On-line direct potentiometry of residual water in organic solvents using the proton isoconcentration technique

Abstract

A laboratory prototype monitor, based on direct potentiometry, has been designed and constructed for the determination of residual water in organic solvents using the proton isoconcentration technique (PICT). In the monitor, a sample stream is bled off and mixed with a buffer before passing through a cell containing a pH glass electrode, a reference electrode and an automatic temperature compensation probe. The instrument is calibrated with standard solutions containing water in the same solvent, the useful (i.e., sensitive) water range being 0–10%m/m water. The system is controlled by a program running on a general purpose minicomputer. Results obtained for residual water in methanol, ethanol, propan-1-ol, propan-2-ol, ethane-1,2-diol, propanone and butan-2-one show PICT to be sensitive, accurate and reproducible with an average response time of 7–10 min.