Question

JUL). 7.5 X6 M (5.00 mL) 7.50 x O M Van have an unknown mixture of two organic compounds, Wrenoflavin and Since whose absorbance spectra are shown below. You have a stock solution of known concentration for each compound available. Suggest a way to analyze this mixture to determine the precise concentration of each component. Absorbance Absorbance 500 510 520 530 580 590 600 500 510 540 550 560 570 Wavelength (nm) 520 530 570 580 590 600 540 550 560 Wavelength (nm) Wrenoflavin Sincoffophyll

Please help

Answer 1

One good thing you can notice about both the compounds that, one compound does not absorb at all, at the maximum absorption wavelength of the other. Wrenoflavin does not absorb at 570 nm and so does not Sincoffophyll at 530 nm. So, we can observe the absorbance at different wavelengths and they will only due to the concentration of the corresponding compound only.

Now, from the stock solution of Wrenoflavin, we can make solution of known concentrations by various dilution factors and measure the absorbances of them at $\lambda _{max}=530nm$ . From the Lambert-Beer law, we know, $A=\epsilon bC$. So, plot of A vs C will be a straight line passing through the origin. This line is called the calibration curve. Now, we'll measure the absorbance of unknown mixture solution at that wavelength. So, from the calibration curve we'll get the corresponding concentration of that species in the solution.

The same work can be done for Sincoffophyll. But for this case the $\lambda _{max}$ should be 570 nm.