Search

The authors of this article applied the determination of phenolic and flavonoid content in small berries to create a didactic cycle based on student-centered active learning (SCAL) in which students actively participated in the topic while studying and profile-forming as future biology and chemistry teachers. The fundamental part of the proposed didactic cycle is that students solve the following task: Determine the phenolic and flavonoid content in berries (Vaccinium myrtillus L., Vaccinium vitis-idaea L., and Vaccinium corymbosum L.) in your region. The submitted interdisciplinary topic is relevant to everyday life, and it aroused interest and enthusiasm among students. The students had the opportunity to test their theoretical knowledge in practical experimental research, and they attempted to work as researchers.

Bare boron-doped diamond electrode (BDDE) was applied for investigation of deposition/stripping processes of silver ions in various supporting electrolytes. The highest signal was observed in 0.1 mol dm−3 HNO3. Detection of silver ions is also possible in 0.1 mol dm−3 Na2S2O3 where Ag+ is strongly complexed as [Ag(S2O3)2]3−. Though the sensitivity is 100 times lower, the potential of anodic dissolution of silver is significantly shifted towards the negative values. This shift might be useful for solving of some interferences which may occur in the detection process. After preliminary cyclic voltammetry, the analytical performance was studied by differential pulse anodic stripping voltammetry (DPASV) and square-wave anodic stripping voltammetry. Deposition potential of − 0.18 V vs. Ag/AgCl and deposition time of 240 s were selected as optimum DPASV parameters. The lowest detection limit of 2.0 × 10–10 mol dm−3 was achieved with DPASV in HNO3. Negligible effect of possible interferents on Ag response proved to be a good selectivity of method. The proposed method after validation was also applied to real samples analysis of some commercial products with complex matrix. The obtained results are statistically identical with data declared by manufacturer and gained by independent technique, making this method suitable for commercial product control.

This short review deals with the properties and significance of the determination of selenium, which is in trace amounts an essential element for animals and humans, but toxic at high concentrations. It may cause oxidative stress in cells, which leads to the chronic disease called selenosis. Several analytical techniques have been developed for its detection, but electroanalytical methods are advantageous due to simple sample preparation, speed of analysis and high sensitivity of measurements, especially in the case of stripping voltammetry very low detection limits even in picomoles per liter can be reached. A variety of working electrodes based on mercury, carbon, silver, platinum and gold materials were applied to the analysis of selenium in various samples. Only selenium in oxidation state + IV is electroactive therefore the most of voltammetric determinations are devoted to it. However, it is possible to detect also other forms of selenium by indirect electrochemistry approach.

Voltammetric behavior of omeprazole on chemically unmodified boron-doped diamond electrode was investigated. Omeprazole is possible to oxidize and reduce in various supporting electrolytes. Both processes are strongly dependent on pH value of the solution. Well defined oxidation and reduction signal of omeprazole was observed at high and low pH values of supporting electrolyte. Kinetics of charge transfer in the pH range from 3 to 10 in various supporting electrolytes was studied and characterized by the estimation of formal potentials (+1.07 to +0.89 V for oxidation and −0.95 to −1.18 V for omeprazole reduction), charge transfer coefficients (0.52–0.33 for oxidation and 0.19–0.17 for reduction) together with standard heterogeneous rate constants. The analytical performance was studied with linear sweep voltammetry, square-wave voltammetry and differential pulse voltammetry. The lowest detection limit of 9.1 × 10 −8 mol L −1 for oxidation of omeprazole was achieved by SWV technique. The proposed simple, sensitive and cheap method was validated and applied for pharmaceutical formulations and human urine as real samples.

Simple and fast electroanalytical method for the detection of tin(II) in bronze has been developed. It is based on synergistic combination of boron-doped diamond electrode as sensitive voltammetric sensor and reaction electrochemistry. The voltammetric response is enhanced by chemical recycling of iodide after electrogeneration of iodine followed by reaction with Sn(II). The charge transfer for the oxidation of iodide to iodine on boron-doped diamond electrode was investigated and characterized in eight different electrolytes. Charge transfer coefficient (0.58 in 0.1 mol L − 1 H 3 PO 4 –0.35 in 0.1 mol L − 1 HCl), formal potential (0.65 V in 0.1 mol L − 1 HClO 4 –0.90 V in 0.1 mol L − 1 NaHCO 3 ) and standard heterogeneous rate constant (4.6 × 10 − 3 cm s − 1 for H 3 PO 4 –2.2 × 10 − 3 cm s − 1 for NaHCO 3 ) were estimated. Based on these values it was observed that the charge transfer is irreversible, but the response is suitable for the quantification of tin(II) in bronze for tire cords. The detection limit of 2.3 × 10 − 7 mol L − 1 was achieved by linear sweep voltammetry. This value is comparable with some expensive and time consuming techniques routinely used for this type of determination.

Very simple and sensitive electroanalytical technique based on synergistic combination of reaction electrochemistry (specificity) and bare boron-doped diamond electrode (sensitivity) for the detection of fluorides in drinking water was developed as variant based on dynamic electrochemistry to ISE analysis. It is based on the formation of electroinactive fluoride complexes with Fe(III) and Ce(IV) ions decreasing such diffusion current of free metal on boron-doped diamond electrode. Due to low background signal of boron-doped diamond electrode reasonably low detection limits of the order of 10 −6 mol L −1 for linear sweep voltammetric method using formation of [FeF 6 ] 3− and 10 −7 mol L −1 in a square-wave variant of this technique have been achieved. This is approximately 1–2 orders lower than in the case of platinum comb-shaped interdigitated microelectrode array. Linear sweep voltammetric method based on [CeF 6 ] 2− complex formation has lower sensitivity and may be suitable for samples with higher content of fluoride and not to analysis of drinking water.

Very simple and fast electroanalytical method for the detection Sb(III) on chemically unmodified boron-doped diamond electrode (BDDE) has been developed. Voltammetric behavior of antimony was investigated in various acidic supporting electrolytes and the most suitable medium for the determination of Sb(III) on bare BDDE has been 6 mol L−1 HClO4 solution. The analytical performance was studied with differential pulse anodic stripping voltammetry (DPASV) with optimized conditions (deposition potential −1 V vs. Ag/ AgCl and deposition time 240 s). An analysis of possible effects due to the presence of other metal ions (especially As(III)) in the solution was eliminated using NaH2PO4 as supporting electrolyte with addition EDTA as selective complexing agent for Sb(III). Speciation of antimony was also investigated. The detection limit of this analytical strategy achieved value of 1.08 × 10−7 mol L−1. The proposed method was validated and applied for natural water from former antimony mines as real samples.