Three substance absorbe light in the un/visible region. In determining the concentration of these three substances which are present in the same solution using spectrophotometry (without prior separation) what condition must apply?

Answer 1

You want each solution to absorb at a specific wavelength that the others two substances have no absorbance. However, IF you have the three spectra and can make standard solution, it IS possible, with a good bit of work, to set up simultaneous equations (or use successive approximations) to solve for one if the spectra do overlap.