Voltammetric determination of nifedipine at a hanging mercury drop electrode and a mercury meniscus modified silver amalgam electrode

The voltammetric behavior of nifedipine (NFD) has been studied with two different types of working electrodes (hanging mercury drop mini-electrode (HMDmE) and mercury meniscus silver solid amalgam electrode (m-AgSAE)) using differential pulse voltammetry (DPV). The optimal conditions for DPV determination are: a mixture of Britton-Robinson (BR) buffer pH 8 with methanol in three different ratios (1:1, 9:1, 99:1), respectively, in the concentration range of 0.2 to 20 µmol/L. The limit of quantification (LQ) was found to be 0.12 µmol/L (HMDmE) and 1.2 µmol/L (m-AgSAE). Attempts to increase the sensitivity using adsorptive stripping DPV at both HMDmE and m-AgSAE were not successful. Using the optimum conditions, the practical application of the newly developed method has been verified on the determination of NFD in spiked samples of drinking and river water

Preparation and Investigation of Silver Nanoparticle–Antibody Bioconjugates for Electrochemical Immunoassay of Tick-Borne Encephalitis

A new simple electrochemical immunosensor approach for the determination of antibodies to tick-borne encephalitis virus (TBEV) in immunological products was developed and tested. The assay is performed by detecting the silver reduction signal in the bioconjugates with antibodies (Ab@AgNP). Here, signal is read by cathodic linear sweep voltammetry (CLSV) through the detection of silver chloride reduction on a gold–carbon composite electrode (GCCE). Covalent immobilization of the antigen on the electrode surface was performed after thiolation and glutarization of the GCCE. Specific attention has been paid to the selection of conditions for stabilizing both the silver nanoparticles and their Ab@AgNP. A simple flocculation test with NaCl was used to select the concentration of antibodies, and the additional stabilizer bovine serum albumin (BSA) was used for Ab@AgNP preparation. The antibodies to TBEV were quantified in the range from 50 IU·mL?1 to 1600 IU·mL?1, with a detection limit of 50 IU·mL?1. The coefficient of determination (r2) is 0.989. The electrochemical immunosensor was successfully applied to check the quality of immunological products containing IgG antibodies to TBEV. The present work paves the path for a novel method for monitoring TBEV in biological fluids

Label-Free Electrochemical Biosensors for the Determination of Flaviviruses: Dengue, Zika, and Japanese Encephalitis

A highly effective way to improve prognosis of viral infectious diseases and to determine the outcome of infection is early, fast, simple, and efficient diagnosis of viral pathogens in biological fluids. Among a wide range of viral pathogens, Flaviviruses attract a special attention. Flavivirus genus includes more than 70 viruses, the most familiar being dengue virus (DENV), Zika virus (ZIKV), and Japanese encephalitis virus (JEV). Haemorrhagic and encephalitis diseases are the most common severe consequences of flaviviral infection. Currently, increasing attention is being paid to the development of electrochemical immunological methods for the determination of Flaviviruses. This review critically compares and evaluates recent research progress in electrochemical biosensing of DENV, ZIKV, and JEV without labelling. Specific attention is paid to comparison of detection strategies, electrode materials, and analytical characteristics. The potential of so far developed biosensors is discussed together with an outlook for further development in this field

A Laser Reduced Graphene Oxide Grid Electrode for the Voltammetric Determination of Carbaryl

Laser-reduced graphene oxide (LRGO) on a polyethylene terephthalate (PET) substrate was prepared in one step to obtain the LRGO grid electrode for sensitive carbaryl determination. The grid form results in a grid distribution of different electrochemically active zones affecting the electroactive substance diffusion towards the electrode surface and increasing the electrochemical sensitivity for carbaryl determination. Carbaryl is electrochemically irreversibly oxidized at the secondary amine moiety of the molecule with the loss of one proton and one electron in the pH range from 5 to 7 by linear scan voltammetry (LSV) on the LRGO grid electrode with a scan rate of 300 mV/s. Some interference of the juice matrix molecules does not significantly affect the LSV oxidation current of carbaryl on the LRGO grid electrode after adsorptive accumulation without applied potential. The LRGO grid electrode can be used for LSV determination of carbaryl in fruit juices in the concentration range from 0.25 to 128 mg/L with LOD of 0.1 mg/L. The fabrication of the LRGO grid electrode opens up possibilities for further inexpensive monitoring of carbaryl in other fruit juices and fruits

