Ascorbic acid for homogenous redox buffering in electrospray ionization-mass spectrometry

Area of Science:

• Analytical Chemistry
• Electrochemistry
• Mass Spectrometry

Background:

• Electrospray ionization (ESI) is a crucial technique for generating ions for mass spectrometry.
• Electrochemical reactions within the ESI source can alter analytes, complicating identification and quantification.
• Controlling electrolysis is vital for reliable ESI-MS analysis.

Purpose of the Study:

• To evaluate the efficacy of antioxidants for suppressing electrochemical oxidation in positive ESI.
• To identify a simple, inexpensive, and efficient method for redox buffering in ESI.
• To assess the impact of antioxidants on analyte ionization and spectral quality.

Main Methods:

• Tested ascorbic acid, hydroquinone, and glutathione as redox buffers in positive ESI.
• Analyzed pharmaceutical compounds with varying functional groups prone to oxidation.
• Employed continuous infusion, flow injection, and liquid chromatography/mass spectrometry (LC/MS).

Main Results:

• Ascorbic acid demonstrated superior antioxidant activity compared to hydroquinone and glutathione.
• Ascorbic acid exhibited a stable oxidation product and minimal impact on analyte ionization.
• Ascorbic acid suppressed sodiated adduct formation and induced charge state reduction.

Conclusions:

• Ascorbic acid is a highly effective antioxidant for positive ESI, enhancing analytical reliability.
• Its use simplifies sample preparation and improves the quality of mass spectrometry data.
• Potential interference exists only when analyzing compounds isobaric to ascorbic acid.