A simple and fast flow injection amperometry for the determination of methimazole in pharmaceutical preparations using an unmodified boron-doped diamond electrode

In this work, an automated flow injection analysis (FIA) connected to a boron-doped diamond electrode (BDDE) was originally developed for the analysis of methimazole in pharmaceutical preparations. At a modification-free BDDE, methimazole was easilly oxidized. For the analysis of the mechanisms occurring at the electrode surface, cyclic voltammetry was employed to evaluate the impact of fundamental experimental parameters, such as pH and scan rate, on the BDDE response. For the quantitative detection, the FIA amperometric approach was constructed and used as a fast and sensitive method. The suggested approach provided a broad linear range of 0.5–50 µmol/L and a low detection limit of 10 nmol/L (signal-to-noise ratio = 3). Furthermore, the BDDE was successfully utilized to quantify methimazole in genuine samples from a variety of medicines, and its performance remained steady after more than 50 tests. The findings of amperometric measurements exhibit excellent repeatability, with relative standard deviations of less than 3.9 and 4.7 % for intra-day and inter-day, respectively. The findings indicated that, compared with traditional approaches, the suggested method has the following advantages: quick analysis time, simplicity, highly sensitive output, and no need for complicated operational processes

Glucose and Glutamate Detection by Oxidase/Hemin Peroxidase Mimic Cascades Assembled on Macro‐ and Microelectrodes

Abstract Enzymatic cascades are routinely used for electroanalysis of redox inactive species that can be enzymatically converted into species electroactive at moderate potentials, such as H2O2 produced by FAD‐dependent oxidases oxidising their substrates by O2. However, such cascades adaptation to micro‐biosensors is limited by enhanced mass‐transfer of produced H2O2 into solution, not to the sensing layer. Here, bi‐enzyme sensors for glucose or glutamate, produced by cross‐linking peroxidase and oxidases on carbon‐nanotube‐modified graphite macro‐electrodes (Gr), showed the from 0.1 to 10 mM glucose/glutamate linear response, while bio‐modified 5 μm carbon fibre electrodes (CFE) were mute due to fast transfer of enzymatically produced H2O2 into solution. By replacing peroxidase with peroxidase‐mimicking hemin in polyethyleneimine, the sensitivity of detection at Gr improved 3‐fold, enabling 2.8 μM glucose and 4.5 μM glutamate limits of detection, but not at CFE. Fast mass‐transfer of H2O2 from CFE to solution was restricted by the Nafion membrane facilitating glucose detection at CFE with a sensitivity of 1.67 A cm−2 M−1, at −0.6 V, escaping interference from other brain‐fluid components, redox‐inactive at this potential. Such membrane‐restricted cascade system provides the analytical access to a large group of enzymes that can be integrated in multiple enzymatic cascades for biosensing at microelectrodes