A tool for direct determination of surface Bronsted acidities of solids, in terms of concentration and strength, was proposed and applied to carbon materials, based on the quantitative H/D exchange kinetics between DO and the acid solid, i.e. the -O-H acid surface groups in the case of carbons. Calibration was performed using well-characterized zeolites with known acidities, and allowed the concentration of surface Bronsted acidity sites in mu mol/g to be derived from the integrated surfaces of the H/D exchange curve. This was done y the direct measurement of the OHD signal via mass spectrometry. The strength of the acidity was directly linked to the rate constant of the H/D exchange kinetic. This easy of use direct method is highly flexible and covers the whole acidity scale from weakly acidic to strongly acidic materials. (c) 2005 Elsevier B.V. All rights reserved.