Simultaneous determination of captopril, acetaminophen and tryptophan at a modified electrode based on carbon nanotubes

► An electrochemical sensor was prepared by carbon paste electrode modified with a synthesized compound and carbon nanotubes. ► Its electrochemical behavior was investigated by cyclic voltammetry. ► Electro-oxidation of captopril at this sensor was occurred at a potential about 500 mV less than unmodified electrode. ► The sensor was used successfully for simultaneous determination of captopril, acetaminophen and tryptophan.