PORTUGALIAE ELECTROCHIMICA ACTA Possibilities and Limitations of Mercury and Mercury-based Electrodes in Practical Electroanalysis of Biologically Active Organic Compounds

Abstract Personal opinion of the author on the use of mercury and amalgam electrodes for determination of trace amounts of biologically active organic compounds is expressed. This view is supported by references to numerous reviews and original papers from UNESCO Laboratory of environmental electrochemistry supporting the claim that both mercury and amalgam electrodes can play useful role in modern practically oriented analytical laboratories

Silver Solid Amalgam Electrodes as Sensors for Chemical Carcinogens

The applicability of differential pulse voltammetry (DPV) and adsorptivestripping voltammetry (AdSV) at a non-toxic meniscus-modified silver solid amalgamelectrode (m-AgSAE) for the determination of trace amounts of genotoxic substances wasdemonstrated on the determination of micromolar and submicromolar concentrations of3-nitrofluoranthene using methanol - 0.01 mol L-1 NaOH (9:1) mixture as a base electrolyteand of Ostazine Orange using 0.01 mol L-1 NaOH as a base electrolyte

Silver Solid Amalgam Electrodes as Sensors for Chemical Carcinogens

The applicability of differential pulse voltammetry (DPV) and adsorptivestripping voltammetry (AdSV) at a non-toxic meniscus-modified silver solid amalgamelectrode (m-AgSAE) for the determination of trace amounts of genotoxic substances wasdemonstrated on the determination of micromolar and submicromolar concentrations of3-nitrofluoranthene using methanol - 0.01 mol L-1 NaOH (9:1) mixture as a base electrolyteand of Ostazine Orange using 0.01 mol L-1 NaOH as a base electrolyte

Determination of Chloramphenicol by Differential Pulse Voltammetry at Carbon Paste Electrodes - the Use of Sodium Sulfite for Removal of Oxygen from Electrode Surface

The possibility of determination of chloramphenicol by differential pulse voltammetry at four different carbon paste electrodes, in the full pH range (2-12) of Britton-Robinson (BR) buffer was investigated. Electrodes were prepared by mixing spectroscopic graphite powder or glassy carbon microbeads with mineral oil (Nujol) or tricresyl phosphate. Under optimal conditions (BR buffer pH 12, the electrode prepared from glassy carbon microbeads and tricresyl phosphate), linear calibration graph was obtained only in 10-5 M chloramphenicol concentration range. Determination of lower concentrations of chloramphenicol was complicated by irreproducible peak of oxygen from the carbon paste which overlapped with peak of chloramphenicol. Addition of sodium sulfite removed the oxygen peak without influence on the peak of chloramphenicol. Under optimal conditions (electrode paste made from glassy carbon microbeads, BR buffer pH 10 and 0.5 M sodium sulfite), straight calibration line was obtained in the 10(-6) and 10(-5) M chloramphenicol concentration range. Limit of determination was 5 x 10(-7) mol/l

The polarographic and voltammetric determination of 2,6-dichloro-4-nitro-2'-acetylamino-4'-diethylaminoazobenzene

The polarographic reduction of the title azo dye has been studied, a mechanism has been proposed and optimal conditions have been found for its analytical use. The detection limit using a classical dropping mercury electrode was 2 . 10^-7 mol l^-1 for TAST polarography and 1 . 10^-8 mol l^-1 for differential pulse polarography. Using a hanging mercury drop electrode, the detection limit was 9 . 10^-9 mol l^-1 for fast scan differential pulse voltammetry and 1 . 10^-8 mol l^-1 for linear scan voltammetry. Adsorption accumulation of the test substance on the surface of the hanging mercury drop electrode led to a further decrease in the detection limit to 1 . 10^-9 mol l^-1 for fast scan differential pulse voltammetry and 7 . 10^-10 mol l^-1 for linear scan voltammetry