Optimization of the extraction of azo colorants used in toy products.

Azo dyes are widely used in formulations intended for children use. But their potential toxicity raised the need of an efficient and fast method of analysis. A study for the optimization of the extraction of some azo colorants used in toys was conducted. Several extraction methods for the selected analytes were evaluated and compared, i.e., supercritical fluid extraction (SFE), microwave-assisted extraction (MAE) and Soxhlet extraction. Poly(vinyl chloride) samples spiked with known quantities of the studied dyes were prepared. The influence of critical variables on analyte recoveries in SFE and MAE was investigated by using a full-level factorial design, where most significant parameters as well as order interactions were studied in each case. The analytes were subsequently detected by high-performance liquid chromatography with UV detection. The three extraction techniques were compared in terms of reproducibility, selectivity and analyte recoveries. MAE showed higher recoveries (above 98%), except for the diazo dye (nearly 60%). Reproducibilities were generally good for the three methods (relative standard deviation lower than 2.0%).

Optimization of parameters for the analysis of aromatic amines in finger-paints.

A study for the optimisation of the supercritical fluid extraction (SFE) of some aromatic amines (4-chloro-o-toluidine, 2-naphthylamine, 4-aminobiphenyl and benzidine) in finger-paints was conducted. The influence of different variables related to the technique on recoveries was investigated. The analytes were subsequently analysed by gas chromatography after SFE. The study allowed the estimation of four main factors (temperature, pressure, static time and volume of modifier) on recoveries by the use of a two-level factor design, where most significant parameters as well as second- and third-order interactions were identified. Other factors, such as type and volume of modifier and time of contact between the spiker solution and the sample prior to extraction, were also studied. The influence of matrix on extraction recovery was also evaluated by applying the method to different finger-paints, and recoveries were similar or even higher in some cases. The drying process of samples was also studied, while classical drying in an oven and microwaves were compared, with similar efficiencies in both methods. The method was validated by extracting the aromatic amines from some commercial finger-paints.

Determination of some aromatic amines in finger-paints for children's use by supercritical fluid extraction combined with gas chromatography.

A test method based on supercritical fluid extraction (SFE) and gas chromatography has been developed for some aromatic amines, such as 4-chloro-o-toluidine, beta-naphthylamine and 4-aminobiphenyl. A two-level factor design was used as the optimization procedure. Four main variables were considered: CO2 pressure, extraction temperature, static extraction time and volume of modifier (methanol). Results obtained for 4-chloro-o-toluidine, indicated that the volume of modifier was the variable with the most important influence on extraction, CO2 pressure had a negative effect and temperature and time were less significant. For the other amines, static time was the most important variable in both cases, followed by CO2 pressure and volume of modifier, with no influence of temperature. SFE was compared with Soxhlet extraction, and was found to give higher recoveries in all cases. Other commercial finger-paints were tested for the presence of aromatic amines.