Figure 24.

(a) Tubes made of PDMS, Tygon, or PVC are filled with deionized water and are compressed by a vice. (b) Electron spin resonance spectrum of a solution of DMPO in THF (1 mg mL⁻¹) in the presence of compressed PDMS in an argon atmosphere (red) or uncompressed PDMS (black, the same spectrum is obtained in the absence of any PDMS). (c) A solution of DPPH (10.0  μM) changes color from purple to yellow when squeezed polymer tubes (in this case, Tygon) are added, which indicates the transformation from DPPH into DPPH−R in the presence of radicals. (d) Changes in the UV/Vis spectra of the solution of DPPH are shown over time. Reproduced with permission from Ref. [191]. Copyright 2012, Wiley‐VCH.