Oil is a prominent, but multifaceted material class with a wide variety of applications. Technical oils, crude oils as well as edibles are main subclasses. In this review, the question is addressed how low-field NMR can contribute in oil characterization as an analytical tool, mainly with respect to quality control. Prerequisite in the development of a quality control application, however, is a detailed understanding of the oils and of the measurement. Low-field NMR is known as a rich methodical toolbox that was and is explored and further developed to address questions about oils, their quality, and usability as raw materials, during production and formulation as well as in use.

No abstract

Time domain, also named lowfield nuclear magnetic resonance is used to monitor oil degradation by measuring relaxation and diffusion. As quality control of oils is indispensable to optimize oil change intervals while simultaneously preventing machinery damage, the technique was applied to detect the degradation state of engine oils as time domain nuclear magnetic resonance is known as a well suited tool to measure quality control parameters for example in food industry. Correlations with commonly applied oil analytics like viscosity measurements and inductively coupled plasma optical emission spec trometry allow to interpret relaxation and diffusion data in detail and finally to deepen the understanding of oil aging processes. Additionally, the measurement temperature was varied to achieve the maximum sensitivity towards oil aging. Low field NMR is not only realized in form of table top instruments, but also in form of field cycling and single sided NMR devices. Fast field cycling as well as single sided NMR were also explored to study oil aging and to provide valuable insight. The latter device was used to obtain information about translational diffusion and transverse relaxation of oils simultaneously.

Aging of motor oil is characterized by diverse NMR methods to get insight into the chemical processes which occur during aging. Already one-dimensional 1H and 13C spectra reveal the relevance of chemical aging also with respect to the mechanical behavior of oils. As NMR is a quantitative analytical method, the absolute chemical changes can be observed and quantified. In addition, the spectral interpretation in terms of chemical composition is confirmed and deepened by two-dimensional 1H–1H, 1H–13C, and 1H–15N correlation spectra, as well as diffusion and relaxation experiments. The different NMR results are discussed and interpreted to obtain a thorough picture about aging processes of motor oils.

No abstract