Electrospray Ionization Mass Spectrometry: A Technique to Access the Information beyond the Molecular Weight of the Analyte : Table 1

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


Solvent systems	Positive-ion mode		Negative-ion mode
Solvent systems	Oxidation reactions	E ⁰ (V)	Reduction reactions	E ⁰ (V)

Water	2H₂O = O₂ + 4H⁺+ 2e⁻	1.23	2H₂O + O₂ + 4e⁻ = 4OH⁻	0.40
	2H₂O = H₂O₂ + 2H⁺+ 2e⁻	1.77	H₂O + + e⁻ = H + OH⁻	0.20
	H₂O = HO* + H⁺+ e⁻	2.72	H₂O + H + e⁻ = HO* + 2OH⁻	0.18
			2H₂O + 2e⁻ = H₂ + 2OH⁻	0.07
			2H₂O + O₂ + 2e⁻ = H₂O₂ + 2OH⁻	−0.13
			H₂O + O₂ + 2e⁻ = H + OH⁻	−0.83

Methanol	CH₃OH = HCHO + 2H⁺ + 2e⁻	0.23	CH₃OH + H₂O + 2e⁻ = CH₄ + 2OH⁻	−0.25
	CH₃OH + H₂O = HCOOH + 4H⁺ + 4e⁻	0.10	CH₃OH + 2H⁺ + 2e⁻ = CH₄ + H₂O	0.58
	HCOOH = CO₂ + 2H⁺ + 2e⁻	−0.20