Spectral absorption and fluorescence of coproporphyrin isomers I and III and the melting-points of their methyl esters

Abstract

The spectral absorption curves of coproporphyrins I and III were found to be identical in the range 300-650 m[mu], and on the acid side of pH 2 show identical changes with varying pH. At acidities below pH 2, the fluorescence efficiencies of these 2 molecules were found quantitatively equivalent. The melting point-composition curve of the tetramethyl esters of coproporphyrins I and III shows that the presence of 10-15% of one isomer may remain undetected in the other, if the m. p, is the sole criterion the resolidification point is the more sensitive index of purity.