Combination pH electrodes of special design: Temperature characteristics and performance in poorly-buffered waters.

The performance of 5 combination pH electrodes with special design features has been assessed. Two electrodes were intended for measurements in low-conductivity waters, two were designed to have a rapid and stable temperature response and one electrode shared both features. The performance in low-conductivity waters was either poor or merely acceptable; better results have been obtained with separate glass and reference electrodes. The electrodes designed to have good temperature response were better in this respect than conventional combination electrodes, but the same or better performance can be obtained by use of separate glass and remote-junction reference electrodes. It should be noted that the temperature coefficients of these combination electrodes were the same as for almost all pH electrodes: any improvement was only in the rate and stability of response.