Validation of an analytical procedure for the determination of oxidative hair dyes in cosmetic formulations.
A high range and variety of cosmetic formulations that contain oxidative hair dyes and matrix-forming compounds have been industrially developed over recent years and are now available on the international market. Member states of the European Union are responsible for conducting analyses of cosmetic products as deemed necessary by law and European regulation enforcement. Therefore, inspection authorities as well as the cosmetics trade and industry need validated analytical methods for the identification, characterization, and/or quality control of specific active ingredients or formulations with the aim of implementing the European Union Cosmetic Directives (76/768/ECC, 95/17/EC). In this frame, we validated a candidate reference method that enables the identification and quantification of hair dye-forming compounds. This method consists of a separation by RP-HPLC coupled with a DAD after a liquid-liquid extraction procedure for separating matrix components from the dye-forming compounds. The validation of the method includes common criteria such as the repeatability of the analysis and the establishment of figures of merit, as well as statistical evaluations and quality assurance in order to follow the recommendations of the Eurachem guide for analytical measurements.
HPLC Candidate Reference Method for Oxidative Hair Dye Analysis. I. Separation and Stability Testing.
Abstract Among the different methods of changing the color of human hair, oxidative hair dyeing plays an important role. The formulations consist of a broad spectrum of organic compounds among which most of the dye forming substances, i. e. the dye intermediates, are of aromatic nature. With the aim of establishing an analytical method for the separation and quantification of the dye intermediates, the chromatographic behavior of a selection of these products was investigated. The separation was done by HPLC, using reversed-phase chromatography. UV and diode array detection were employed. A quantitative separation procedure was established with which it is possible to separate and identify intermediates according to their retention times and their UV spectra. In order to test the influence of light, temperature, and antioxidants on the sample solutions, changes in the chromatographic behavior of the investigated substances were recorded as a function of these parameters. It was shown that their influence ...
Determination of dye intermediates in oxidative hair dyes by fused-silica capillary gas chromatography.
A fused-silica capillary gas chromatographic method is described for the determination of dye intermediates in oxidative hair dyes. An appropriate amount of hair dye sample is dissolved in 10 ml of methanol containing 0.25 g of ammonium thioglycolate and an appropriate amount of 2-amino-4-methylphenol as an internal standard. This solution is directly injected into a gas chromatograph. A fused-silica capillary column with cross-linked methyl silicone OV-1 or SE-54 as a liquid phase yields excellent resolution of dye intermediates. Some factors affecting the quantitation of dye intermediates are discussed. The proposed method gave good recoveries and reproducibilities, and permits simultaneous determination of various types of dye intermediates without any pretreatment. The use of a nitrogen-phosphorus detector allows the selective detection of nitrogen-containing dye intermediates. This simple and versatile method is applicable for the determination of dye intermediates in commercial hair dyes.