PORPHYRINS AS PROBE MOLECULES IN THE DETECTION OF GASEOUS-POLLUTANTS .1. DIFFUSION OF PYRIDINE IN POLYSTYRENE FILMS CONTAINING ZINC-TETRAPHENYLPORPHYRIN

Zinc-porphyrins can be coordinated by amines, resulting in a red shift in the absorption spectrum. We have taken advantage of this property to study the diffusion of gaseous pyridine in polystyrene films. We ha ve studied the absorption properties of polystyrene films of different thicknesses and calculated the extinction coefficients of Zn-porphyri n in these films. It has been demonstrated that there is no aggregatio n of porphyrins in the film at the concentrations used in this study. We have demonstrated that diffusion of pyridine is dependent on the co ncentration of porphyrin in the film but independent of the film thick ness. A fast response (approximate to 2 min) and a detection limit of 10 mu mol m(-3) of pyridine in atmosphere are obtained. The film can b e regenerated by heating at 383 K under vacuum (1 mmHg). Since the fil ms are found to be sensitive to other amines, a possible application i s the realization of cheap dosimeters for amines.