We calculated the EC50 value based on the measured concentration after 72 or 96 hours exposure not on the nominal concentration. But I have been using oxidizing biocide like chlorine, the concentration was below detectable limit after 6 h exposure. In this case how do I calculate the EC50 value? Am I supposed to calculate it for 6 h (EC50-6h)?
You could either use the nominal concentration to calculate from or calculate the Ct (concentration*contact time) the same way it is done in disinfection. To do this you need to measure your disinfectant/oxidant concentration profile with time and integrate the curve to get the area under the curve which will be your exposure with the unit "min*mg/L".
If you are interested I can help with the data treatment.
Did you get reasonable calculations of LC50 with C*t as dose parameter?
Yes Dr. Henrik.. I feel calculating using Conc n Contact time is reliable and reasonable .. thanks a lot.
If the chemical tested will not present in water after 96 hours you will have two options. Or you make a test renewing the test solutions each 6 or 24 hours or you make the calculation only at the time you have the chemical in water.
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