The invention disclosed is a total organic carbon (TOC) analyzer comprised of an electrochemical cell comprising a diamond-film electrode (2) doped with boron or other conductivity including material. The diamond-film electrode is the working electrode and carries out the oxidation of TOC to produce carbon dioxide. The apparatus further comprises sensors for detecting the carbon dioxide produced. Such sensors include but are not limited to a tunable diode laser (1) and/or ion-selective electrode (5). The invention also discloses a method for measuring TOC in an aqueous solution using a total organic carbon analyzer.