Ion amperometry at the interface between two immiscible electrolyte solutions in view of realizing the amperometric ion-selective electrode

This article reviews the development in ion amperometry at the interface between two immiscible electrolyte solutions (ITIES) in view of realizing the amperometric ion-selective electrode (ISE). The concept of polarizability of ITIES in a multi-ion system is outlined. Principle aspects of ion amperometry at ITIES are discussed including the use of amperometry as a tool for the clarification of the ion sensing mechanism, and for determining the concentrations of ions in the solution. The reference is made to recent amperometric measurements at the supported liquid membrane (SLM) and polymer composite liquid membranes (PCLM), which, together with the micro-hole supported ITIES, appear to be particularly suitable for realization of the amperometric ISE.     

Amperometric Immunosensor for Rapid Detection of Honeybee Pathogen Melissococcus Plutonius

European foulbrood (EFB) is a honeybee larvae disease caused by a bacterium Melissococcus plutonius. An amperometric immunosensor based on a sandwich assay was developed for rapid point‐of‐care detection of this pathogen. An in‐house made anti‐Melissococcus antibody was immobilized to a gold surface of a screen‐printed sensor via self‐assembled monolayer of cysteamine activated with glutaraldehyde. The direct impedimetric detection of captured microbial cells was tested, however, a better performance was obtained after the formation of sandwich with the peroxidase‐labeled antibody in the amperometric mode. The label‐free assay was limited by higher non‐specific binding. The limit of detection of the immunosensor was 6.6×10⁴ CFU mL^?1 (colony‐forming units) with wide linear range between 10⁵ CFU mL^?1 and 10⁹ CFU mL^?1. The whole analysis was completed within 2 h, which is shorter compared to common laboratory diagnostic tools, such as enzyme‐linked immunosorbent assay or polymerase chain reaction. Furthermore, atomic force microscopy was used for confirmation of the bacteria presence on the electrode surface. The developed immunosensor was successfully employed in the analysis of real samples of honeybees and larvae. The achieved results demonstrate the potential of the amperometric immunosensor for practical in‐field diagnosis of EFB, which can prevent infection spreading and connected losses of honeybee colonies.     

电化学方法检测非电活性气体二氧化碳的若干问题研究

就非电活性气体ＣＯ２检测所遇到的若干电化学问题，诸如ＣＯ２电还原和直接电流法测定、Ｏ２的干扰以及ＣＯ２和Ｏ２气体的同时检测等，进行了系统的研究．先后提出并建立了微电流法、耗尽电解除氧法、调制电位脉冲－电流／库仑法等电化学测量方法，最终实现了常温下ＣＯ２和Ｏ２气体的快速电化学方法联合检测，既消除了Ｏ２的干扰，又无需ＣＯ２在电极上直接还原．     

Sensitive Electrochemical Determination of NADH Using an Electrode Fabricated by Intercalation of Tetrabutylammonium Ions Into Graphite Electrode

In this study, we present a strategy for the specific electrochemical detection of NADH in human blood serums using modified electrode fabricated by intercalation of tetrabutylammonium ions (TBA⁺) into pencil graphite electrode (TBA⁺/PGE). In order to implement this protocol, a modification process in the potential range (−0.2) to (−2.75) V was performed in DMSO containing 0.1 M TBAP by CV method. The characterization processes of the prepared sensor were carried out using CV, EIS, FT-IR, XPS, and SEM methods. The electrode fabricated by intercalation of TBA⁺ was found to be able to analyze NADH at +0.32 V applied potential by the amperometric method. The LOD was detected as 0.46 μM. The analysis results of human blood serums which are taken from healthy individuals show that TBA⁺/PGE can be used for real samples. The results indicated that TBA⁺/PGE can be easily fabricated by one-step and one-pot electrochemical method and TBA⁺/PGE can be used as a potential sensor for the NADH determination.     

