# Homework Help: How to get calibration curve?

1. Nov 24, 2015

### CannonSLX

I've just done an ion chromatography experiment and have normalized my data for a known sample which has a known concentration of 10ppm.

I know that the first large peak is due to F- ions and so the area of the peak is propositional to the concentration of the ion.

Given that I know the area, how can I get the calibration curve just by this information ?

2. Nov 25, 2015

### Staff: Mentor

Assume signal would be zero if there were no F- at all, that gives you two pints, enough to draw a straight line.

That's not the best approach in general, but better than nothing.

3. Nov 25, 2015

### CannonSLX

Thanks, but I'm not sure I fully understand.

This is my current data graph; https://i.gyazo.com/72d8f842cc504e924d1d0f106fb0266a.png
The first large peak corresponds to F- ions.
If I assumed the signal as 0 how would I plot a calibration curve ? Would it be possible for me to choose 2 points on the curve which produce a linear relationship ?

4. Nov 25, 2015

### Staff: Mentor

You know the area of a peak that correspond to a 10 ppm concentration, yes?

Assume 0 ppm would produce no peak - or a peak of area 0.

That gives you two points for calibration curve - one for 0 ppm concentration and one for 10 ppm concentration.

5. Nov 25, 2015

### CannonSLX

I see, thanks.

To calculate the area, can I normalise my data so that the area under the curve is directly po
Thanks. I've managed to do it and used excel to calculate the gradient, in the form y=mx+c
One last question.

If I run a sample with an unknown concentration of F-, if I know the area under the curve (y) and the gradient (m), knowing that c=0, would I just solve for (x) which would be my concentration of F- in the unknown sample ?

6. Nov 25, 2015

### Staff: Mentor

You lost something here. You can use peak height instead of the area, typically these are related (and in the case of a nice curve - like the one you have - it is quite good approach).

Yes.

7. Nov 25, 2015

### CannonSLX

We've been told to use area, so would normalising be the right idea for this approach ?

8. Nov 25, 2015

### Staff: Mentor

If you are told to use area - use area.

9. Nov 25, 2015