Electroanalysis最新文献

17β-estradiol (E2) is the main female sex hormone widely found in pharmaceutics indicated for contraception and replacement therapy. Because this hormone is secreted by the body and contaminates the aquatic environment, it is considered an important organic pollutant to monitor due to its action on the human body as an endocrine disruptor. Therefore, the development of rapid, sensitive, precise, and portable methods is relevant for its quantification “in situ” in different matrices. In this context we propose the determination of E2 using a fast low-cost system composed of a graphite-acrylonitrile butadiene styrene (coated on 3D-printed ABS substrate) electrode assembled in a novel user-friendly 3D-printed batch injection analysis system with amperometric detection (BIA-AD). The best electrochemical behavior was obtained in 0.04 mol L⁻¹ Britton-Robinson buffer (pH 3.0) in which an irreversible oxidation was noted at +0.85 V. Under the optimized conditions of BIA-AD (detection potential = +1.1 V, injection volume = 100 µL, dispensing rate = 142 µL s⁻¹), a sensitivity of 0.154 µA µmol⁻¹L, a linear range of 0.1–7.0 µmol L⁻¹, an experimental LOD of 0.1 µmol L⁻¹, and an analytical frequency of 240 injections per hour were obtained. Good precision was reached for sequential injections of E2 at three concentration levels (8.6%, 3.2%, and 5.0% for 0.5, 3.0, and 6.0 µmol L⁻¹, respectively). Moreover, good interelectrode reproducibility was reached (RSD = 5.5%; n = 4), which confirms good manufacturing efficiency. The method was applied for the determination of E2 in pharmaceutical sample and river water. The results found in a pharmaceutical sample were statistically similar to the obtained by a UV–vis spectrophotometric method. The value found in river water was below the experimental LOD. Thus, this sample was fortified with different concentrations of E2, obtaining recoveries between 100% and 116%, which confirms the good accuracy of the method. The proposed BIA-AD is promising for the fast on-site determination of E2 in different matrices.

Considering the importance of antioxidants in food and medical industries, the accurate evaluation of their reactivity is of capital importance. In this work, a new electrochemical approach based on the cupric reducing antioxidant capacity (CUPRAC) is proposed for the accurate evaluation of antioxidant properties. The electrochemical behavior of the complex ([Cu(Nc)₂]²⁺) obtained from the reaction between copper(II) and neocuproine (Nc) used in the CUPRAC method was studied to identify the ideal Cu/Nc molar ratio. The Cu/Nc ratio of 4/3, usually used in the CUPRAC method, was not suitable because of the partial reaction of Nc with Cu(II). A more appropriate Cu/Nc molar ratio of 1/7 was experimentally determined by voltammetry at a stationary or rotating electrode. With this molar ratio, [Cu(Nc)₂]²⁺ presents a fast and monoelectronic system controlled by diffusion. This allowed antioxidant properties determination by chronoamperometry, by following the [Cu(Nc)₂]²⁺ reduction current as a function of the tested antioxidant. Ascorbic acid and Trolox used in this study as model antioxidants showed inhibition concentrations values (IC₅₀) very close to the expected theoretical values. These results are proof that the developed electrochemical method is accurate and allows a fast and efficient evaluation of antioxidant properties while minimizing interferences encountered using spectrophotometric methods.

Considering the importance of antioxidants in food and medical industries, the accurate evaluation of their reactivity is of capital importance. In this work, a new electrochemical approach based on the cupric reducing antioxidant capacity (CUPRAC) is proposed for the accurate evaluation of antioxidant properties. The electrochemical behavior of the complex ([Cu(Nc)₂]²⁺) obtained from the reaction between copper(II) and neocuproine (Nc) used in the CUPRAC method was studied to identify the ideal Cu/Nc molar ratio. The Cu/Nc ratio of 4/3, usually used in the CUPRAC method, was not suitable because of the partial reaction of Nc with Cu(II). A more appropriate Cu/Nc molar ratio of 1/7 was experimentally determined by voltammetry at a stationary or rotating electrode. With this molar ratio, [Cu(Nc)₂]²⁺ presents a fast and monoelectronic system controlled by diffusion. This allowed antioxidant properties determination by chronoamperometry, by following the [Cu(Nc)₂]²⁺ reduction current as a function of the tested antioxidant. Ascorbic acid and Trolox used in this study as model antioxidants showed inhibition concentrations values (IC₅₀) very close to the expected theoretical values. These results are proof that the developed electrochemical method is accurate and allows a fast and efficient evaluation of antioxidant properties while minimizing interferences encountered using spectrophotometric methods.

