Controlled-growth Mercury Drop Electrode Research Articles

Fast and reliable voltammetric determination of menaquinone (vitamin K2) produced in vitro by Bacillus subtilis cultures

Vitamin K2 (VK2) is one of two natural forms of vitamin K, necessary for the proper functioning of organisms. Currently, it is sourced from chemical synthesis, nonetheless, it is worth reaching out to its natural sources. The aim of the study was to devise a voltammetric procedure for the determination of vitamin K2 (VK2) produced by bacteria in order to find the strain that exhibits the highest efficiency of VK2 production. Bacillus subtilis, isolated from traditional Japanese food (Nattō), was chosen as a model strain. Employment of the Controlled Growth Mercury Drop Electrode (CGMDE) was crucial, as it is the only electrode that allows performing the measurement on the surface specifically renewed directly before, thus minimizing the influence of interferents. This new method was successfully applied for VK2 determination in supernatant samples. Developed procedure is robust and easily adjustable for the variety of biological matrixes. Strong differences in VK2 production depending on cultivation time were observed, but no direct correlation between the VK2 concentration in the breeding medium and the cultivation time was found. The devised protocol will be used in further measurements with different bacteria species that have the ability to produce VK2 and settle in the human intestine.Graphical abstract

Voltammetric determination of thujone in herbal matrices in the presence of Triton X-100

A simple, sensitive and rapid method of low concentration of thujone determination using Controlled Growth Mercury Drop Electrode and Differential Pulse Voltammetry was described. The reduction of thujone in phosphoric acid or potassium nitrate, involves a quasi-reversible and adsorption-controlled two-electron process. In voltammetric experiments the addition of ethanol and Triton X–100 is recommended.Experimental conditions, such as composition of supporting electrolyte, concentration of Triton X-100 and operation parameters were established. The optimal electrolyte should contain: 0.04 mol L−1 phosphoric acid (pH = 1.9) or 0.05 mol L−1 potassium nitrate (pH = 6.4), 0.0002% Triton X-100 and 9.6% ethanol. The calibration graph was linear from 0.7 to 140 mgL−1 of thujone in H3PO4 as supporting electrolyte and from 0.7 to 115 mgL−1 of the analyte in KNO3. The detection limit was 0.4 mgL−1 in H3PO4 and 0.6 mgL−1 in KNO3, with the correlation coefficient of 0.998. The influence of interfering substances, such as Al(III), Bi(III), Cd(II), Cr(III), Cu(II), Pb(II), Tl(I), V(III) and Zn(II) was studied. The proposed method was validated by the thujone recovery study from the specially prepared spiked herbal matrices and alcohol extract. The considered real sample was thuja oil, in which thujone was successfully determined. All measurements were performed without sample preparation.

Voltammetric profiling of absinthes

The paper demonstrates that differential pulse voltammetry with a controlled growth mercury drop electrode, supported by the unsupervised multivariate chemometric methods enables distinguishing of absinthes brands. Signals recorded for the unpretreated samples are repetitive for the same absinthe producer. Unprocessed complex voltammetric signals recorded by different accumulation time were an input data to PCA, HCA and k-means modeling. Homogeneous clusters were formed which reflected the natural order in the set of samples.

NEW MULTIPURPOSE ELECTROCHEMICAL ANALYZER FOR SCIENTIFIC AND ROUTINE TASKS

This work presents a modernized and improved analyzer, different versions of which have been developed by our team over the past 30 years. Modern solutions and fully integrated chips have been applied to this device, which is dedicated to measuring low and very low levels of a recorded value. The up-to-date software fulfills the requirements of scientists, routine analysts, teachers, and students in the areas of electrochemical measurements and the interpretation of recorded signals. The proposed multipurpose analyzer ensures full measuring capability and allows the control of different electrochemical sensors, including the controlled growth mercury drop electrode (CGMDE). Various typical and more advanced signal processing procedures are built-in and are easily accessible.

