Determination of Banned Azo Dyes in Leather

Dyes are commercially indispensable and the expanding industry offers a complete palette of colors. Azo dyes constitute the largest chemical class of synthetic dyes because of their versatility, low price, and ease of production. These dyes may, however, pose health risk to humans due to formation of mutagenic/carcinogenic aromatic amines upon reductive cleavage of their azo groups (-N=N-). Therefore, the EU has introduced a ban on the marketing and use of certain azo dyes in textile and leather goods. The appended papers present analytical procedures for determination of banned azo dyes in leather. The main foci in the development of these procedures was enhancement of sample preparation by employing diverse instrumentation-based techniques, including supercritical-fluid extraction (SFE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), and stir-bar sorptive extraction (SBSE). Despite extensive optimization, inaccurate results were obtained when quantification was performed by means of common external standard calibration. Standard additions of the corresponding azo dyes turned out to be a feasible way to tackle the problem with systematic errors. However, the usefulness of the developed standard addition methodology relies on knowledge of, and access to, the azo dyes present in the leather. Nevertheless, all developed procedures proved superior, in terms of accuracy, to the prevailing German standard (i.e. DIN 53316) regardless of quantification method employed

An ultrasound-assisted extraction procedure for the determination of banned azo dyes in leather

The potential risk for consumers to be exposed to banned azo dyes in leather is strong motivation for the development of an analytical test procedure with improved accuracy. The currently most accepted analytical procedure for this application, the German standard DIN 53316 method, suffers from major drawbacks including low accuracy and the usage of hazardous organic solvents. As a consequence, an alternative procedure based on ultrasound-assisted extraction (UAE) was developed for the determination of banned azo dyes in leather. The optimized UAE procedure was applied to bovine, sheep, and goat leather. These results were compared with those obtained by employing the DIN 53316 method or microwave-assisted extraction (MAE). Usually, the performance of UAE was better than the DIN 53316 method and comparable to MAE. Furthermore, the UAE procedure utilizes acidified water as extraction solvent rather than methyl tert.-butyl ether. Because of its simplicity and the inexpensive equipment required, the proposed procedure has the potential to become the preferred alternative for analyzing banned azo dyes in leather on a routine basis

Standard addition - A way of improving quantification of banned azo dyes in leather

An analytical procedure based on supercritical-fluid extraction and microwave-assisted extraction was applied on six different real leather samples for the determination of banned azo dyes. Determination of the dyes was performed indirectly by measuring their corresponding harmful aromatic amines, formed after reduction. A comparative study between external standard calibration and standard addition using both the dyes as well as the corresponding amines showed that the latter quantification method provided the highest accuracy

Optimization of an analytical procedure for the determination of banned azo dyes in leather

The possibility of improving an existing method, based on supercritical-fluid extraction (SFE) and microwave-assisted extraction (MAE), for the determination of banned azo dyes in leather has been studied. Thus, optimization of experimental conditions in different steps (degreasing, reduction, and extraction) of the analytical procedure was performed. The influence of different variables (reaction time, temperature, and concentration of reducing agent) on the reduction process was evaluated by use of a factorial design. It was found that the concentration of the reducing agent and the interaction between time and temperature were the most influential variables. Consequently, by applying a higher temperature, the reaction time could be halved. The use of acidified water as extraction solvent in MAE was also investigated. Usually 1 mol L-1 HCl was superior to methanol and buffer in terms of extraction efficiency. In conclusion, the present method gave significantly higher recoveries in comparison with the original method. All dyes were determined indirectly by measuring their corresponding harmful amines, formed after reduction by use of sodium dithionite

Application of standard addition methodology for the determination of banned azo dyes in different leather types

An analytical procedure based on microwave-assisted extraction (MAE) and standard addition was applied for the determination of banned azo dyes in bovine, sheep, and goat leather. Standard addition at four different concentration levels was performed using azo dyes, dissolved either in methanol or water. All dyes were determined indirectly by measuring their corresponding harmful aromatic amines, formed after reduction by use of sodium dithionite. Comparing found amounts of amines with theoretical target values allowed an assessment of accuracy. The recoveries were also compared with those obtained for non-spiked samples using external standard calibration. The standard addition approaches provided much better accuracy than external standard calibration, with recoveries close to 100% for most amines. Since there was no great difference in recoveries when using methanol or water as solvent, preparation of the dyes in methanol might be preferred because of the faster evaporation of the solvent after spiking. (c) 2005 Elsevier B.V. All rights reserved

Determination of banned azo dyes in consumer goods

Azo dyes, extensively used for coloring a variety of consumer goods, such as leather, clothes, food, and toys, can under certain conditions be reduced to form confirmed or suspected carcinogenic aromatic amines. This article gives an overview of the state of development of analytical procedures for the determination of such azo dyes, which are banned by the European Commission. (C) 2004 Elsevier Ltd. All rights reserved

Alkaline hydrolysis combined with stir-bar sorptive extraction or sonication for the determination of banned azo dyes in leather

Two approaches based on alkaline hydrolysis, in combination with either stir-bar sorptive extraction (SBSE) or sonication, were developed for the determination of banned azo dyes in bovine leather. All dyes were determined indirectly by measuring their corresponding harmful amines, formed after chemical reduction. Quantification was performed by employing standard addition methodology to compensate for analyte losses due to sample preparation (e.g. incomplete extraction). The mean recoveries (n=3) obtained by employing the SBSE and sonication procedures were 100 percent (RSD=26 percent) and 114 percent (RSD=11 percent), respectively. The linearity of the standard addition curves obtained was reasonable [SBSE (mean R-2=0.980) and sonication (mean R-2=0.997)]. Both procedures were very simple to perform and provided clean LC-UV chromatograms. Taking into account the repeatability, sonication was considered the preferred alternative

Detection of banned amines in leather

There currently exists legislation within Europe banning the use of dyestuffs based on certain carcinogenic amine compounds. Currently a test method exists that is used by the industry (CEN ISO TS 17234 based on DIN 53316). This is able to detect twenty of the compounds listed by the legislation but is not validated for the recently added 2-methoxyaniline and is unsuitable for analysis of -Aminoazobenzene. The method is also known to have problems related to the reproducibility of the analysis both within and between laboratories. Work has been carried out as part of a European Commission funded project to look into the issues surrounding the test method. Within the project there are three key objectives. These are: * To carry out a feasibility study for the development of a certified reference material for banned azo dyes in leather * To develop a method suitable for certifying any proposed reference material * To develop a method suitable for routine testing in industry. Research to develop a method for certifying the reference material has resulted in a procedure based on supercritical fluid extraction for degreasing the leather, followed by sodium dithionite microwave assisted extraction in order to reduce the dyestuffs present. The samples obtained are then cleaned up using solid phase extraction before analysis using High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD). The technique of standard addition is also used to improve recovery rates. In order to certify a reference material it is necessary to have a method which is very accurate and precise. The method is not planned for general use and, therefore, has incorporated techniques that may not be suitable for all laboratories. A routine test method has also been developed. This method was designed considering that it should be suitable for use in laboratories within the leather industry on a routine basis. It should be relatively straight forward to carry out, providing results with good reproducibility. It is not critical, however, to obtain 100% recovery rates, provided the results are consistent. Also of importance is the cost effectiveness of the method along with the speed in which results can be obtained. A method has been developed incorporating ultrasound based degreasing that can be carried out on the day of analysis. This is followed by an optimised sodium dithionite reduction and solid phase extraction for clean-up. Both HPLC-DAD and Gas Chromatography with Mass Spectroscopy (GCMS) have been evaluated for analysis. During development the methods have been assessed in inter-laboratory trials