The behavior of the fluorescence signal produced during oxidation
of indigotrisulfonate by ozone was investigated. In a first experiment,
a set of filters impregnated with indigo were allowed to react with
ozone, and the solutions obtained after extraction of the filters with
water were evaluated. An intense fluorescence signal was observed,
with excitation and emission maxima at 245 nm and 400 nm,
respectively. In a second experiment, three sets of filters impregnated
with ITS reagent were exposed to different amounts of ozone. One
was allowed to react with ozone until partial filter decoloration was
achieved, and another until there was total loss of color. The
fluorescence spectra of the resultant solutions were compared with
those obtained for the third set of filters that had not been exposed to
ozone (Fig. 3). The results showed that the ITS solution itself did not
fluoresce, but that the product of reaction did, with the maximum
fluorescence signal at 400 nm being proportional to the amount of
ozone that had reacted with the ITS.