This post will be very scientific, but I will write the introduction suitable for everyone.
If you read my post devoted to free radicals you know that there are two kinds of free radical: stable free radicals and unstable free radicals.
You also know that not all the radicals are the same in the meaning of its reactivity.
Consequently, different radicals can't be stopped using the same molecules/ enzymes or whatever comes to your mind (destruction of the precursors of the reaction).
In other words, Antiox labels on your food are not pure, but partial fantasy.
If you missed that post, you can find it here
How we detect free radicals - EPR spectroscopy?
Source
The device you see in the picture above is the EPR spectrometer, the device very similar to NMR or the MRI.
If you take any EPR book, it probably starts like this:
EPR is the technique analogous to the NMR. All equations are the same and the principle of work is also the same
There are two main components of the EPR: good electromagnet and the source of microwaves (yes, microwave oven or radar, depending on your preferences).
Source
Resonant condition is defined by the values of the magnetic field and the frequency of microwaves.
Just as in radar technology, we are also naming the EPR in "bands". The most common devices are X-band spectrometers.
L-band spectrometers can be used for larger samples (several cm), but the resolution is poorer/
High-frequency spectrometers are mainly custom made and can have the frequency even up to 500 GHz.
Higher frequency = better resolution on the x-axis.
From my thesis, no source :)
It is very obvious that you can achieve the resonance conditions in two ways: by changing the frequency or by changing the magnetic field.
So... There will be two types of EPR, CW (constant wavelength) or pulsed (constant magnet).
Pulsed devices are much more expensive, but can give us the insight into the microenvironment of the radicals, using various sequences.
Just as an example, I showed you the HYSCORE experiment. The elements on the left and the right quadrant slow week and strong coupling.
Image
The spectra obtained from the CW-EPR are less informative but still useful.
There are 3 parameters, signal height (amount of radical), signal width (rough structure) and the position called the g-value (what is the core radical)
This is DPPH radical, known in antioxidative tests:
Source
How it looks like in practice?
For the stable free radicals, the procedure is incredibly simple - you put the sample.
Seriously, no preparation, nothing, you put the sample into the cavity.
Liquid, solid, gas, powder - just put it as it is.
If you want, you can irradiate it with UV, change the atmosphere, do kinetics or play with the temperature.
Short-lived radicals?
Well, those are much more tricky.
In order to examine them, you need to use the spin-trap.
The most common one is the DMPO, capable to trap multiple species of free radicals and produce the unique signals for each one of them.
I prefer to use DEPMPO that has the phosphorous molecule and one more splitting of the lines.
My spectra look like this:
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Based on the distance between the lines and the pattern, it is possible to determine the family of free radicals.
For example, I can see the difference between *OH and *R, but I can't tell the difference between *CH3 and *CH2CH3.
Price?
Spectrometers cost somewhere between 20.000 for the bench-top model made in Belarus/ Ukraine to about 100.000 for the very good basic model to about a 1.000.000 if you buy all the accessories.
Experiments with stable radicals are - free.
DMPO costs several $ per experiment.
And the DEPMPO costs Steem $ per experiment.
EPR - MRI, does it exists?
Yes, but the technology is still young.
There is EPR imaging, completely analog to MRI/NMR, but the resolution is... Poor.
Source
There is the possibility to use MRI + EPR Imaging, in the way that MRI makes good spatial resolution and EPR Imaging is used as the mask.
Conclusion
If you see that some product advertises the juice that reduces free radicals in your liver - walk away.
All that we can say in 2017 is if some substance prevents the production of free radicals in-vitro.
Procedures for in-vivo measurements are possible for publishing but not in a daily routine.
If you are the professional
Be free to contact me for any form of collaboration.
I have the experience with the food, extracts, cells in culture, Tardigrades (the first ever), petrochemical products (maybe the first ever, confidential), plants and small animals (including the bacon).