EPR Settings, How to make it less wrong

It all came spontaneously... I was chatting with @irelandscape and @dexterdev when suddenly we've got an epiphany: why not promoting https://www.stemq.io/ by answering ResearchGate Questions? Immediately after, I asked @justtryme90 how about making posts based on RG Questions and promoting https://www.steemstem.io - he agreed.

So let's start with the first one. I will boost my RG Score a bit, I will sharpen my mind - and I will do something useful for our community *(I hope so...)

> In and EPR calibration (intensity-concentration) , what does the slope mean?

> In a calibration, using the integral area related to the pattern concentration, the slope represents something. I'm having a hard time finding the answer to this issue. Any EPR experts out there? Thanks in advance!

And the answer was... Simply wrong:

> if i am not wrong, the intensity of signal represent the spin of free radical depositing on detector of EPR.

Nothing is depositing on EPR's detector! It's physically impossible because the sample is sitting in the tube, peacefully. It's not moving anywhere. Actually, in order to tune the device, it must be rock steady. No shrinking, no moving, crumbling, bubbling...

Actually... It's possible if you smoke near the spectrometer. After about 10 cigarettes, there will be some deposits in the cavity, and you will see a very nice signal of *C radical.

Before you start

check if the cavity is clean, try without the sample
use the temperature controller (not obligatory)
be sure that your sample is not changing its shape/volume/consistency

If it evaporates/shrinks, it will change the tune, and if the tune is changed - the intensity will be different.

Be sure that it's still liquid when you are changing concentration because otherwise, you can expect anisotropy and the width of your signal (integral as well) will be seriously affected.

Now, set your spectrometer properly:

Modulation amplitude must be optimal. If the value is too big, signal width will be wrong. If it's too small, your peak will be too narrow
Microwave power, very important. If you saturate it, the response will not be linear.
play with iris, apply the same tune every time
if the sample is solid, make it similar, every time.
Check if your tubes are the same and that the positioning inside the cavity is the same

If everything is fine, there are two ways how you can plot, by plotting the integral or intensity. I know very well that in the books you will find the integral, but here is the problem... If the sample remains the same, the width should be... The same...

If it isn't: you are introducing δ. (Example: your signals are 5.42 G and 5.38 G, your error is 0.1 G, don't multiply with 5.42 and 5.38!)

Or... Your sample is problematic.

I prefer to plot the width and check if the values are within the ε. If there is no trend, ok... It's the same radical. Go either with the integral or with the intensity.

It will be linear with concentration. More substance, more spins, higher the signal...