The development of a flow-injection system for pH determination using a pH ion-sensitive field-effect transistor in conjuction with a tubular flor-through nitrate ion-selective electrode (ISE) as a reference electrode is described. With this system, the linear working range extends from pH 1 to 13 with a sensitivity of 56 mV per pH unit and a relative standard deviation of 0.4%. A stable baseline and good respose are obtained by placing the tubular ISE in a closed branch of the main channel. © 1992.
- Flow system
- Ion-selective electrodes
- Ion-sensitive field -effect transistors