Effect of Ionic Liquid Structure on the Electrochemical Response of Dopamine at Room Temperature Ionic Liquid‐modified Carbon Paste Electrodes (IL–CPE)

Expression and purification of epitope vaccine against four virulence proteins from Helicobacter pylori and construction of label-free electrochemical immunosensor

The epitope vaccine against four virulence proteins (FVpE) from Helicobacter pylori (H. pylori) was expressed and purified. Western blot and Enzyme-linked Immunosorbent Assays (ELISA) were used to identify and investigate the immunoreactivity of FVpE protein. The immune-sensing platform based on titanium carbide/colloidal gold nanoparticles@carbon nanofiber/ionic liquid composites electrode was constructed for immobilizing FVpE. Electrochemical impedance spectroscopy (EIS) was used to study the electrochemical properties of the modified electrodes. The relevant influenced factors were optimized including pH value, antigen concentration, and incubating time. The prepared H. pylori label-free electrochemical immunosensor was used for antibody detection using differential pulse voltammetry (DPV). Under the optimal experimental conditions, the linear ranges of H. pylori antibodies, including anti-H. pylori, cytotoxin-associated gene A (CagA), vacuolating cytotoxin-associated gene A (VacA), and urease A (UreA), were all 0.1-5 ng mL-1, except urease B (UreB, 0.1-4.5 ng mL-1). The selectivity study showed that other antibodies had little influence on the detection of H. pylori antibodies. The immunosensor could be used to detect serum samples, and the recoveries were in the range of 68.5%-100.5%.

Simultaneous Determination of Dopamine and Uric Acid in Real Samples Using a Voltammetric Nanosensor Based on Co-MOF, Graphene Oxide, and 1-Methyl-3-butylimidazolium Bromide

A chemically modified carbon paste electrode, based on a CoMOF-graphene oxide (GO) and an ionic liquid of 1-methyl-3-butylimidazolium bromide (CoMOF-GO/1-M,3-BB/CPE), was fabricated for the simultaneous determination of dopamine (DA) and uric acid (UA). The prepared CoMOF/GO nanocomposite was characterized by field emission-scanning electron microscopy (FE-SEM), the X-ray diffraction (XRD) method, a N₂ adsorption-desorption isotherm, and an energy dispersive spectrometer (EDS). The electrochemical sensor clearly illustrated catalytic activity towards the redox reaction of dopamine (DA), which can be authenticated by comparing the increased oxidation peak current with the bare carbon paste electrode. The CoMOF-GO/1-M,3-BB/CPE exhibits a wide linear response for DA in the concentration range of 0.1 to 300.0 µM, with a detection limit of 0.04 µM. The oxidation peaks' potential for DA and uric acid (UA) were separated well in the mixture containing the two compounds. This study demonstrated a simple and effective method for detecting DA and UA in real samples.

Electroanalytical performance of a β-cyclodextrin and ionic liquid modified carbon paste electrode for the determination of verapamil in urine and pharmaceutical formulation

The analytical performance of sensitive and cost-effective electrochemical sensors based on ionic liquids (ILs) with the bis(trifluoromethylsulfonyl)imide anion, [NTf2]-, and the imidazolium cation with different alkyl chain lengths for electrochemical oxidation of verapamil (VER) was investigated. 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][NTf2]) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2]) were studied as possible materials for modification of a carbon paste electrode (CPE) for trace-level determination of VER. The experimental parameters including selection of the working electrode, the pH of working media, and the amount of CPE modifiers were investigated. Among them, the [EMIM][NTf2]-CPE with 4.3 wt% of IL was selected as the most appropriate for the square wave voltammetric (SWV) determination of VER at pH 5.0. Cyclic voltammetric studies showed that the electrochemical oxidation of VER was adsorption controlled. Consequently, the square wave adsorptive stripping voltammetric (SW-AdSV) parameters were optimized with Eacc = -0.4 V and tacc = 180 s as the most suitable for accumulation of VER on the electrode surface. The electroanalytical performance of the [EMIM][NTf2]-CPE was further improved by its in situ electrochemical modification with β-cyclodextrin (β-CD) and the linear concentration range of VER was from 0.006 to 0.129 μg mL-1; the relative standard deviation did not exceed 0.7%, and the evaluated limit of detection in model solution was 0.002 μg mL-1. The β-CD/[EMIM][NTf2]-CPE showed adequate selectivity towards VER in the presence of inorganic ions and interferents usually found in human urine. The proposed sensor was successfully applied for VER determination in a spiked human urine sample and pharmaceutical formulation with good repeatability and recovery.

Application of Ionic Liquids in Electrochemistry-Recent Advances

In this review, the roles of room temperature ionic liquids (RTILs) and RTIL based solvent systems as proposed alternatives for conventional organic electrolyte solutions are described. Ionic liquids are introduced as well as the relevant properties for their use in electrochemistry (reduction of ohmic losses), such as diffusive molecular motion and ionic conductivity. We have restricted ourselves to provide a survey on the latest, most representative developments and progress made in the use of ionic liquids as electrolytes, in particular achieved by the cyclic voltammetry technique. Thus, the present review comprises literature from 2015 onward covering the different aspects of RTILs, from the knowledge of these media to the use of their properties for electrochemical processes. Out of the scope of this review are heat transfer applications, medical or biological applications, and multiphasic reactions.