Kinetic, static and stirring errors of liquid junction reference electrodes

Abstract

Response characteristics of reference electrodes were determined by subjecting them to large changes in ionic strength and transference. Commercial electrodes often gave surprisingly poor performance, exhibiting slow, inaccurate and stirring-dependent responses. Slow response is caused primarily by diffusional entrapment of previously measured solutions within the junction. Large offsets at pH extremes or at low ionic strength are caused by storage of no-flow electrodes in standard buffers, junction charge and improper junction geometry. Stirring potentials are caused by shifts in offset error with local changes in concentration at the junction surface. Adequate outward flow or diffusion of junction electrolyte serves to suppress these anomalies. Reference problems are often undetectable in the standard pH buffers typically used for calibration.