How is molar absorptivity used to determine concentration from absorbance?
A = ebc.
A = Absorbance
e = molar absorptivity = constant
b = cell length
c = concn in mols/L
Measure A of a known concentration. Knowing b and c, solve for e. Then measure A of an unknown. Plug in b and e, solve for c in mols/L. Convert to ppm or whatever units you want.