In this study, we evaluated the preparation conditions, stability, and durability of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-modified glassy carbon (GC) electrodes prepared using electrolytic polymerization in an aqueous solvent, and examined the applicability of the electrodes as electrochemical sensors for pharmaceutical analysis. First, we synthesized a TEMPO-substituted phenol (2-PH-TEMPO) and examined the conditions for its efficient immobilization on an electrode using the electrolytic polymerization method in an aqueous solvent. The TEMPO-modified GC electrode showed high stability and durability in a low-concentration substrate environment and effectively functioned as an electrolytic oxidation catalyst for ethanol, a compound with a hydroxyl group. In an analysis of pharmaceuticals, a high oxidative response was obtained for lidocaine, clarithromycin, and azithromycin, which have tertiary amines or multiple oxidizable hydroxyl groups, suggesting that the electrode can function as a highly sensitive electrochemical sensor. The use of this modified electrode enables quantification in the clinical concentration range of vancomycin, and it is expected to be applied to rapid and accurate pharmaceutical concentration measurements in therapeutic drug monitoring. These results suggest that TEMPO-modified GC electrodes are useful as stable and sensitive electrochemical sensors in the fields of pharmaceutical analysis and biosensors, and are expected to contribute to the development of quantitative electrochemical methods.

In this study, we evaluated the preparation conditions, stability, and durability of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-modified glassy carbon (GC) electrodes prepared using electrolytic polymerization in an aqueous solvent, and examined the applicability of the electrodes as electrochemical sensors for pharmaceutical analysis. First, we synthesized a TEMPO-substituted phenol (2-PH-TEMPO) and examined the conditions for its efficient immobilization on an electrode using the electrolytic polymerization method in an aqueous solvent. The TEMPO-modified GC electrode showed high stability and durability in a low-concentration substrate environment and effectively functioned as an electrolytic oxidation catalyst for ethanol, a compound with a hydroxyl group. In an analysis of pharmaceuticals, a high oxidative response was obtained for lidocaine, clarithromycin, and azithromycin, which have tertiary amines or multiple oxidizable hydroxyl groups, suggesting that the electrode can function as a highly sensitive electrochemical sensor. The use of this modified electrode enables quantification in the clinical concentration range of vancomycin, and it is expected to be applied to rapid and accurate pharmaceutical concentration measurements in therapeutic drug monitoring. These results suggest that TEMPO-modified GC electrodes are useful as stable and sensitive electrochemical sensors in the fields of pharmaceutical analysis and biosensors, and are expected to contribute to the development of quantitative electrochemical methods.

This study proposed a new method for the direct and reagent-free fabrication of laser-induced graphene (LIG)-gold (Au–LIG) nanocomposite electrodes on a polyimide (PI) film using a commercially available, low-cost do-it-yourself (DIY) blue laser system for the first time. The one-step fabrication of Au–LIG nanocomposite was achieved by simply irradiating a PI film previously covered with gold leaves using a blue laser. Surface analysis and electrochemical oxidation of glucose revealed the formation of Au–LIG nanocomposites on the electrodes. Electrochemical sensitivity of the Au–LIG electrode against glucose in the concentration range from 0.1 to 50 mM was 153.4 µA/cm²/mM-glucose, and its limit of detection was 45.5 µM. This simple and cost-effective DIY blue laser system is expected to significantly contribute to the low-cost mass production of high-performance chemical sensors.

