Analysis of cosmetic dyes V identification of organic synthetic dyes in toilet soaps

The soap is fused in formic acid. Fatty acids are removed with heptane from which later the oil-soluble and some pigment dyes are removed by means of formic acid. The defatted solution of soap in formic acid is diluted and partly neutralized and therefrom the basic, pigment and some acid dyes are isolated with chloroform. Other acid dyes are isolated with help of benzalkonium chloride/chloroform or polyamide. Insoluble dyes are isolated by filtration followed by dissolving in one of the series of solvents. Separation and identification are achieved by means of thin-layer chromatography, absorption spectra and reactions.