Effects of ultraviolet light on lecithin monolayers in the presence of fluorescein dyes and tetracycline drugs.

A Langmuir trough was employed to measure the effects of u.v. irradiation on the force area characteristics of monolayer films of lecithin spread on aqueous solutions of some dyes and tetracycline drugs both in the absence and presence of Ca2+ and Ni2+. Irradiation caused photochemical reactions which resulted in the expansion of the films and the extent of reaction was measured by the Photosensitive Indices. The reaction with tetracyclines was inhibited by adding Cu2+ or Ni2+ to the substrate. The kinetic orders of the reactions are given.