Are reactive oxygen species generated in electrospray at low currents?

Area of Science:

• Electrochemistry
• Biochemistry
• Analytical Chemistry

Background:

• Electrospraying (ES) is a technique used for various applications, including aerosol generation and surface modification.
• Understanding the physical and chemical processes occurring during ES is crucial for optimizing its use.
• The generation of reactive oxygen species (ROS) during ES and their impact on biological molecules are of significant interest.

Purpose of the Study:

• To investigate the conditions under which electrospraying of solvents occurs without light emission.
• To identify and quantify reactive oxygen species (ROS) generated during electrospraying.
• To assess the impact of electrospraying on enzyme activity and the protective role of EDTA.

Main Methods:

• Electrospraying of 96% ethanol and water from a glass capillary.
• Monitoring current-voltage characteristics and light emission to detect corona discharge.
• Quantifying ROS (H2O2, O3, OH, O2-) using chemical assays.
• Assessing jack bean urease activity before and after electrospraying, with and without EDTA.

Main Results:

• Electrospraying proceeded without light emission below critical current thresholds (e.g., <100 nA for ethanol, <40 nA for water).
• Breaks in current-voltage slope indicated corona onset but were not exclusive indicators.
• Hydrogen peroxide (H2O2) and ozone (O3) were the primary ROS generated at 150-200 nA.
• Electrospraying urease at 200 nA inactivated the enzyme, an effect prevented by 0.1 mM EDTA.

Conclusions:

• Electrospraying can be controlled to avoid light emission by managing current levels.
• Specific ROS, H2O2 and O3, are produced during electrospraying at higher currents.
• Enzyme inactivation during electrospraying is linked to ROS generation and can be mitigated by chelating agents like EDTA.