POTENTIOMETRIC FLOW-INJECTION DETERMINATION OF CYSTEINE IN THE PRESENCE OF CYSTINE USING A TUBULAR ELECTRODE WITH AG(I)-BASED MEMBRANE AS DETECTOR

A solid-state AgI-based electrode was constructed as a compact tubular sensor; the sensing hole had an id of 2.0 mm and a length of 1.2 mm. An example of the application of the tubular electrode is given in for m of the determination of cysteine (RSH) in 0.1 M HClO4 as supporting electrolyte using a flow-injection system. A rectilinear calibration g raph is obtained by plotting the peak height versus concentration of R SH in the RSH concentration range from 1 x 10(-4) to 1 x 10(-1) mol L( -1). The experimental slope 61 mV {P(RSH)}(-1) is obtained, in good ag reement with the theoretical value. Essentially, no interference was c aused by cystine.