Inline NMR Detection of Li$^+$ in Aqueous Solutions Using a Cryogen-Free Magnet at 4.7 T

Lithium is of major importance for many areas of technology, especially batteries, and is therefore relevant to both the industrial and private sectors. High-performance, ideally inline-compatible analytics are important for economical and environmentally friendly lithium extraction. Nuclear Magnetic Resonance is an established analytical method that has already been used in numerous inline applications. For this study on $^7$Li NMR in flow, a cryogen-free magnet with a variable magnetic field was used, whereby a field strength of 4.7 T was set for the measurements for compatibility reasons. The influences of flow velocity, repetition time, and lithium concentration were investigated in spin echo measurements. This allows for defining limitations and potential fields of application for the measurement setup. In addition, the possibilities of internal pre-polarization were investigated. The results show that the method and setup are well suited for inline flow measurements on $^7$Li and have great potential for expanding the range of applications