Instrumental methods of analysis I am taking the instrumental methods of analysis course. Our job is to find the unknown  mass of $\ce{Fe}$ which is added, by measuring the absorbance of different solutions with ortho-fenantroline. 

Is there any way I can know if my calculated mass of $\ce{Fe}$ is correct or not?   Is there any way I can prove it, since I know the absorbances?
Am I right that you are planning to simply calculate the $\ce{Fe}$ concentration using the Lambert-Beer equation?

The obvious proof would be to prepare $\ce{Fe}$ solutions with known concentration(s) to compare the absorbances. Using these solutions, you can also make sure that the assumption of linearity over the concentration range is actually fulfilled.