Potentiometric titration of thallium(I) with sodium tetraphenylborate, using ion-selective electrodes.

Thallium(I) has been determined by potentiometric titration with sodium tetraphenylborate. The titrations were monitored with a double-junction reference electrode and various liquid-membrane and solid-state ion-selective electrodes. The largest end-point breaks were obtained with the liquid-membrane fluoroborate and nitrate electrodes. The cyanide electrode yielded the largest break of the solid-state electrodes tested. Although the magnitude of the end-point break for the cyanide electrode is considerably less than for the above-mentioned liquid-membrane electrodes, routine use of this electrode is preferred because no conditioning is required for the solid-state electrodes. Precision was satisfactory for all electrodes investigated. Thallium(I) can be titrated with tetraphenylborate at any pH from 1.3 to at least 10.2. Other cations that can be precipitated with tetraphenylborate interfere.