How do you solve for concentration knowing absorbance?
1 Answer
Jun 8, 2016
You use Beer's law:
#\mathbf(A = epsilonbc),# where:
#A# is the absorbance of the solution. This is unitless.#epsilon# is the extinction coefficient, or molar absorptivity, of the species in solution in#"L"/("mol"cdot"cm")# .#b# is the path length of the cuvet. This tends to be#"1 cm"# for typical UV-Vis spectrometry.#c# is the known concentration of your solution in#"M"# or#"mol/L"# .
Hence, all you really need to do is solve for
#color(blue)(c = (A)/(epsilonb))#
You already have
If you have multiple absorbances, then you have multiple concentrations to solve for.
You don't really need the wavelength to calculate concentration, but you should still report that. I'm guessing it is your
Example:
That is the wavelength where the light absorption generates the tallest absorbance signal.