Simple quantification of surface carboxylic acids on chemically oxidized multi-walled carbon nanotubes

► Simple and rapid quantification of acidic groups on oxidized MWCNT surfaces has been proposed. ► The quantification was performed using pH measurements and pre-determined pKa value. ► The results were consistent with those obtained from XPS and titration. ► Variations in acid concentrations as a function of the type of oxidants and oxidation time were also investigated.