Voltammetric Method for Determining the Trace Moisture Content of Organic Solvents Based on Hydrogen-Bonding Interactions with Quinones

Voltammetry experiments were performed on the natural quinone, vitamin K-1 (VK1), in a range of organic solvents of varying dielectric constant that are commonly used for electrochemical measurements [dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetonitrile (MeCN), propionitrile (EtCN), butyronitrile (PrCN), 1,2-dichloroethane (DCE), dichloromethane (DCM), and 1,1,2,2-tetrachloroethane (TCE)]. The water content of the solvents was accurately measured using Karl Fischer (KF) coulometric titrations, and the voltammetric data were used to estimate the degree of hydrogen-bonding interactions between the reduced forms of VK1 and variable levels of water, thereby allowing a ranking of water-substrate interactions in the different solvents. The voltammetric data were analyzed based on interactions that occur between reduced forms of VK1 and the water, the solvent, and the supporting electrolyte. Calibration data were obtained that are independent of the nature of the reference electrode and allow the water content of the solvents to be calculated by performing a single voltammetric scant in the presence of VK1 and 0.2 M supporting electrolyte (Bu4NPF6).