Which radical, how many, and for how long
A radical gives a spectrum whose pattern identifies it. The size of the signal tells how many radicals are present, and the way the signal changes in time shows how quickly they form and disappear. Together they give a direct view of reaction mechanisms and of the lifetime of reactive species.
Where it is used
- Photochemistry, with the sample irradiated in the instrument
- Radical polymerisation and its inhibitors
- Redox reactions and electron transfer
- Antioxidants and radical scavengers
- Degradation of materials by heat, light or radiation
- Short-lived radicals, made measurable with a spin trap
Spectrum, count and time course
To identify a radical, the spectrum is recorded and its pattern is compared with known ones. To count the spins, the spectrum is integrated twice, and the final area is compared with that of a reference sample with a known number of spins. To follow kinetics, the field is fixed on a line of the spectrum and the signal is recorded against time while the reaction is started, for example by light.
What it adds
- Sees radicals directly and selectively, in the presence of everything else in the sample
- Quantitative, with a reference sample
- Follows fast and slow changes in time
- Benchtop instruments make the technique accessible to a research group
Points that matter in practice
- A radical has to live long enough to be measured, otherwise a spin trap is needed
- For counting, keep the sample position and the settings identical to those of the reference, and avoid saturating the signal
- Double integration is sensitive to the baseline, so check it carefully
- Kinetic studies need temperature control, and irradiation needs suitable access to the sample
- Solvents that absorb microwaves, such as water, call for thin cells
From your question to a routine method
Describe your system and your question. MSY Consulting runs feasibility measurements, helps you choose the conditions and the reference for counting, and supports you with the analysis until the method is part of your routine.
Let's talk about your application
Send an email describing your instrument and your application, and you will get a reply.
contact@msyconsulting.euMSY CONSULTING SAS · Wissembourg, France · LinkedIn