Abstract: A simple flow cell for potentiometric detection is described. It was assembled by making use of two perspex pieces fixed together by four screws, and allow the connection of plane membrane conventional electrodes to flow system. Details about its construction are presented. The device performance was evaluated by making use of a cyanide ion-selective electrode. The relative standard deviation was ~0.5% with a detection limit of 8.0 x 10^-6 mol CN- L-1. Under experimental conditions, the linear range was 10^-5 to 10^-2 mol L-1.

Abstract: This study presents a flow injection system for the sequential determination of free (CN-) and total (CN-+ HCN) cyanide using a potentiometric method which employs two different processes for the determination of these two chemical species. The first process is based on direct detection of CN-using an ion-selective electrode for cyanide. In the second process, the sample is mixed with acid, and the released HCN is transferred across a PTFE membrane. The flow system employs three solenoid valves, a gas diffusion chamber, an ion-selective electrode, a potentiometer, and a computer with an AID conversion card. A Turbo Pascal(R) computer program automatically performs all the steps involved in data acquisition and processing. The standard deviation far the results obtained with the proposed method was 0.5%.