Photodynamic sensitizers assay: rapid and sensitive iodometric measurement.

A rapid, sensitive and simple spectrophotometric method for the detection of 1O2 produced by photodynamic photosensitizers in slightly acid and air-saturated aqueous solutions has been developed. The method is based on the reaction of 1O2 (produced by photodynamic processes) with I- in the presence of ammonium molybdate as a catalyst. The reaction product I3-, proportional to 1O2, is followed spectrophotometrically at 355 nm. Several ways of avoiding interference with other oxidizing compounds, either present before or produced during the irradiation, are described.