A polarographic study of Evans blue and its combination with plasma proteins.

The binding of T-1824 (Evans blue) with plasma has been extensively studied in the past by Allen and Orahovats (1) by means of the cellophane sorption method. Although this approach yielded excellent results, a simpler and more direct method seemed desirable. The basis for this new method is furnished by the observation, made in 1939,’ that the free T-1824 gives rise to a distinct polarographic reduction wave, whereas the proteinbound dye is completely inactive polarographically. (The combination of another azo dye, methyl orange, is different in some respects (2) and will be discussed later.)