[blast_]

Considering the following equations:


D= b(E'xE''y - E''xE'y)

I need to determine the concentration of benzoic acid and caffeine in different beverages.

Here are my graphs of my standards:



I know my slopes are the epsilon values(molar absorptivities), but I don't know which ones to assign to E'x,E''x,E'y, and E''y. (E = epsilon)

Also... Here are my absorbances at wavelengths 230.1 and 275.1. 



I'm pretty sure I use:
A'= .9234
A''= .4061
for determining concentrations for mountain dew.

I've tried it a million different ways and I'm getting concentrations of caffeine like 11.442M, 22.01M, and other concentrations that are outrageous.  I'm definitely doing something wrong.  Can someone help?

Thanks!!!

[FeLiXe]

did you consider the benzoic acid absorption?

these things come down to a linear equation system

A1 = cA*epsA1 + cB*epsB1
A2 = cA*epsA2 + cB*epsB2

where A and B are your substances, 1 and 2 the wavelengths
the epsilons you get from your regression
A1 and A2 from your measurement in mountain dew

[ARGOS++]

Dear Blast_;

IMHO –  Forget this Experiment!, as sooner as possible the better,  except you have in mind to redo the whole work with much better preparation and measuring conditions!
Sorry!

I have redraw one of your calibrations with a little better “View” in the Attachment!
I don’t know you are already able to see the whole Disaster.

The second picture shows the same; expect that I “corrected” two measuring points of your calibration.
It is still the same dilemma, but it’s a little bit “closer” to your wrong Measuring-Reality!

I have in the moment to leave for a few Hours, but after I will have time for a more detailed discussion.
(Sorry for this delay!)


Good Luck!
                    ARGOS⁺⁺

[ARGOS++]

Dear Blast_;

Do you have already any Assumption what may went wrong?

Good Luck!
                    ARGOS⁺⁺