How do you mean, standards for quantitative measurements?

If you just want to get concentrations out of EPR spectra rather than arbitrary units, all you need is to calibrate the EPR machine with a stable radical. Use TEMPO or its derivatives to build a calibration curve in a certain range of concentrations.

Then, you'll need to 1) simulate the spectra using WinSIM or WinEPR; 2) double-integrate the simulated spectra; 3) use these numbers of double integrals of TEMPO spectra to build the calibration curve.

You'll also have to double-integrate the actual experimental EPR spectra. This is because it is practically impossible to correctly integrate the experimental EPR spectra due to the noise.

How do you mean, standards for quantitative measurements?

If you just want to get concentrations out of EPR spectra rather than arbitrary units, all you need is to calibrate the EPR machine with a stable radical. Use TEMPO or its derivatives to build a calibration curve in a certain range of concentrations.

Then, you'll need to 1) simulate the spectra using WinSIM or WinEPR; 2) double-integrate the simulated spectra; 3) use these numbers of double integrals of TEMPO spectra to build the calibration curve.

You'll also have to double-integrate the actual experimental EPR spectra. This is because it is practically impossible to correctly integrate the experimental EPR spectra due to the noise.

Yury, yes I need to calculate spin concentrations. The standard itself is the issue. Typically one might use copper sulfate or manganese chloride dissolved in, say, 1:1 water/glycerol at 10-1 mM, frozen with liquid nitrogen to create a glass, and measured to establish a calibration curve. The problem is I am not able to freeze my standard. I need to measure these standards at room temperature, and water/other solvents I have looked at are too lossy to measure at RT. Basically I need a solvent that is not lossy that can dissolve copper sulfate/manganese chloride/other common stable radical used for EPR.

Personally I use TEMPO as my standard as nearly everyone knows the structure of the radical, there is only one radical per TEMPO molecule, and since your radical is organic you will want to use an organic standard (at least that's my opinion)... I typically use benzene, carbon tetrachloride, or chloroform as the solvent since they don't absorb microwaves and you do not have to freeze it so they are ideal. Just seal it under argon(or nitrogen) and you should be fine. If you don't have TEMPO in your lab, go talk to a polymer group at your university and you should be able to get some. You probably only need 10mg max so they shouldn't have a problem.. As for the rest, Yury gave a good explanation on quantitative EPR. Good luck!

Is there a specific solvent purity I should be using? Is reagent grade benzene, chloroform, etc. alright to use or do I need HPLC grade solvent?

Reagent grade solvents should be fine, but obviously HPLC grade is going to be of higher purity. Just keep it consistent.

Hi Danny,

its always worth to have a look at that book for related issues:

Eaton, Gareth R., et al. Quantitative Epr. Springer Science & Business Media, 2010.

Unfortunately, there are many things to consider in quantitative EPR, like sample position, filling factor, etc... Maybe you can just work out a scheme from that. In principle, you can use TEMPO, BDPA or DPPH as a standard and for sure there are also more opportunities for spin counting reference samples ...

I agree with the issues Yury pointed out. Double integration is a central tool for the determination of spin concentrations and you have to try to record as noiseless as possible, otherwise the DI routines fail. As Baillie suggested, you should try to start with a TEMPO calibration curve and then move on to fit your needs !

Good luck and best wishes,

Joerg