response, but has lower detection potential, and facilitates electron transfer reaction. Under optimized working parameters, the NCNDs/GCE showed wide linear concentrations range from 200 nM to 2.8 mM and a low detection limit (LOD) of 48.26 nM (S/N = 3). The electrode modified with NCNDs has high electrochemical sensing stability (RSD = 1.284 ± 0.05% over 5 days), and superior reproducibility (RSD = 1.682 ± 0.06% (n = 3)). Finally, the NCNDs modified GC electrode was successfully applied to quantify the concentration of LF in drug and river water samples with acceptable recovery percentages of 96.60–99.20% and 97.20–99.00% (n=3), respectively. [ABSTRACT FROM AUTHOR]

B Correction: Microchimica Acta (2023) 190:242 b https://doi.org/10.1007/s00604-023-05804-0 In this article, the second affiliation was not appended and the corrections in Acknowledgments section was not carried out. Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. [Extracted from the article]

The current research focused on designing a simple, inexpensive, and green electrochemical sensor for the sensitive estriol hormone (ETL) detection. To achieve this, a bare carbon nanotube paste electrode (BCNTPE) and electrochemically polymerized L-arginine (ARN)-modified carbon nanotube paste electrode (MCNTPE) were developed. The prepared electrochemical sensor was characterized using various techniques, such as field-emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV) methods. The investigation of the electrochemical oxidation nature of ETL in a supporting electrolyte of phosphate buffer solution (PBS) with pH 6.5 was carried out using a modified electrode (PARNMCNTPE) having superior electrocatalytic activity and more electrochemical active spots than the BCNTPE. Significant parameters like the impact of the pH of PBS, potential scan rate, and ETL concentration on the electrochemical behavior of ETL at the surface of the PARNMCNTPE were investigated. The potential scan rate and pH of PBS variation influence that the ETL oxidation at the PARNMCNTPE surface proceeded via pH-dependent and adsorption-controlled reaction pathways. The PARNMCNTPE senses ETL in the range from 2 × 10–6 to 90 × 10–6 M with a lower limit of detection (LOD) of 3.25 × 10–7 M and a limit of quantification (LOQ) of 10.84 × 10–7 M. The PARNMCNTPE shows decent stability, repeatability, and reproducibility for the detection of ETL. Additionally, the PARNMCNTPE analytical applicability was studied for ETL detection in medicinal samples. [ABSTRACT FROM AUTHOR]