A new, highly sensitive Adsorptive Stripping Voltammetric method for levodopa determination was developed. As a working electrode, the glassy carbon electrode (GCE) modified with carbon black (CB), RuO₂·xH₂O (RuO₂) and Nafion was used (CB-RuO₂-Nafion GCE). Levodopa signal obtained on the modified electrode was 12 times higher compared to GCE. During research, instrumental parameters were optimized: sampling time t_s = 10 ms, waiting time t_w = 10 ms, step potential E_s = 5 mV and pulse amplitude ΔE = 50 mV. Preconcentration potential E_prec was equal to 0 mV. The best results were obtained in 0.025 M perchloric acid (approx. pH 1.4). Signal repeatability measured on the CB-RuO₂-Nafion modified electrode for 0.2 µM of levodopa was equal to 2.1% (levodopa concentration 1 µM, n = 5). Linearity of the method was achieved in the concentration range from 1 to 8 µM. Limit of detection was equal to 17 nM. Recoveries calculated for pharmaceutical products and tap water measurements were in the range 102–105%, which confirms the accuracy of the developed. The applicability of the method was confirmed by analysis of pharmaceutical products and tap water samples. Based on obtained results, it might be concluded that the developed voltammetric method could be a useful tool in routine drug analysis.

A new electrochemical sensor based on hierarchical carbon nanofibers with Ni and Co nanoparticles (eCNF/CNT/NiCo-GCE) was developed. The presented sensor may be characterized by high sensitivity, good electrical conductivity, and electrocatalytic properties. Reproducibility of its preparation expressed as %RSD (relative standard deviation) was equal to 9.7% (n = 5). The repeatability of the signal register on eCNF/CNT/NiCo-GCE was equal to 3.4% (n = 9). The developed sensor was applied in the determination of the antihistamine drug—cetirizine hydrochloride (CTZ). Measurement conditions, such as DPV (differential pulse voltammetry) parameters, supporting electrolyte composition and concentration were optimized. CTZ exhibits a linear response in three concentration ranges: 0.05–6 µM (r = 0.988); 7–32 (r = 0.992); and 42–112 (r = 0.999). Based on the calibration performed, the limit of detection (LOD) and limit of quantification (LOQ) were calculated and were equal to 14 nM and 42 nM, respectively. The applicability of the optimized method for the determination of CTZ was proven by analysis of its concentration in real samples, such as pharmaceutical products and body fluids (urine and plasma). The results were satisfactory and the calculated recoveries (97–115%) suggest that the method may be considered accurate. The obtained results proved that the developed sensor and optimized method may be used in routine laboratory practice.

A new voltametric method for highly sensitive propranolol (PROP) determination was developed. A glassy carbon electrode modified with a hybrid material made of carbon black (CB) and Nafion was used as the working electrode. The preconcentration potential and time were optimized (550 mV and 15 s), as well as the supporting electrolyte (0.1 mol L⁻¹ H₂SO₄). For 15 s preconcentration time, linearity was achieved in the range 0.5–3.5 μmol L⁻¹ and for 120 s in 0.02–0.14 μmol L⁻¹. Based on the conducted calibration (120 s preconcentration time) limit of detection (LOD) was calculated and was equal to 7 nmol L⁻¹. To verify the usefulness of the developed method, propranolol determination was carried out in real samples (tablets and freeze-dried urine). Recoveries were calculated and were in the range 92–102%, suggesting that the method might be considered as accurate. The repeatability of the signal expressed as relative standard deviation (RSD) was equal to 1.5% (n = 9, PROP concentration 2.5 µmol L⁻¹). The obtained results proved that the developed method for propranolol determination might be successfully applied in routine laboratory practice.

This article presents the current state of knowledge regarding electrochemical methods for determining the active substances within drugs that are used in the treatment of type 1 and type 2 diabetes. Electrochemical methods of analysis, due to their sensitivity and easiness, are a great alternative to other, usually more expensive analytical assays. The determination of active substances mentioned in this review is based on oxidation or reduction processes on the surface of the working electrode. A wide variety of working electrodes, often modified with materials such as nanoparticles or conducting polymers, have been used for the highly sensitive analysis of antidiabetic drugs. The presented assays allow us to determine the compounds of interest in various samples, such as pharmaceutical products or different human bodily fluids.

High purity quartz glass is an important material in high-tech industries like semiconductors and photovoltaics due to, among other properties, its good mechanical performance at high temperatures. Small amounts of Al in silica glass (in the range between 20 ppm and 100 ppm) have previously been shown to increase the viscosity of the SiO₂ glass. The underlying mechanism for this increase is, however, not well understood. In this paper we report on the local structural and electronic effects of the presence of Al in the SiO₂ structure by density functional theory (DFT). Comparing the quartz and cristobalite polymorphs, we found that the driving force for Al substitution is larger in the denser quartz structure compared to cristobalite, and that oxygen vacancy (Vo) formation is most stabilized in the nearest neighbour position relative to Al in both polymorphs. Al was not found to inherently strengthen the SiO₂ network in the two crystalline polymorphs considered. However, our results suggest that Al preferentially substitutes Si in denser ring configurations, which combined with local Vo formation could lead to locally favourable SiO₂ network reconstructions in SiO₂ glasses (likely towards 6-membered rings), which could propagate causing an increase in the viscosity. Furthermore, we show that the presence of Al can lower the stability of OH groups due to increased electrostatic interactions between the substitutional Al and H₂O which may also be a contributing factor in the increased viscosity of Al doped SiO₂ glass. The modelling results are in line with the experimental fluorescence and FT-IR spectroscopy data confirming that the presence of Al in the glass causes formation of oxygen vacancies and correlates with a lower fictive temperature which typically corresponds to a larger average Si–O–Si angle in the glass structure. Our results suggest that Al's contribution to high glass viscosity is not solely due to the substitution of Si atoms by Al atoms in the glass structure but rather due to structural changes of the silica network the substitution causes.

Aceclofenac (ACL) is an anti-inflammatory drug, which is taken by patients who mainly suffer from rheumatoid conditions. In this work, we propose a new voltammetric method that allows the determination of ACL in pharmaceutics, urine, and plasma. As a working electrode, a glassy carbon electrode (GCE) modified with carbon nanofibers, carbon nanotubes, and NiCo nanoparticles (eCNF/CNT/NiCo-GCE) was used. The mentioned sensors are characterized by good repeatability and sensitivity, and their process of preparation is simple, fast, and cost-effective. Instrumental and method parameters were optimized, and the influence of interferences was investigated. To validate the analytical performance of the method, calibration was conducted. Good linearity was obtained (0.05–1.4 µM, r = 0.998), as well as excellent limit of detection (LOD) and limit of quantification (LOQ) values (0.7 nM and 2.1 nM, respectively). Calculated recoveries that were in the range of 98%–105% indicate that this method is accurate and might be used in routine laboratory practice.