Acetoin is a precursor to diacetyl in e-cigarette liquids

Area of Science:

• Analytical Chemistry
• Environmental Health
• Toxicology

Background:

• Concerns exist regarding respiratory diseases linked to e-liquid flavorings like diacetyl and acetyl propionyl.
• Acetoin, a less toxic alternative, is also prevalent in e-liquids.
• Understanding the chemical behavior of these compounds in e-liquids is crucial for vaper safety.

Purpose of the Study:

• To investigate the chemical stability and reactivity of acetoin, acetyl propionyl, and diacetyl in e-liquids.
• To determine if acetoin can generate diacetyl under typical e-liquid storage conditions.
• To assess the impact of nicotine and pH on the degradation and formation of these flavorings.

Main Methods:

• Chemical analysis of e-liquid samples containing acetoin, acetyl propionyl, and diacetyl.
• Monitoring compound concentrations over time under various conditions.
• Investigating the influence of nicotine and pH on reaction kinetics.
• Proposing reaction mechanisms for observed chemical transformations.

Main Results:

• Acetoin, acetyl propionyl, and diacetyl are reactive in e-liquids, with concentrations decreasing over time.
• Acetoin significantly generates diacetyl in e-liquids, independent of contamination.
• Diacetyl formation from acetoin is proportional to acetoin content, increases over time, and is accelerated by nicotine.
• E-liquids stored for 18 months showed significant diacetyl and reduced acetoin, confirming acetoin as a long-term diacetyl source.

Conclusions:

• Acetoin serves as an unavoidable source of diacetyl exposure for e-cigarette users.
• Acetoin, acetyl propionyl, and diacetyl represent avoidable hazards for vapers.
• E-liquid manufacturers are advised to discontinue the use of these flavorings in formulations.