Three analytical methods of oxidative dyes in hair dyes have been developed by High Performance Liquid Chromatography (HPLC).
The first method, paired ion chromatography, employs octadecylsilica (TSK GEL LS-410, 5μ) as column, and as eluent, methanol (25v/v%) and the solution (75v/v%) prepared by dissolving 0.01M sodium octanesulfonate (counter ion) to 0.025M phosphate buffer adjusted to pH 2.5 with 5% phosphoric acid. The second method employs the same column as 1st method and as eluent, methanol and 0.1M phosphate buffer (pH 5.0) (10:90v/v%).
The third method employs as column μ-Bondapak CN (10μ) coated cyanopropylsilane, and as eluent ethanol and pentane (30:70v/v%).
The methods are not only accurate and convenient, almost no clean-up, but provides remarkable determination of p-phenylenediamine, o-, m-, and p-aminophenol and so forth, and the average recovery rate exceeds 95% (coefficient of variance; 2.6% maximun). The application of the techniques to hair dye products on the market showed good qualitative results with detecting almost no obstacle substance.
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