Analysing dangerous substances in liquid or solid form

24 July 2006

An increasingly important issue in the leather industry currently is the ever-growing raft of regulations which lay down just what ingredients are permissible in all manufacturing processes and what level is acceptable in the finished article. Dr Humbert said that today's companies are increasingly aware of the importance of the environment. The leather sector is confronted by the problems of environmental protection and the lawful constraints are increasingly strict and all encompassing. Until the beginning of the nineties, only the basic parameters of wastewater (COD, BOD, pH etc) were followed and controlled. Since then, the situation has developed considerably with requests for monitoring parameters such as PCP (pentachlorophenol), PAH (polycyclic aromatic hydrocarbons) and many other organic micropollutants and the list is steadily increasing. The last stage of this process has been the publication of the European directive (2000/60/CE) [1] which lays down a common policy for wastewater. The behaviour of consumers has also been evolving. Durability was the prevalent argument but the nineties saw requests for greater technical performance. Since then, major medical crises have taken place (eg BSE) and now a real concern for the early 21st century consumer is that a product should be innocuous, not harmful. Products should not contain chemical substances (synthetic or natural), which could have a harmful effect on the health of the consumer. The toxic, mutagenic, carcinogenic products were the first products which led the European Union to publish several Directives prohibiting or limiting the use of these chemical substances (Directive 99/51/CE [2] concerning pentachlorophenol, Directive 2002/61/CE [3] prohibiting the azo dyes etc). During recent years, leather testing laboratories have been required to develop new methods of chemical analysis and acquire the necessary tools to enable them to check the conformity of products compared with the new European directives. The chemistry laboratories of CTC [4] set up new analytical techniques: ICP/OES, ICP/MS, GC/MS, GC/ECD, HPLC/FLUORIMETRY HPLC/DAD etc. Methods were developed to analyse products as varied as: azo dyes, bromodiphenylated ethers, organotin compounds and multi extraction and analysis methods. Nowadays, much European legislation exists concerning leather and other materials used in the leather sector. These texts define the products (shoe, leather etc) the chemical substances and also the conditions of use (produced in contact with the skin etc). Table 1 gives a non exhaustive list of the chemical substances most usually required. Parent water directive Directive 2000/60/CE [1] of the European Parliament and the Council of October 23, 2000, established a framework for a common policy in the field of water, which was transcribed in French law on April 21, 2004. It aims to maintain or restore ecological and chemical quality, thus avoiding a deterioration of surface water and subsoil waters in Europe. The recent adoption of this directive establishes a framework for a common policy in the field and points out the orientations related to the good state of the watery ecosystems. It must be consistent with the objectives of water protection. A list of 'dangerous priority substances' was defined (see Table 2). The ultimate objective of the directive is the improvement of the quality of natural environments by the suppression of these substances. Identification as a dangerous priority substance reflects the intrinsically hazardous properties of a product and indicates that it is 'toxic, persistent and bioaccumulable'. The list drawn up by the European Directive refers to 33 substances (Table 2). In France, the Ministry for Ecology and Durable Development brought the European list up to 87 substances. In fact, a list of 132 substances constituted the reference frame. The MEDD wished to continue monitoring certain substances in the list of the 132 and add it to the list of 33. New extraction techniques In order to be able to cover such a variety of substances as those listed in Table 2, it was first necessary to develop new methods of preparation and extraction. This led CTC to invest in new apparatus such as: * distillation systems (PCP in leathers) * microwave (azo dye analysis, European project : AALARM, micro organic compounds in sludges, fat content in leather) * soxtec/soxhlet (phthalate in pvc, extraction of leather) * head space (COHV, BTEX) * thermodesorption New analytical technique GC/MS Gas chromatography coupled to a mass spectrometer (GC/MS) formed part of the analytical methods used during development. It made it possible to carry out the qualitative proportioning of aromatic amines, the quantitative proportioning of the organotin compounds, bromodiphenylated ether, phthalate and phenol. Mass spectrometry is an extremely significant detection technique which makes it possible to determine molecular structures. HPLC The High Performance Liquid Chromatography (HPLC) facilitates the analysis of very large molecules, of thermolabile or fluorescent compounds. In the study, this technique is used with a detection UV with the diode bar. The objective is to quantify the azo dyes or phenyl urea. This detector makes it possible either to vary the wavelengths or simultaneously, in order to record the absorbance, to cover several wavelengths. Thus, in