Comprehensive two-dimensional gas chromatography analysis of volatiles on e-liquids and aerosol compounds produced during the heating process

• Isolation and pre-concentration of VOCs using solid-phase microextraction. • Method development using central composite design. • Enhanced characterization of e-liquids using GC × GC-MS. • 126 VOCs were identified in the e-liquids, including concerning compounds. • Principal component analysis revealed the formation of harmful VOCs. Electronic cigarettes (e-cigarettes) have gained global popularity, raising public health concerns due to the limited regulation and chemical complexity of e-liquids and their aerosols. This study presents the compositional analysis of volatile and semi-volatile organic compounds in 34 commercial e-liquid samples and their corresponding aerosols using headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography coupled with mass spectrometry (GC × GC-MS). The HS-SPME method was optimized using a central composite design (CCD), which established the ideal extraction conditions. One hundred twenty-six compounds were identified in the e-liquids. Chemometric analysis revealed distinct flavor profiles. The occurrence of concerning aldehydes, including benzaldehyde and (E)-cinnamaldehyde, was confirmed in the samples. The study of compounds generated when the e-liquids were heated at various temperatures (190–270°C) and durations (3–30 min) showed the formation of harmful and potentially harmful constituents (HPHCs), including furfural, glycidol, and diacetyl, under specific conditions. Principal component analysis (PCA) of the aerosol data revealed the impact of heating time on the volatilization of both major e-liquid components and lower-concentration flavoring compounds. Overall, this study demonstrated the potential of GC × GC-MS for characterizing e-liquids and enhanced our understanding of toxic compound formation during the heating of e-liquids.