Nicotyrine

The standards of nicotine, cotinine, anabasine and myosmine and boric acid were purchased from Sigma Aldrich (St. Louis, USA). Nornicotine and ␤-nicotyrine standards were bought from Toronto Research Chemicals Inc. (Toronto, USA). Nicotine-N-oxide and anatabine came from Cayman Chemical (Michigan, USA). The matrix components propylene glycol and glycerol were purchased from Merck (Schuchardt, Germany). The components used to reconstitute a flavoured e-liquid sample were all purchased from Sigma Aldrich (St. Louis, USA). These include diacetyl, acetylpropionyl, maltol, ethylmaltol, vanillin, ethylvanillin, citral, limonene, cinnamaldehyde, transcinnamaldehyde, benzaldehyde, carvone, pulgeone, damascenone, methylcyclopentone, methylcinnamate, methylaminobenzoaat and methylmyristate. The solvents acetonitrile, methanol, acetone and ethylactetate were HPLC-grade and were purchased from Biosolve (Valkenswaard, The Netherlands). Concentrated ammonia 28-30% was obtained from Merck (Darmstadt, Germany). Water was obtained using a milliQ-Gradient A10 system (Millipore, Billerica, USA).

Nicotine, cotinine, and norNicotine were purchased from Sigma-Aldrich (St. Louis, MO) as standards. PseudooxyNicotine, nicotyrine and 6-hydroxyNicotine were obtained from Toronto Research Chemicals (Toronto, ON, Canada). All analytical and high-performance liquid chromatography (HPLC) grade reagents were bought from Merck China (Beijing, China).