EPR spectra of the gallate free radical at pH 9 and 11. The solution contains 1 mM gallic acid in 100 mM potassium phosphate with the pH adjusted by addition of NaOH. Top: This spectrum is consistent with hyperfine splittings due to three protons. The apparent hyperfine splitting constants for these three protons were determined using WinSim program, aH = 1.00 G, aH = 0.23 G, and aH = 0.28 G. Under our experimental conditions this spectrum is observed from about pH 7 to approximately pH 10. Bottom: EPR spectrum of the gallate free radical at pH 11. This 1:2:1 spectrum is described by two identical hyperfine splitting constant aH = 1.07 G (2).