In school we did two different experiments to decide the amount of iron in parsley.
I have got two very different values(one is 61ppm and the other is 36ppm) and therefore I wonder If it's my calculations are correct or if it was something that went wrong during the lab.
First of all 0,1 liters parsley solution were created that were used during both experiments .
First with Atomic absorption spectroscopy(AAS)
I made a function of how the absorption(abs.) was depending on the c[g/liter] Fe with 4 different calibration solutions.
abs. = k*c+m
k=12,15 and m=-0,0002
c = (abs.+0,0002)/12,15
and then to decide the mass of the parsley with c*V where V were 0,1 liters(The amount of parsley solution). This is correct right?
I think this is right because I got the amount of Iron to around 36ppm which is very close to what livsmedelsverket(Swedish food controllants) got it to.
However with my spectroscopy lab something probably went wrong.
In a similar manor to the one in the last experiment a function was created this time with the concentration of Fe in [M].
abs. = 6395,1421*c - 0,02
In our 4 calibration solutions this time we had FeCl3
HCl and KSCN. (So it turned red)According to this picturehttps://gyazo.com/05d69ca7188c27ea95830d307fa098a4
We also made one solution with nothing but 2,00cm3
distilled water and 1,00cm3
Lastly we took 2,00cm3
parsley solution and added 1,00cm3
KSCN. (so it turned red).
We put 3,00cm3
of every solution in different cuvettes and the parsley solution abs.=0,169
Now I will try to explain how I calculated the mass of Fe.
c = (abs. - m)/k //this is c Fe in the cuvette.
n Fe = n FeSCN63-
= c*V1 were V1 = 0,003(Total amount of solution in the cuvette) right?
then to get the concentration of Fe in the parsley solution, c1, you divide c*V1 with V2 were V2=0,002 (amount of parsley solution in the cuvette). //This and the step above is what I'm a little unsure about If you're acculy supposed to do them at all.
Since c1 is the concentration of Fe in the parsley solution you multiply it by the total volume of parsley solution(0,1liters) and then with Molar mass, M, of Fe (55,845).
c1*Vtot*M = mFe //this should be right
And then when I calculate the ppm of Fe in the same parsley I get 61ppm.
I think that something went wrong during the laboration but If someone understands my formulas, please try to see if I calculated something wrong or if something went wrong during the laboration.