A multi-purpose tubular flow-through sensor was constructed with an AgI-based membrane. The membrane was prepared by pressing silver salts (AgI, Ag_2S) and powdered Teflon. This membrane was incorporated in the tubular flow-through sensor body. A 2-mm diameter hole was drilled through the center of the tubular sensor and the membrane, thus determining the active sensor volume of about 4 microL. The tubular sensor with reference electrode was placed into a complex flow-injection sy! stem and used for the flow-through determination of N-acetyl-L-cysteine, (NAC), in perchloric acid medium, pH=1. Linear dependence was established between the recorded signal height and the concentration of NAC in the injected sample. The recorded change in potential for a decade change in concentration, 62 mV {;p(NAC)};^-1, in the concentration range from 1×10^-4 to 1×10^-1 M, was based on the formation mechanism of the sparingly soluble deposit between silver and NAC on the surface of the sensitive part of the membrane.

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