Development and validation of a routine method for organotin speciation in environmental samples [Développement et validation d'une méthode de routine pour la spéciation des organoétains dans l'environnement]
Résumé
In the eighties, the organotins have been recognised for the first time as responsible of very serious environmental contamination and the European Community has listed them as priority pollutants. The toxic effects of organotins widely depend on the number and nature of alkylated or arylated groups bonded to the tin atom. Recently they have been considered as possible endocrine disrupters by the European Community (JO no L33I 15/I2/01). Negative effects on environment can occur since sub ng(Sn)L-1 concentrations. In these conditions, the development of analytical method able to speciate and detect these compounds at low concentration levels in the different parts of the environment appears essential. Such a method has been developed in our laboratory. It combines a separation step by gas chromatography (GC) with elemental selective detection using a pulsed flame photometer (PFPD). Before chromatographic injection, a derivatisation step has to be made in order to convert the analytes into thermostable forms, with preservation of their original speciation. Simultaneously, an extraction from the aqueous medium (i.e. water sample or aqueous acidic extract from solid samples) is performed by organic solvent. So, liquid/liquid extraction is used according to the standard project ISO and the French Analytical Standard Organisation AFNOR. The analytical method of determination of butyl-, phenyl- and octyltin compounds has been validated according to the recommendations of the standard XP T 90-210. This procedure is usually used to determine the performances of an analytical method, according to standard ISO 17025. It consists on four designs of handling in order to characterise the linearity, the limit of detection, the limit of quantification, to control the matrix effect over the method and to estimate the repeatability and reproducibility. This procedure was applied on aqueous solutions and solid sample as sediment. The method gives limits of detection ranged over 0.1-0.6 ng(Sn)L-1 in water, and 0.4-1 ng(Sn)g -1 in sediment samples. No matrix effect has been detected in water and sediment samples studied. The repeatability of the method is constant, efficient and accurate. A reproducibility study in sediment sample has also been done with several laboratories. It will be used by AFNOR in order to develop an analytical standard for the speciation of organotin in soils or sediments. In this case, the method developed and presented here can be considered as a simple alternative to the ISO standard project. Owing this method, the control of the environmental quality and waste water conformity can be made easily.