This work reports on the excited singlet-state absorption cross-section spectra of both biprotonated and nonprotonated states of meso-tetrakis(p-sulphonatophenyl) porphyrin obtained by means of the Z-scan technique with white-light continuum pulses. Although our main purpose was to determine these photo-physical parameters in a wide spectral range, we also analyzed the role of accumulative effects arising as consequence of the pulse chirp caused by the group velocity dispersion. This effect leads to apparent changes in the measured excited-state absorption spectra, which can be corrected during the fitting procedure to yield meaningful absorption cross-section values. (C) 2008 Elsevier B. V. All rights reserved.