Determination of pyrazine flavourants in electronic cigarette cartridges and liquids by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GCMS)
The purpose of this study was to implement HS-SPME-GCMS, used for profiling volatile and semi-volatile compounds in tobacco products, to electronic cigarettes and e-liquids for the determination of four targeted analytes; 2,3,5-Trimethylpyrazine (TriMPZ), 2,3,5,6-Tetramethylpyrazine (TetraMPZ), 2-Acetylpyrrole (APL) and 2-Acetylpyrazine (APZ). These compounds are alkyl or acetyl-substituted derivatives of pyrazine and pyrrole, which occur as natural flavour constituents in foods and tobacco. The challenge was to minimize the impact of the high levels of the major components of the e-liquid (propylene glycol, glycerine, nicotine) on the repeatability of the analysis for these flavourants.
The test sample was placed into a 10 mL headspace vial. Two (2.0) mL saturated KCl aqueous solution was added to increase the extraction efficiency (“salting-out”) of the volatile and semi-volatile components. Ten (10) µL of ISTD solution containing d5-2-ethylpyrazine (used for TriMPZ and TetraMPZ) and d7-quinoline (used for APL and APZ) was then added to the vial. Extraction of the headspace onto a DVB/CAR/PDMS fiber occurred for 20 min at 50 °C. The fibre was desorbed onto the GC inlet for 5 min at 260 °C. Chromatographic separation was achieved using a 30 m × 0.25 mm × 0.25 µm DB WAX column. Mass spectrometer was operated in full scan mode (35-400 m/z) with the following ions used for quantitation: 122 for TriMPZ and APZ, 136 for TetraMPZ, 109 for APL.
Matrix matching to the major components of the e-liquid was found to be necessary for the calibration model since propylene glycol demonstrates significant suppression on the sensitivities of all analytes. Linearity ranged from 1-1000 ng for TriMPA and TetraMPZ, and 10-10000 ng for APL and APZ with an r2>0.999. With the same matrix matched e-liquid spiked onto blank collection pads, calibrations for the analysis of particulate phase aerosol were also achieved with the same procedure.