Chromatographic Separation and Photometric Analysis of the Components of Nile Blue Sulphate

Abstract

Samples of Nile blue sulphate (Geigy and G. T. Gurr) were separated by silicic acid thin layer chromatography. The blue sulphated oxazine base was found to consist of 3 components with identical absorption spectra in the visible range. These probably represent isomeric forms of the dye. The red oxazone travelled as a single component. At least 6 minor constituents, present in small amount, were identified. Spectrophotometric examination showed that the sulphated oxazine base has 3 absorption maxima. The absorption spectrum is influenced by pH, dye concentration, dye solvent, and physical state. The absorption spectra of the oxazone and free oxazine base were also measured. These showed marked solvatochromic effects, absorption maxima moving to shorter wavelengths with decreasing solvent polarity.