Any help is greatly appreciated
5mL of a solution A (unknown concentration) was transferred into sic 25mL volumetric flask. The following volumes of a standard solution of A with with a concentration 75ppm were added to the flask: 0mL, 0.5mL, 1mL, 1.5mL, 2mL, and 2.5L. The excitation spectrum and and emission spectra is provided. Determine the unknown concentration of A in that solution?
So far, I have come up with this solution
- I first calculated the concentration of standard solution. Please help me to check if my calculation is right
Stard 1: 0
Stard 2: 0.5*75ppm/25=1.5
Stard 3: 1*75/25 = 3
and so on
- Then I use Excel spreadsheet to make a best fit line between concentration and fluorescence intensity. The intensity would be a number which has a highest emission value
My equation is y=7.617x + 4.7449 and R^2=0.9797
-From the excitation spectrum, the wavelength at which maximum intensity is obtained is 375nm
-From the emission spectrum, the wavelength at which there is maximum fluorescence is 472nm
Now I am stuck. I do not know how to find the fluorescence intensity of the unknown solution to plug it in the equation.
One more question, my R^2 value is not really close to 1, should I omit some value to make a perfect line?
Thank you in advance for any help
6 answers
As for R, that looks pretty close to 1 to me.
http://en.wikipedia.org/wiki/Standard_addition#/media/File:Standard_addition.gif
However, I feel like this method requires absorbance to plot a graph. Unfortunately, My question does not provide any absorbance data.
If you want to pursue this further I recommend you start a new thread and repost the question at the top of the page but provide answers to the above.