3,4-dihydroxyphenylacetic acid (DOPAC) is a normal constituent of rat brain tissue. A mass fragmentographic method for determination of DOPAC in rat brain tissue has been described. It is major metabolite of dopamine (DA). The voltammetric reduction of DOPAC has been studied at a glassy carbon electrode modified with single-wall carbon nanotubes (SWNTs). Semi-automatic fluorometric assay technique for DOPAC has been reported.