Electrochemical Determination of Pyrogallol at Conducting Poly(3,4‐ethylenedioxythiophene) Film‐Modified Screen‐Printed Carbon Electrodes

The electrochemical oxidation of pyrogallol at electrogenerated poly(3,4‐ethylenedioxythiophene) (PEDOT) film‐modified screen‐printed carbon electrodes (SPCE) was investigated. The voltammetric peak for the oxidation of pyrogallol in a pH 7 buffer solution at the modified electrode occurred at 0.13 V, much lower than the bare SPCE and preanodized SPCE. The experimental parameters, including electropolymerization conditions, solution pH values and applied potentials were optimized to improve the voltammetric responses. A linear calibration plot, based on flow‐injection amperometry, was obtained for 1–1000 µM pyrogallol, and a slope of 0.030 µA/µM was obtained. The detection limit (S/N=3) was 0.63 µM.     

Label‐Free Amperometric Detection of Albumin with an Oil/Water‐type Flow Cell for Urine Protein Analysis

The 1,2‐dichloroethane (DCE)/water interface, with an anionic surfactant, dinonylnaphthalenesulfonate (DNNS^?), being present in DCE, was utilized for label‐free detection of albumin. An oil/water‐type flow cell was prepared using a porous PTFE tube and dipping the tube in the DCE solution containing DNNS^?. This flow cell provided a well‐defined current response linear to the albumin concentration up to 10 µM with a detection limit of 1.2 µM. The current response is due to the interfacial adsorption of albumin molecules depending on the Galvani potential difference. Possible interference from creatinine in the urine could be avoided by a conventional dialysis treatment.     

Fast Amperometric Determination of Enzymatic Activity of Glutaminase

ABSTRACT

The activity of the enzyme glutaminase has been measured using a glutamate electrochemical biosensor based on H₂O₂ detection. Calibration curves for glutamate detection and for glutaminase activity using standard glutaminase from Escherichia coli demonstrated the high sensitivity and the rapid analysis time of this novel amperometric procedure, which was 100 times more sensitive than that reported in liternature.

Porcine liver and kidney tissue and human kidney tissue samples have been tested for glutaminase activity, demonstrating the possibility to perform measurement directly on whole tissues, with no need of sample extraction and purification.     

Determination of lisinopril using anion exchange chromatography with integrated pulsed amperometric detection

A rapid and practical method for direct detection of lisinopril in anion exchange chromatography(AEC) has been developed with integrated pulsed amperometric detection(IPAD).Dionex AS 18(250 mm×2 mm) and AG 18(50 mm×2 mm) columns and 40 mmol/L NaOH solution were used for separation.Multi-step potential waveform parameters were optimized to maximize the signal-to-noise ratio(S/N).Utilizing the optimized waveform,the repeatability(intra-day) precision and intermediate(inter-day) precision were obtained with relative standard deviation(RSD) of 0.74,0.93,respectively.The limit of quantification(LOQ) and limit of detection(LOD) were found to be 0.37,0.12ng/mL,respectively,with the correlation coefficient of 0.9998 over concentration range 0.01-1μg/mL.The present method was successfully applied to the determination of lisinopril in human plasma.The recoveries of plasma sample spiked by 0.2μg/mL,0.8μg/mL lisinopril were 98.31-103.23%with RSD of 1.41%, 0.61%,respectively.     

Opioid Peptides Determination by Tyrosinase-Modified Oxygen Electrode

Abstract

Opioid peptides morphiceptin (Tyr-Pro-Phe-Pro-NH₂), [D-Ala², D-Leu⁵]-enkephalin (Tyr-D-Ala-Gly-Phe-D-Leu, DADLE) and [D-Thr²]-Leu-enkephalin-Thr (Tyr-D-Thr-Gly-Phe-Leu-Thr, DTLET) containing tyrosine has been studied in the reaction with mushroom tyrosinase immobilized on Clark-type oxygen electrode. A 4–6-times higher response is observed for tyrosine compared to peptides. The detection limit of the tyrosinase-modified electrode for DADLE, morphiceptin and DTLET was 6 μM, 9 μM and 16 μM, respectively.     

Direct Titration of Nitrate with Diphenylthallium(III) Sulfate

Abstract

Nitrate may be titrated with diphenylthallium(III) sulfate. The titration may be monitored amperometrically or potentiometrically. Fluoride, perchlorate, sulfate and phosphate do not interfere. Chloride, bromide and iodide interfere and must be removed. For amperometric titration, the range is 5 – 22 × 10^?3 M nitrate.