How to find concentration of three species from given molar absorptivities If I am given the molar absorptivities of three species at a given wavelength, and I only have the concentration of one of those species, how can I determine the concentrations of each of the remaining two species? The distance light travels, the molar absorptivities and the amount of light absorbed are given.
The equation you need would seem to be $\ce{A=\epsilon [C] L}$ where A is the amount of absorption (optical density), L the cell path length, your 'distance light travels' and [C] concentration. As you have 3 species absorbing at the same wavelength you have $\ce{A=(\epsilon_1[C_1] + \epsilon_2[C_2] + \epsilon_3[C_3])L}$. You know L and the $\epsilon$'s but only one of the three concentrations and therefore you do not have enough information to determine the two remaining ones.