Suppose in Brine shrimp lethality tes of phytochemicals, no death of shrimps observed at all tested concentrations. What would be the LC50 of the sample?
You chose wrong concentrations. Try higher ones. You should have one concentration with no mortality, one with 100% mortality, and 4-5 concentration in between. Then you can calculate lc50
LC50 is the amount of a substance that would kill 50% of the test animals during a pre-determined period (usually 24 or 96 h). So if no mortality was observed, it is not possible to estimate the LC50. You should repeat the test with higher concentrations.
The ideal would be to make a concentration adjustment (higher concentrations), and redo the entire experiment.
If LC50 is not comes under your selected concentrations then you need to select higher concentrations range. First of all range finding bioassays were performed to calculate LC0 (maximum 0 % mortality) and LC100 (minimum 100% mortality) values. Then choose different concentrations between LC0 and LC100 values and note the concentration dependent increase in mortality. Finally probit analysis were used to find out LC50 value of the selected compound.
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