Novel applications of online pH determinations at temperatures from -35 ^°C to 130 ^°C in technical and biological media, which are all but ideal aqueous solutions, require new approaches to pH monitoring. The glass electrode, introduced nearly hundred years ago, and chemical sensors based on field effect transistors (ISFET) show specific drawbacks with respect to handling and long-time stability. Proton sensitive metal oxides seem to be a promising and alternative to the state-of-the-art measuring methods, and might overcome some problems of classical hydrogen electrodes and reference electrodes.

Against the background of environmental compatibility and unrestricted technical usability, synthetic, and natural transformer oils are critically compared in long‐term tests under high voltage using electrical and instrumental analytical methods. Synthetic alkyl esters of pentaerythrol appear to be sustainable and sometimes superior substitutes for mineral oils in terms of chemical stability, viscosity, permittivity, and heat transport. Natural esters of unsaturated fatty acids are found to be unsuitable for equipment exposed to moist air. Adsorbed water appears to be a general problem in transformer oils. The aging mechanisms and molecular changes during long‐term operation include radical reactions, and the formation, isomerization and cleavage of CC bonds. Extensive material data are provided.

Frequency-dependent capacitance C(ω) is a rapid and reliable method for the determination of the state-of-charge (SoC) of electrochemical storage devices. The state-of-the-art of SoC monitoring using impedance spectroscopy is reviewed, and complemented by original 1.5-year long-term electrical impedance measurements of several commercially available supercapacitors. It is found that the kinetics of the self-discharge of supercapacitors comprises at least two characteristic time constants in the range of days and months. The curvature of the Nyquist curve at frequencies above 10 Hz (charge transfer resistance) depends on the available electric charge as well, but it is of little use for applications. Lithium-ion batteries demonstrate a linear correlation between voltage and capacitance as long as overcharge and deep discharge are avoided.

State-of-charge (SOC) and state-of-health (SOH) of different cell chemistries were investigated using long-time cycle tests. This practical guide illustrates how differential capacity dQ/dU (capacitance) obtained from discharge curves, impedance spectra, and cyclic voltammograms can be used for the instant diagnosis of lithium-ion batteries without fully charging and discharging the cell. The increase of dU/dQ is an early indicator of upcoming heat events and deep discharge. The criterion dQ/dU = dU/dQ = 1 could serve as an indicator for “full charge”. The frequency response of capacitance correlates with the available charge of the battery and reflects overcharge events and deep discharges long before the battery fails. It is not necessary to measure down to extremely low frequencies because the charge transfer pseudocapacitance of around 10 Hz reflects well the SOC. Computer-aided calculation methods for the evaluation of measurements in industrial environments and for the training of students are presented.

By cyclic voltammetry at high scan rates, the electrochemical properties of RuO₂ in acidic and alkaline solutions were investigated in detail. Thirteen current peaks can be distinguished in sulfuric acid and sodium hydroxide. With respect to the pH sensitivity of RuO₂ electrodes, we considered charge calculations, peak currents, and apparent diffusion coefficients. The nature of the Ru(II) oxidation was clarified by Ru(I)−Ru(III) species.

Compared to the medical, economic and social implications of COVID-19 vaccinations, little attention has been paid to the ecological balance to date. This study is an attempt to estimate the environmental impact of two mRNA vaccines in terms of CO₂ equivalents with respect to their different freezing strategies and supply chain organization. Although it is impossible to accurately calculate the actual environmental impact of the new biochemical synthesis technology, it becomes apparent that transport accounts for up to 99% of the total carbon footprint. The emissions for air freight, road transportation and last-mile delivery are nearly as 19 times the emissions generated from ultra-deep freeze technologies, the production of dry ice, glass and medical polymers for packaging. The carbon footprint of a single mRNA vaccine dose injected into a patient is about 0.01 to 0.2 kg CO₂ equivalents, depending on the cooling technology and the logistic routes to the vaccination sites in Germany.