Multiwalled Carbon Nanotubes/4,4′‐dihydroxybiphenyl Nanolayered Composite for Voltammetric Detection of Phenol

Eco-friendly spectrophotometric methods for concurrent analysis of phenol, 2-aminophenol, and 4-aminophenol in ternary mixtures and water samples: assessment of environmental sustainability

Recently, there has been a high demand for green procedures in analytical chemistry, particularly those utilizing eco-friendly solvents. In this context, three feasible derivative UV spectrophotometric methods namely, derivative ratio-zero crossing spectra (DRZCS), double divisor ratio spectra (DDRS), and successive derivative subtraction coupled with constant multiplication (SDS-CM) were developed to quantify a ternary mixture of phenol (P), 2-aminophenol (2-AP), and 4-aminophenol (4-AP) in real water samples simultaneously, using ethanol as a solvent. The established methods demonstrated a good linear range, covering 2-60 μg mL-1 for P and 2-50 μg mL-1 for 2-AP and 4-AP, in all approaches with a high correlation coefficient (R2 ≥ 0.9995). In compliance with ICH guidelines, the methods exhibited acceptable precision and accuracy, as indicated by good spike recovery with low relative standard deviations. The eco-friendliness of the UV spectrophotometric approach was assessed using analytical eco-scale (AES), analytical greenness (AGREE), and analytical greenness metrics for sample preparation (AGREEprep). These evaluations confirmed the eco-friendliness of the proposed methods in terms of solvents, energy consumption, and waste generation. The proposed procedure proved to be efficient in quantifying each component in laboratory-synthesized mixtures and real water samples, thanks to its simplicity, accuracy, sensitivity, and cost-effectiveness.

Iodine/iodide-doped polymeric nanospheres for simultaneous voltammetric detection of p-aminophenol, phenol, and p-nitrophenol

A sensor was developed for the first time based on polydopamine nanospheres doped with I₂, I^-, and IO₃^- species (PDA-Iodine), to determine the concentration of p-aminophenol (p-AP), phenol (Ph), and p-nitrophenol (p-NP) simultaneously. These polymeric nanospheres were successfully characterized using a variety of techniques including field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, Raman spectroscopy, and X-ray diffraction analysis. A carbon paste electrode was modified with the PDA-Iodine (CPE/PDA-Iodine). Because of the electrocatalytic activity of DA/DQ, I₂ and I^- species (in the structure of PDA-Iodine), CPE/PDA-Iodine shows enhancement in the electrooxidation peak currents as well as slight negative shift in peak potentials of p-AP, Ph, and p-NP compared with a bare carbon paste electrode. Under optimal experimental conditions, the linear calibration plots are linear in the ranges 0.5-120 μM for p-AP, 0.7-120 μM for Ph, and 1.0-100 μM for p-NP with limits of detection of 30, 40, and 80 nM for p-AP, Ph, and p-NP, respectively (S/N = 3). To prove the performance of the method, the repeatability of the signals of CPE/PDA-Iodine was evaluated and the RSD values obtained were 2.9%, 3.2%, and 3.1% for p-AP (45 µM), Ph (40 µM), and p-NP (40 µM), respectively. The CPE/PDA-Iodine is a promising new sensor for sensing p-AP, Ph, and p-NP simultaneously in tap and river water sample and the values of recoveries for spiked samples were in the range 94.0-104.4%.