Development and Validation of an Anodic Stripping Voltammetric Method for Determination of Zn2+ Ions in Brain Microdialysate Samples

An easy, rapid, and sensitive anodic stripping voltammetric method with a controlled growth mercury drop electrode has been developed and validated for the determination of Zn2+ ions in brain microdialysate samples obtained from rats. The considered level of the zinc concentration in the dialysate was 0.5–6 ppb. In the investigated method, the stripping step was carried out by using a differential pulse potential-time voltammetric excitation signal. The optimal experimental conditions as well as the instrumental and accumulation parameters and supporting electrolyte composition were investigated. The optimized method was validated for precision, linearity, and accuracy. Mean recovery 82–110% was achieved, the precision expressed by CV not greater than 7.6% and the linearity given by correlation coefficient not lower than 0.9988. The limit of detection was 0.1 ppb. No interferences were observed. Due to high linearity, precision, and sensitivity, the developed method may be successfully applied in the determination of zinc ions in microdialysate brain samples. The results obtained for the first time demonstrate detailed characteristics of the determination of zinc in the brain microdialysate fluid by the ASV method. It may be applied in a wide range of physiological and pharmacological studies which focus on very low zinc concentration/alteration in various compartments of the organisms.

Influence of the Electrolyte on Triton X-100 Adsorption on Fumed Silica

Fumed silica was used for adsorption of Triton X-100 from electrolyte solutions. Influence of such parameters as the kind of fumed silica and its pretreatment, pH, ionic strength and ionic composition of solution on the process of surfactant adsorption has been studied using differential capacity measurements at a controlled growth mercury drop electrode. The kinetics of Triton adsorption on silica have also been studied. It was found that under optimal conditions 0.1% of fumed silica removes completely 5 ppm of Triton X-100 in time shorter than 1 minute.

Cyclic Voltammetry and Quartz Crystal Microbalance Electrochemical Studies on Thiosalicylic Acid and Dithiodibenzoic Acid

ABSTRACT Cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) were used to study the behavior of thiosalicylic acid (KTS) and dithiodibenzois acid (DTDB) at the controlled-growth mercury drop electrode (CGMDE), at the gold electrode, and at the carbon electrode. The CV method was used to study peak current intensities and peak potentials in relation to pH of the solution, to scan rate and to the concentration of the analyte. Optimum measurement parameters were established and stock solutions developed. The electrode activity was found to be primarily due to the oxidation of the sulhydryl group. The currents observed are diffusion controlled. Electrochemical studies on complexes of KTS with Cu(II) were undertaken at varying constituent proportions and the cathodic peak was found to rise by ca. 70% whereby the sensitivity of the determination was considerably increased. The EQCM method allowed to establish that, as KTS is oxidized, the electrode slightly gains in weight (ca. 80 ng). As DTDB is reduced, the electrode slightly looses in weight (ca 40 ng). Studies on the equimolecular KTS-Cu(II) complex showed the electrode to gain about 125 ng more in weight than in the solutions containing KTS alone, a fact evidencing for the formation of the complex and for its deposition on the electrode surface. A procedure was developed to determine KTS and DTDB in the substance by the CV method. Statistical evaluation of data showed the results to be characterized by good accuracy and precision (RSD 0.80% and 0.61%, respectively).

Increasing the signal to noise ratio in amperometry and polarography using the controlled-growth mercury drop electrode

A new approach to current sampling in amperometric and polarographic measurement is described. This approach requires the application of a step-by-step mode of mercury drop generation. The advantages are: (1) in amperometric measurements an increase of the signal to noise ratio; (2) in polarographic measurements and computer aided experiments the noise level can be markedly reduced.

Stripping analysis on controlled‐growth mercury drop electrode

AbstractIn this study, special consideration is given to the “back‐diffusion effect” accompanying the process of electrochemical preconcentration and during the time between the end of this process and the initiation of stripping (that is, during the rest period). It is shown how far these effects can be eliminated when a Controlled‐Growth Mercury Drop Electrode (CGMDE), is applied. It has been demonstrated that controlled growth of the drop during preelectrolysis allows the formation of a homogeneous amalgamate of the deposited substances in the Hg drop and prevents the occurrence of the back‐diffusion effect. Quantitative relations between these factors and the back‐diffusion into the capillary thread of mercury are presented.

Application of a controlled-growth mercury drop electrode to polarography.

In the proposed device for producing the controlled-growth mercury drop electrode (CGMDE), the mercury outflow is controlled by a fast response valve. Because of this the drop growth mode, rate and size can be modified by the pulse sequence and programmed in advance. The CGMDE retains many features of the DME and SMDE and also has other unique capabilities which are interesting from the point of view of polarography, voltammetry and automatic analysis; recalibration of the drop size may be achieved automatically. The results presented in this paper provide an illustration of these features, particularly those which are of interest in polarography.

Controlled-growth mercury drop electrode.

Controlled-growth mercury drop electrode.