addition to the recorded signal (chromatogram), this detector makes it possible to provide information which can be used to identify the required compound. Through tackling the various problems along the way, CTC have developed more and more 'expertise' and as a consequence have developed some analytical methods making it possible, for example, to find the cause of problems of odour or discolouration thanks to complex techniques such as fluorimetry, infra red and the head space analyses. Analysis development The challenge for CTC was to develop a powerful method in order to extract and analyse a maximum of compounds at the same time in order to limit the number of analyses and to reduce costs imposed on industrialists. The first step was to classify the various compounds according to their physicochemical properties and find a global analytical solution. Except for semi metals, it led to the determination of two types of family: * the semi volatile and non volatile compounds * volatile compounds Based on the methods already developed, the groups of micropollutants were split within these two large groups. Thereafter, it was necessary to anticipate which compounds could have a similar behaviour by taking into account chemical properties such as thermolability, volatility, stability in acid medium etc. Once the substances were identified, the objective was to determine the types of detection most suited to quantify the compounds while keeping in mind a multi residue logic. For this strategy of analysis (screening) followed by several tests, four groups were essential (Table 3). For certain groups, there are normative references concerning the preparation of the sample (groups IV and II). Nevertheless, for the volatile organic compounds, the optimisation of the analysis was necessary in order to separate the compounds concerned with the Parent Directive for Water. The analysis of organotin compounds had to be carried out several times to refine the quality of the analysis. And with regard to the analysis of the chloroalcanes C10, C13, the lack of reference involved the use of experimental designs in order to find a suitable method of preparation of the sample to discover the right analytical technique to use the second time. The last group of compounds was the one which required the most deliberation although normative references do exist for certain substances. Indeed, the difficulty of the multi residue approach was to find a preparation of the sample which was powerful enough, according to the chemical properties of the compounds (indeed the analysis gathers phenols, triazines, organochlorinated and phosphorated pesticides) and also provide a good quality of analysis. Then, further thought needed to be given on the preparation of the samples. The objective was to find a solvent combination allowing the extraction of the compounds concerned by very diverse chemical properties. The use of experimental designs made it possible, amongst other things, to vary this parameter, but also the pH and the quantity of solvent used according to the load of the matrix. This led to the choice of two different solvents used in acid media, basic and neutral and in quantities depending on the load of the matrix. To conclude, Table 4 gives a summary of the analytical strategy. As a result of this study, CTC now have a range of methods which make it possible to quantify a great number of substances potentially present in effluents. Following the adoption of Directive 2000/60/CE, the Ministry for Ecology and Durable Development (MEDD) set up a study in France involving 5,000 factory sites. The object of this work is to constitute an item zero which will make it possible in the future to better evaluate the evolution of the aquatic environments and their attack on the standards of optimal environmental quality. Obviously the activities of tanneries and megisseries were included in the list of the industrial facilities to be controlled. Thus CTC were brought in to analyse the wastewater of about thirty tanneries and to determine the presence of 87 different substances. * For each type of pollutant (metals, organic volatile compounds, organic non-volatile compounds), CTC determined: * the number of times that one could determine the presence of the substance considered in the effluents. This was then expressed in percentage terms compared with the other tanneries/megisseries tested * For each detected substance, they determined the concentration. Metal analysis The results observed for the analysis of metals (Figure 1) indicated that the three elements most found are chromium, copper and zinc and that, unsurprisingly, chromium is the element which is found in greatest quantity. Organic micro-pollutants On the level of the multi residue analysis concerning the various families of substances (Figure 2), it appears that certain phenols, naphthalene (aromatic hydrocarbon polycyclic) and diethylhexylphthalate (DEHP) are the compounds most found. These substances come primarily from the use of dyes (phenols and naphthalene) and also from the pvc channel (DEHP). Similarly, they are present in great quantity in the wastewater of the 30 tanneries. Lastly, the analysis of the volatile compounds (Figure 3) indicates the presence of aromatic compounds (benzene derivatives) and of tetrachloroethylene, the latter being present in the majority of cases.

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