Electrochromic devices (ECDs) have been extensively studied worldwide due to their promising applications in various fields. To the best of our knowledge, all previously reported ECDs are exclusively driven by direct current (DC), which has been the conventional approach in electrochromic research. In this article, we propose that the ECD driven by alternating current (AC) should be testified. The ECDs were sandwiched in all-in-one mode using 1,1′-dibenzyl-4,4′-dipyridine dichloride as electrochromic chromophore. The electrochromic performance of the as-AC-driven ECDs was examined as a function of AC frequency from 0.1 to 1000 Hz. It is found that electrochromic based on dibenzyl viologen can work driven by AC, but with some differences from that by DC. The optical contrast is directly proportional to the logarithm value of AC frequency in the range from 0.1 to 1000 Hz, which suggests that the AC-driven ECD may potentially be useful as a visual indicator for AC frequency.

In this work, an amperometric pyruvate-sensitive biosensor was developed and optimized. A platinum disk electrode was used as an amperometric transducer. The bioselective element of the biosensor is based on the pyruvate oxidase enzyme immobilized with PVA-SbQ polymer by photopolymerization. The optimal immobilization conditions (enzyme and photopolymer concentrations, duration, and intensity of photopolymerization) were selected. The optimal concentrations of cofactors and cosubstrates (phosphate ions, thiamine pyrophosphate, and magnesium ions (Mg²⁺) were chosen to ensure the best sensitivity of the developed biosensor to pyruvate. After optimizing the design of the bioselective element and the immobilization process, the reproducibility of the biosensor manufacturing procedure was investigated (RSD = 12.5%). To assess the prospects of the developed biosensor, its main analytical characteristics were analyzed. The linear range of the biosensor was from 10 to 500 μM pyruvate, and the sensitivity was 66 nA/mM. The minimum detection threshold was 1.57 μM pyruvate. The obtained data indicate the technical feasibility and prospects of using the developed biosensor for determining the concentration of pyruvate in real multicomponent biological samples.

Electrochromic devices (ECDs) have been extensively studied worldwide due to their promising applications in various fields. To the best of our knowledge, all previously reported ECDs are exclusively driven by direct current (DC), which has been the conventional approach in electrochromic research. In this article, we propose that the ECD driven by alternating current (AC) should be testified. The ECDs were sandwiched in all-in-one mode using 1,1′-dibenzyl-4,4′-dipyridine dichloride as electrochromic chromophore. The electrochromic performance of the as-AC-driven ECDs was examined as a function of AC frequency from 0.1 to 1000 Hz. It is found that electrochromic based on dibenzyl viologen can work driven by AC, but with some differences from that by DC. The optical contrast is directly proportional to the logarithm value of AC frequency in the range from 0.1 to 1000 Hz, which suggests that the AC-driven ECD may potentially be useful as a visual indicator for AC frequency.

In this work, an amperometric pyruvate-sensitive biosensor was developed and optimized. A platinum disk electrode was used as an amperometric transducer. The bioselective element of the biosensor is based on the pyruvate oxidase enzyme immobilized with PVA-SbQ polymer by photopolymerization. The optimal immobilization conditions (enzyme and photopolymer concentrations, duration, and intensity of photopolymerization) were selected. The optimal concentrations of cofactors and cosubstrates (phosphate ions, thiamine pyrophosphate, and magnesium ions (Mg²⁺) were chosen to ensure the best sensitivity of the developed biosensor to pyruvate. After optimizing the design of the bioselective element and the immobilization process, the reproducibility of the biosensor manufacturing procedure was investigated (RSD = 12.5%). To assess the prospects of the developed biosensor, its main analytical characteristics were analyzed. The linear range of the biosensor was from 10 to 500 μM pyruvate, and the sensitivity was 66 nA/mM. The minimum detection threshold was 1.57 μM pyruvate. The obtained data indicate the technical feasibility and prospects of using the developed biosensor for determining the concentration of pyruvate in real multicomponent biological samples.