Electrochemical Detection and Quantification of Lithium Ions in Authentic Human Saliva Using LiMnO-Modified Electrodes.

We report an electrochemical sensor for the detection of lithium ions (Li) in authentic human saliva at lithium manganese oxide (LiMnO)-modified glassy carbon electrodes (LMO-GCEs) and screen-printed electrodes (LMO-SPEs). The sensing strategy is based on an initial galvanostatic delithiation of LMO followed by linear stripping voltammetry (LSV) to detect the reinsertion of Li in the analyte. The process was investigated using powder X-ray diffraction and voltammetry. LSV measurements reveal a measurable lower limit of 50.0 μM in both LiClO aqueous solutions and synthetic saliva samples, demonstrating the applicability of the proposed analytical method down to low Li concentrations. Four different samples of authentic human saliva were then analyzed with the established sensing strategy using LMO-SPEs, showing good linearity over a concentration range up to 5.0 mM Li with high reproducibility (RSD < 7%) and applicability for routine monitoring purposes. The total time needed to analyze a sample is less than 3 min.