[sutucon15081995]

I have a bunch of analytical chemistry questions, any help is greatly appreciated.
1) a) 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?

I was given excitation spectrum of A and fluorescence spectra of solution #1 to #6

So far, I come up with this
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

Then I plot a graph between fluorescence intensity vs concentration. Now I am stuck there
b) If a synchronous experiment is to be performed what would be the offset that you use?
2) It is not necessary to determine the wavelength range in synchronous experiment, why>
3) List advantages of synchronous run compared to excitation and emission spectra in fluorescence

[Arkcon]

I'd like to welcome you, sutucon15081995: to the Chemical Forums.  According to the Forum Rules{click}, we want to see your attempt, so please click on that link, read the contents, and comply with our rules, so we can help you. 

Your questions are simply definitions.  We can't help with definitions -- you'll either read them in your text, class notes or lab instructions, or we'll look them up for and just tell you.  And we don't do the second one.

You're asked to determine concentration from signal, and you're correct that you need to plot it.  Did you plot your data?  How did that work?

[sutucon15081995]

Hi, Thank you so much. For question 1, after calculation 6 concentrations of my unknown, I plot that concentration vs fluorescence intensity (at wavelength = 472nm )
My data is something that looks like this
Sample    Concentration     Intensity
1              0.0                    9.990
2              1.5                    19.979
3               3.0                   29.986
4              4.5                     39.958
5               6.0                    49.947
6               7.0                     60.000
My calibration plot gives equation
y=6.6656x+9.9777
R^2=1
I totally stuck from here.
I am thinking about the way that I will take the highest intensity in excitation spectra which is 100 and then plug it in.

I also stuck for b. Any help is greatly appreciated

[Hunter2]

This is standard addition.  You check your plot where the graph intersect the x-axis. Somewhere in the negative side. This value gives your amount of your sample as positive value.

[sutucon15081995]

Hi Thank you Hunter2
So you mean I do not need to use the intensity from excitation spectra?
In addition, do you have any idea about "If a synchronous experiment is to be performed what would be the offset that you use?"