Metachromasy. III. Metachromatic Behavior of Trypaflavine in the Presence of Polyphosphates with Various Chain Lengths

The interaction of trypaflavine with sodium polyphosphate in aqueous solutions in the pH range 6–7 has been investigated by means of light absorption spectroscopy, conductometric titration and ultrafiltration. The metachromatic behavior of the bound dye was characterized in terms of hypso- and hypochromic effects in both visible and UV regions where no pronounced metachromasy band was observed. The effects were studied by varying the mixing ratio of polymer residue to dye, P/D, from 0.1 to 10000. They were found to be maximum in the P/D range 2–10. The effect of the chain length of polyphosphate on metachromasy was determined by use of fourteen refractionated samples with the degree of polymerization, , ranging from 8 to 158. No metachromasy appeared in samples with <7. It fully developed for those with >20, sharply depending on the chain length between 7 and 20. By conductometric titration and ultrafiltration, it was verified that the dye binds to the ionized phosphate almost at 1 : 1, and that the disappearance of metachromasy with the increase in P/D values or with the addition of salts results from two entirely different processes. The results were compared with the data for other dyes.