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.
Simultaneous determination of 13 components in oxidative hair dyes by high-performance chromatography using an ion-pair reagent.
A reliable high-performance liquid chromatography (HPLC) method was developed for the simultaneous determination of 13 dye intermediates, including benzenediamines, aminophenols, benzenediols, naphthalenediol, and diaminopyridine, in oxidative hair dyes. Samples were extracted with 50% ethanol by adding sodium dithionite to prevent oxidation. The influences of buffer type, buffer pH, ion-pair reagent, and elution gradient were studied. A C18 column with aqueous compatibility and acetonitrile-citric acid mobile phase system (pH 2.6) with sodium 1-octanesulfonate as ion-pair reagent were selected for the separation of target compounds. Detection was performed by a diode array detector, (DAD) and two different wavelengths (280 and 331 nm) were used for quantification. Results showed that 13 dye intermediates got good separation within 25 min. The detection limits of these compounds were in the range of 0.2-2 mg/l. The calibration curves were linear within 2-500 mg/l with 0.999 as a typical correlation coefficient. The recoveries of target compounds in hair dyes ranged from 81.7% to 102.0% with four addition levels. The method described was validated by five different laboratories and successfully applied to the analysis of commercial oxidative hair dyes.
In-services and empty threats: The roles of organizational practices and workplace experiences in shaping U.S. educators' understandings of students' rights.
This paper applies theoretical frameworks from organizational sociology and sociolegal studies to examine factors associated with educators' conceptions of students' rights to due process in disciplinary actions. We analyze a unique representative data set of 402 teachers and 200 administrators in U.S. high schools to investigate how educators understand the rights to due process articulated in the Supreme Court case of Goss v. Lopez (1975). We then examine whether individual characteristics and participation in organizational processes are associated with educators' understandings of students' due process rights. Findings suggest that educators' understandings of students' entitlements to due process vary with educators' level of education, experience of school-related legal threats, and participation in district or diocese in-service training programs on students' rights. Results point to organizational climate as a key factor in shaping educators' rights conceptions and the role of law in American schools.