[TTAGGGn]

How do I determine the uncertainty in the concentration, absorbance, and molar absorptivity?

A= 0.47623
b = 1 cm
c = 100mM

molar absorptivity = absorbance/(path length of cuvette x concentration)

e = A/(b*c) = 0.47623/(1cm*100mM) = 0.0047632 cm^-1 mM^-1


I think the uncertainty in the 1cm cuvette is +/- 0.1. I got this from an analytical textbook, but i'm not sure how to find the uncertainties of absorbance and concentration and the final answer for the molar absoprtivity.

I also think i have to use error propgation formulas for the final answer but i cant start that without getting the uncertainty of the concentration

[fledarmus]

How do you know what the concentration is? Did you prepare the sample? If it was commercial, there should be some indication of the error on the bottle. If you prepared it, you will be able to calculate it from the uncertainty in your mass and volume measurements. If it was just a bottle your lab instructor gave you marked "100 mM", there is really no way to know whether that should be one, two, or three significant figures.

As for the cuvette, you usually get that from the specifications provided by the manufacturer. If you are really looking for precision, you can factor in a temperature correction as well  . Okay, for anything close to room temp it is probably far smaller than the error in the measurement anyway.