INVESTIGATION OF THE RANGE OF A PLASTIC PH SENSOR BASED ON A DIBASIC IONOPHORE

A study is reported of the use of a neutral carrier reagent containing two nitrogen atoms with very different basicities in a pH-sensitive membrane electrode with a view to obtaining a broad response range. This electrode responds well in the pH region of 6-12 but suffers anion interference in the region of pH 2-6. A study is included of the effect of adding various amounts of potassium tetrakis(4-chlorophenyl)borate as an anion suppressing reagent to the membrane in order to reduce the anion interference at low pH values. The conclusion is drawn that an extension to the working pH range is not possible with this approach unless controlled amounts of anion suppressing reagent can be provided to approximately balance the positive charge of the carrier in each region of the pH scale.