Deuterium Tracer for Accurate Online Lube-Oil-Consumption Measurement: Stability, Compatibility and Tribological Characteristics

Because of the impact of lubrication on the efficiency and the lifecycle cost and emissions, the lubricating-oil consumption (LOC) is one of the key indicators in the research and development of internal combustion engines. State-of-the-art methods for LOC measurement are based on the use of a certain tracer to track the oil consumption. However, all of the currently available tracers have their downsides (e.g., the use of a radioactive tracer, corrosive emissions, etc.). Therefore, in the course of this research project, a new tracer substance that is based on a stable nonradioactive isotope of hydrogen—deuterium—was developed and tested thoroughly. The LOC is monitored by a hydrogen/deuterium isotopic ration in the exhaust gas by using an isotopic water analyzer. Tribologically important properties, such as the viscosity, stability, and compatibility of the tracer were investigated by laboratory experiments by using several tools, such as infrared spectroscopy, gas chromatography, thermogravimetry, etc. The properties relevant to the applicability of the method, such as the accuracy and the reproducibility, were investigated by engine test-bench experiments. Finally, long-term stability tests of the tracer were conducted with a field test.

Kinetic isotope effects and synthetic strategies for deuterated carbon-11 and fluorine-18 labelled PET radiopharmaceuticals

The deuterium labelling of pharmaceuticals is a useful strategy for altering pharmacokinetic properties, particularly for improving metabolic resistance. The pharmacological effects of such metabolites are often assumed to be negligible during standard drug discovery and are factored in later at the clinical phases of development, where the risks and benefits of the treatment and side-effects can be wholly assessed. This paradigm does not translate to the discovery of radiopharmaceuticals, however, as the confounding effects of radiometabolites can inevitably show in preliminary positron emission tomography (PET) scans and thus complicate interpretation. Consequently, the formation of radiometabolites is crucial to take into consideration, compared to non-radioactive metabolites, and the application of deuterium labelling is a particularly attractive approach to minimise radiometabolite formation. Herein, we provide a comprehensive overview of the deuterated carbon-11 and fluorine-18 radiopharmaceuticals employed in PET imaging experiments. Specifically, we explore six categories of deuterated radiopharmaceuticals used to investigate the activities of monoamine oxygenase (MAO), choline, translocator protein (TSPO), vesicular monoamine transporter 2 (VMAT2), neurotransmission and the diagnosis of Alzheimer's disease; from which we derive four prominent deuteration strategies giving rise to a kinetic isotope effect (KIE) for reducing the rate of metabolism. Synthetic approaches for over thirty of these deuterated radiopharmaceuticals are discussed from the perspective of deuterium and radioisotope incorporation, alongside an evaluation of the deuterium labelling and radiolabelling efficacies across these independent studies. Clinical and manufacturing implications are also discussed to provide a more comprehensive overview of how deuterated radiopharmaceuticals may be introduced to routine practice.

Small-angle neutron scattering measurements of mixtures of hydrogenous and deuterated n-tetradecane

Small-angle neutron scattering (SANS) measurements on mixtures of hydrogenous and deuterated species can be used to determine the distribution of molecules in these blends. The molecules are isotopically distinguishable but are chemically identical. This approach has been applied with great success to polymer science, but fewer examples are available for small molecules, such as solvents. SANS measurements of combinations of the linear alkane n-tetradecane were performed on mixtures prepared at different volume fractions of hydrogenous and deuterated alkane. These data have been analyzed using the framework of polymer scattering, and good agreement between experiment and theory was found.