Bestimmung von Organozinnverbindungen in Sedimenten mittels GC-AED ⎯ Entwicklung von Extraktions- und Derivatisierungsmethoden

Abstract

The analysis of organotin compounds in environmental samples is a challenging task. It is due to their partly very low levels of contamination, the diversity of sample matrices and the different nature of their organic moiety and chemical binding. In order to achieve comparable and reliable data a harmonised and standardised analytical procedure is necessary. In this work different approaches to the gas chromatographic determination of organotin compounds in sediments were further developed. Emphasis was put on the extraction of butyltin compounds from the sediment matrices, their derivatisation and their clean-up. Besides the four butyltin compounds investigations were carried out on a total of 14 organotin compounds. Another important aspect of the method development was the separation and detection of the compounds and their quantification. For the determination of the analytes in sediments an extensive sample pre-treatment and sample preparation was necessary. The choice of the extraction method, the extraction conditions, the derivatisation and the clean-up had a crucial influence on the accuracy of the results. It was shown that due to the different nature of the organotin compounds a compounddependent sample pre-treatment and sample preparation is required. Tetra-substituted organotin compounds must be determined in the original-wet and not in the freeze-dried sediment. For the quantification of phenyltin compounds the clean-up cannot be performed with silica gel/silver nitrate, which is otherwise suitable for the separation of sulphur compounds originating from the sediment matrix. For all other analytes a uniform sample preparation could be defined. Gas chromatography coupled with atomic emission detection (GC-AED) was used as the measuring method. It is selective for tin compounds and possesses a high sensitivity. The wavelength and the gases supplied to the plasma of the AED were optimized for the determination of Sn-containing compounds. The response proved to be substance-dependent. It could be shown that the intensity of the Sn-signal is affected by the matrix of the derivatisation reagent, in particular by the boron part of the reagent, and therefore a clean-up is essential. Mass spectrometry coupled with gas chromatography (GC-MS) was chosen as method of comparison. For the quantification with selective masses, the GC-MS possessed a sensitivity comparable with that of the GC-AED. The possibility of using isotope-labelled standards instead of chemical internal standards for the quantification is an advantage of the GC-MS. The results of this work were directly contributed to the standardisation.