A sensitive and selective sensor for dopamine determination based on a molecularly imprinted electropolymer of o-aminophenol

A simple and reliable method was proposed for preparing a selective dopamine (DA) sensor based on a molecularly imprinted electropolymer of o-aminophenol. The sensor is selective for the determination of DA in the presence of high concentrations of ascorbic acid (AA), with a maximum molar ratio of 1/1000. The molecular imprinted (MIP) sensor was tested by cyclic voltammetry (CV) as well as differential pulse voltammetry (DPV) to verify the changes in oxidative currents of ferricyanide. In optimized conditions, DA at concentrations of 2 × 10⁻⁸ to 0.25 × 10⁻⁶ mol/L could be determined with a detection limit of 1.98 × 10⁻⁹ mol/L (S/N = 3). The MIP sensor showed high selectivity, sensitivity, and reproducibility. Determination of DA in simulated samples of dopamine hydrochloride showed good recovery.     

A new method for characterizing the growth and properties of polyaniline and poly(aniline-co-o-aminophenol) films with the combination of EQCM and in situ FTIR spectroelectrochemisty

A new method of in situ piezoelectric Fourier transform infrared (FTIR) spectroelectrochemisty, i.e., the combination of in situ FTIR and electrochemical quartz crystal microbalance (EQCM), was developed to study the electropolymerization of aniline and aniline-co-o-aminophenol, to investigate the properties of the polymers in 0.2 M HClO₄. The piezoelectric electrochemical studies showed that the copolymerization process was changed in the presence of o-aminophenol and the copolymer exhibited different electrochemical behaviors from polyaniline and poly-o-aminophenol. The effects of the molar ratio of o-aminophenol on the copolymerization speed and the scan rate or pH values on the electroactivity of the copolymer were also investigated. The results suggested that the copolymer formed in the case of F = 0.1 had good stability and electroactivity than polyaniline at different pH values. The results obtained by the way of in situ piezoelectric FTIR spectroelectrochemisty indicated that the copolymerization process and the properties of the copolymer were different from that of polyaniline. The polymerization mechanisms and the structure of the two polymers were also different from each other. The copolymer formed through head-to-tail coupling of the two monomers via NH groups was a new polymer rather than a mixture of polyaniline and poly-o-aminophenol.     

The degradation of electrochemically polymerised poly (3-aminophenol) films in sodium hydroxide solutions for the production of microelectrode ensembles

Poly (3-aminophenol) films have been grown electrochemically from solutions of 3-aminophenol at pH 7. These pinhole free films passivate the electrode surface and are less than 10 nm thick. The films are stable in 1 M solutions of sulphuric acid. However, they are rapidly degraded in solutions of sodium hydroxide. It is demonstrated that initially the polymer removal results in the creation of an electrode that exhibits the characteristics of a microelectrode ensemble. However, as further polymer is removed these characteristics are lost and response of the electrode resembles that of a large planar electrode. This chemical treatment of poly (3-aminophenol) films allows for the cost-effective production of microelectrode ensembles.     

Voltammetric and spectroelectrochemical studies on 4-aminophenol at gold electrodes in aqueous and organic media

Voltammetric and UV-Vis spectroelectrochemical studies on 4-aminophenol (4-AP) at gold electrodes have been carried out in conventional electrochemical and in novel spectroelectrochemical cells. As base electrolytes acetonitrile with 10⁻² M tetrabutylammonium hexafluorophosphate as supporting electrolyte and acetate buffer (pH 4.6) solutions have been used. 4-AP was electrochemically oxidized at gold electrodes at potentials >+0.1 V in aqueous solutions and at potentials >+0.5 V in acetonitrile solutions. The formation of an oxidation product has been characterized in situ by UV-Vis spectroscopy in a novel optical thin-layer spectroelectrochemical cell.     

荧光法同时测定对硝基酚和对氨基酚

在ｐＨ１０～３０的ＨＣｌ介质中,荧光物质对氨基酚的激发波长和发射波长分别为２７１ｎｍ和３７１ｎｍ．当有对硝基酚共存时,用硼氢化钠将其还原为对氨基酚,可用荧光光度法同时测定两者的含量．对硝基酚和对氨基酚的检测限分别为０２７μｇ／ｍＬ和０３２μｇ／ｍＬ．样品加标回收率分别为对氨基酚：９５１％～１０１５％,对硝基酚：８９８％～１００５％．     

硝基苯选择加氢制对氨基苯酚

研究了以０ ．８ ％ Ｐｄ／ Ｃ 为催化剂,硫化物为助催化 剂, 在酸性介质中硝基苯选择 催化氢化合成对氨基苯酚的反应条件。该反应 最佳条 件为：氢气 的压力 ０ ．２ Ｍ Ｐａ , 催化剂 用量为 反应物 质量的 １ ．２ ％ ,助催化剂与催化剂用量摩尔比为０ ．６ ,硫酸溶液的质量分数为１２ ％ ,阳离子表面活性剂０ ．４ ｍ Ｌ,反应温度为（８５ ±１） ℃,反应时间为８０ ｍｉｎ 。研究 结果表明,选用易回收、低浓度 的０ ．８ ％ Ｐｄ／ Ｃ 催化剂,对硝基苯氢化反应具有较高的活性,通过 添加助催化剂可明显提高 反应的选择性。合成产品通过 Ｉ Ｒ、 Ｍ Ｓ 确认其结构,并通过滴定氨基值计算出硝基苯的转化率为９０ ％ 左右,产品的选择性达８０ ％ 。该工艺生产成本比传统工艺低,工业污染小,操作简便,收率高,为工业化生产提供理论依据     

