We present in this paper the surface derivatization of polyanhydrides with triethylamine for labeling the hydroxyl group. The reaction was verified with diffuse reflectance FTIR spectroscopy. Surface derivatization of poly(fumaric-co-sebacic)anhydride of 50:50 and 20:80 compositions was performed and ESCA measurements showed the surface nitrogen concentration in good agreement with stoichiometry values.