Non quantal test

It is possible to use a preliminary dilution step of 1 100 when the pT-scale relies, for instance, on a < 20% effect endpoint measurement (e.g., determination of IC < 20 in non quantal tests with algae and bacteria). In this case, the pT-value should be calculated from the concentration-effect curve. The pT-value is determined by using the first sample concentration that generates an effect below 20%. If, for example, the concentration incurring a 19% effect is equated with a dilution factor of 1 3200, the pT-value is calculated with equation 5 as demonstrated below. The modulus for transforming decadic logarithms into binary ones, 1 / logio 2 , yields equation 6. For the 1 100 diluted wastewater example above, the pT-value can then be calculated with the help of equation 8. 

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