Aqueous two-phase systems: a new approach for the determination of p-aminophenol

A new method has been developed for the spectrophotometric determination of p-aminophenol (PAP) in water, paracetamol formulations and human urine samples with a recovery rate between 94.9 and 101%. This method exploits an aqueous two-phase system (ATPS) liquid-liquid extraction technique with the reaction of PAP, sodium nitroprusside and hydroxylamine hydrochloride in pH 12.0, which produces the [Fe₂(CN)₁₀]¹⁰⁻ anion complex that spontaneously concentrates in the top phase of the ATPS (K[Fe₂(CN)₁₀]¹⁰⁻=97.7). The ATPS does not require an organic solvent, which is a safer and cleaner liquid-liquid extraction technique for the determination of PAP. The linear range of detection was from 5.00 to 500 μg kg⁻¹ (R ≥ 0.9990; n = 8) with a coefficient of variation of 2.11% (n = 5). The method exhibited a detection limit of 2.40 μg kg⁻¹ and a quantification limit of 8.00 μg kg⁻¹. The ATPS method showed a recovery that ranged between 96.4 and 103% for the determination of PAP in natural water and wastewater samples, which was in excellent agreement with the results of the standard 4-aminoantipyrine method that was performed on the same samples.     

Optimization of aqueous p-aminophenol degradation by external-loop airlift sonophotoreactor using response surface methodology

The combination of sonolysis and photolysis in the presence of hydrogen peroxide (H₂O₂) in a 7-L external-loop airlift sonophotoreactor was used to treat the aqueous solution of p-aminophenol. The central composite design (CCD) and response surface methodology (RSM) were employed to evaluate the interaction effects of the initial H₂O₂ concentration (x₁ = 100–900 mg/L), the ultrasonic power (x₂ = 25–65 W), the air flow rate (x₃ = 1–5 L/min), and the initial concentration of p-aminophenol (x₄ = 10–50 mg/L) on the p-aminophenol degradation and total organic carbon (TOC) reduction efficiencies as well as to optimize operating conditions. The coefficients of determination (R²) and adjusted-R² obtained from the analysis of variance (ANOVA) were 0.9900 and 0.9812 for the p-aminophenol degradation; and 0.9742 and 0.9516 for the TOC removal, respectively, ensuring a satisfactory adjustment of the quadratic regression model with experimental results. The linear, square, and interaction effects of x₁, x₂, x₃, and x₄ were also calculated. Genetic algorithm optimization was employed to maximize the mineralization efficiency. 79% TOC reduction efficiency after 90 min and 86.5% p-aminophenol removal efficiency after 30 min were achieved under recirculating batch mode at operating conditions of x₁ = 740 mg/L, x₂ = 65 W, x₃ = 5 L/min, and x₄ = 24 mg/L.     

Kinetic Behavior of Cobalt Nanoparticles Facilitated by Cationic Surfactant

In this report, spectrophotometric, kinetic, and structural analysis has been carried out for the formation of cobalt nanoparticles (CoNPs) using 4-aminophenol as reducing agent. The localized surface plasmon resonance band (SPR) of cobalt nanoparticles in the UV–vis spectrum is used to determine the rate of formation of cobalt nanoparticles and assess the beginning of the oxidation process. The effect of cobalt nitrate, 4-aminophenol and TTAB concentration was investigated on the growth rate of cobalt nanoparticles. CoNPs were characterized by means of UV–vis, field emission scanning electron microscope (FESEM), and energy dispersive spectroscopy (EDS). The data obtained in this work provide valuable information on the rate of reactions at the nanoscale.     

Electrosynthesis of poly(aniline-co-p-aminophenol) having electrochemical properties in a wide pH range

Copolymerization of aniline and p-aminophenol in aqueous sulfuric acid solutions was electrochemically performed using cyclic voltammetry on platinum electrodes. The monomer concentration ratio can strongly affect the copolymerization rate and electrochemical property of the copolymer. The optimum conditions for the copolymerization are that the potential sweep covers the −0.20 to 0.95 V (vs. SCE) potential range, and that a solution contains 0.18 M aniline, 0.02 M p-aminophenol and 0.50 M H₂SO₄. A resulting copolymer synthesized under the optimum conditions has a good electrochemical activity in 0.50 M solutions of Na₂SO₄ with pH ≤ 10.0. IR and XPS spectra indicate that -OH groups and SO₄²⁻ ions are contained in the resulting copolymer. The SEM images reveal that the microstructure of the copolymer depends on the monomer concentration ratio during the electrolysis.