Hach-Lange LUMISTOX 300 LPV321 User Manual - Manual (Page 39)

LUMIStox 300 Operating Manual Dr. Bruno Lange GmbH
______________________________________________________________________________
______________________________________________________________________________
Page: 39
4.4 Calculating the EC value
Definitions:
Γ:
Gamma value calculated from %Ht
Konz: Concentration of the sample in a test solution
EC50/20: Concentration of the sample in the test that causes 50% (20%) inhibition
4. Calculating gamma
Γ = %inhib.t / (100 - %inhib.t)
5. Take the
Γ
-values as the y-coordinates (ordinates) and the associated
concentrations as the x-coordinates (abscissa) and plot them in a two-
dimensional logarithmic coordinate system (range of ordinates: -0.95 to +0.95).
6. The EC50 value is given by the point of intersection with the x-axis at
Γ
= 1.
7. The EC20 value is given by the point of intersection with the x-axis at
Γ
= 0.25.