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.
Optimization and validation of an analytical procedure for the determination of oxidative hair dyes in commercial cosmetic formulations.
A method has been developed and validated for the analysis of commonly used intermediates of oxidative hair dyes in commercial cosmetic formulations, including both liquid and cream forms, in dark and blonde shades. The commercial formulations are submitted to extraction by an organic solvent, and the resulting aqueous phase is analyzed by reverse-phase HPLC with a gradient elution and detection with DAD and/or ESI-MS-MS. A spectra library containing 200-400 nm spectra of the target substances and their HPLC retention times has been recorded for the identification. The quantification of the target substances is also performed after spiking of the commercial formulations, using an external calibration. The recoveries obtained are very good for all selected intermediates. The whole procedure has been found to be highly suitable for the identification and quantification of dye intermediates. Also implemented has been a database containing (a) the retention times, (b) the spectral, MS, and MS/MS characteristics of the intermediates, (c) acidity constant values of some intermediates of interest experimentally determined and compared to the available NIST values, (d) the chromatographic conditions used, (e) the behavior towards extraction of dye intermediates, and (f) matrix compounds.
Gas-liquid chromatographic determination of toxic diamines in permanent hair dyes.
A rapid, simple and sensitive analytical method has been developed for the simultaneous determination of 1,4-diaminobenzene, 2,5-diaminotoluene and 2,4-diaminoanisole in permanent (oxidation type) hair dyes. The method utilizes an ethyl acetate extraction in the presence of NaCl followed by direct injection into a gas liquid chromatograph equipped with a flame-ionization detector. The detection limits are 5 ng/microliter each for 1,4-diaminobenzene and 2,5-diaminotoluene and 20 ng/microliter for 2,4-diaminoanisole. The relative standard deviations at 5 tims the detection limits are 5.6, 5.8 and 4.6% for these three compounds, respectively. Recovery of diamines from "spiked" dyes was generally found to be greater than 85%.