The Toxi-ChromoPadTM bioassay uses a novel mutant of the bacterium E. coli as the test organism. This bacterium was selected specifically for sensitivity to a wide range of toxic substances and is well adapted for acute sediment toxicity testing.
The assay allows the bacteria to grow in direct contact with the toxicants in the sample, eliminating expensive extraction procedures. The endpoint of the assay is an easy to interpret colour reaction. If the sample is toxic, no colour will develop; if the sample is non-toxic, a distinctive blue colour develops around the sample.
The Toxi-ChromoPadTM kit is a bioassay screening tool used to determine acute toxicity in soils, sediments, sludge or other solid waste material directly without extraction.
Each kit contains all the reagents and disposable materials necessary to test at least four samples, including dilutions and controls.
Disc 1(center dot is a control) A series of 8-2 fold serial dilutions were carried out on the pad ranging from pure sludge to less than 1%. At a concentration of 0.8% the sample showed no toxicity.
Disc 2 – The same test carried out on a different sludge sample. In this case toxicity disappeared at a 6% concentration showing this sample was 10X less toxic.