Sample preparation for bacterial toxicity tests by means of thermodesorption

Status:

completed 10/1998

Aims:

Workplace air is often polluted by a large variety of chemical substances whose total toxicity is a result of synergistic and antagonistic effects. A method was to be developed in the framework of the project by which gaseous substances in the air can be sampled, upgraded and analysed in a bacterial toxicity and mutagenicity test in an aqueous medium. The method should be gentle such as to minimise artefacts due to work-up.

Activities/Methods:

A large range of typical workplace substances and mixtures of substances in different combinations and concentrations were sampled under defined conditions using a special adsorption tube (modified activated charcoal). Desorption of the tubes was by thermodesorption with a cold trap; the thus emitted gases were collected in dimethyl sulfoxide and ethanol. The times of loading, desorption and collection as well as the desorption temperatures were optimized. The recovery rate was quantified by use of gas chromatography/electron capture detection (GC-ECD). Toxicity of the aliquots of the DMSO and ethanol concentrations was determined in bacterial luminescence tests "Microtox" (test organism: vibrio fischeri).

Results:

The suitability of the tested method could be proven. The recovery rate varied between 77% and 96% depending on the substance under consideration. Ethanol turned out to be a better solvent than dimethyl sulfoxide. The quantities of solvents used in the tests did not falsify the measurement results obtained with the vibrio fischeri test organisms. The method still has to be validated in field tests.

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