Table 1: Typical redox reactions of the solvents expected to occur in the electrospray emitter and their corresponding standard potentials.

Solvent systemsPositive-ion modeNegative-ion mode
Oxidation reactionsE 0 (V)Reduction reactionsE 0 (V)

Water2H2O = O2 + 4H+ + 2e1.232H2O + O2 + 4e = 4OH0.40
2H2O = H2O2 + 2H+ + 2e1.77H2O + + e = H + OH0.20
H2O = HO* + H+ + e2.72H2O + H + e = HO* + 2OH0.18
2H2O + 2e = H2 + 2OH0.07
2H2O + O2 + 2e = H2O2 + 2OH−0.13
H2O + O2 + 2e = H + OH−0.83

MethanolCH3OH = HCHO + 2H+ + 2e0.23CH3OH + H2O + 2e = CH4 + 2OH−0.25
CH3OH + H2O = HCOOH + 4H+ + 4e0.10CH3OH + 2H+ + 2e = CH4 + H2O0.58
HCOOH = CO2 + 2H+ + 2e−0.20