Polychromasia of cresyl violet dyes; a chemical explanation of variations in pre-World War II products.

Abstract

Darrow red (9-acetylamino-5-aminobenzo[α]phenoxazonium chloride) and its 10-methyl derivative, respective precursors of cresyl violet acetate (5,9-diaminobenzo[α] phenoxazonium acetate) and 5,9-diamino-10-methylbenzo[α]phenoxazomium acetate (the compound which duplicates visible absorbance spectra of the violet component of prewar German cresyl echt violet and the current foreign product cresyl fast violet), yielded polychrome products when subjected to alkaline hydrolyses. The hydrolyses were accomplished by refluxing 17.5 gm of each acetylated compound with 25 gm of NaOH in 250 ml of H2O. At the end of 1.5 hr, visible spectra revealed, in each case, the presence of three components: the starting material, the deacetylated 9-amino compound (a cresyl violet) and the 5-keto derivative. Additional refluxing for 6.5 hr resulted in a product containing only the deacetylated 9-amino compound and the 5-keto derivative in approximately equivalent amounts. The latter mixture was not altered by additional refluxing. Absorbance maxima of compounds resulting from the hydrolysis of the 10-methyl derivative of Darrow red were bathochromic by 4-6 mμ to their counterparts obtained from the hydrolysis of Darrow red. The experiments indicate that minor variations in manufacturing processes can readily affect the properties of these biological stains.