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(38-28) Improved use of the photobacteria toxicity test for soil and sediment samples. Lappalainen, Juha*,1, Juvonen, Risto1, 1 Aboatox Oy, Lemminkäisenkatu 36, TURKU, FINLAND ABSTRACT- Matrix effects caused by small particles and/or colour in the sample have been major disadvantages in the photobacteria toxicity tests, if a direct contact between the bacteria and sample is required. With sediment samples the major methodological problems are loss of sensor bacteria due to adhesion to sediment particles and optical interference of suspended sediment particles. The filtering protocol can be used and it is more reliable than some other methods such as pore water or extract test, but it also has some limitations. A recently developed approach, the Flash method, shows clear advantages over previous methods. The main difference between the Flash method and other application is the use of kinetic measurement whereby the light output of the bioluminescence reaction is followed from the very beginning of the assay. The photobacteria reagent is dispenced on top of the sample and the changes in the luminescence signal are recorded at several readings per second. The maximum luminescence signal is reached immediately after dispensing the bacteria. The decrease in luminescence signal after this can only be caused by toxicity. Performance of the method with different sample types and instrument requirements are discussed. Key words: V.fischeri, Flash method, toxicity |
