Enantiomeric separation of N′-nitrosonornicotine by capillary electrophoresis Original Research Article

N′-Nitrosonornicotine (NNN) is the most abundant tobacco-specific nitrosamine (TSNA) found in tobacco and tobacco smoke, and is formed by the nitrosation of nicotine, amongst other possible mechanisms. Tumor induction is believed to occur by way of 2′-hydroxylation of NNN, and others have shown that (S)-NNN undergoes significantly more 2′-hydroxylation than does (R)-NNN. As such, there is a need to be able to separate and quantify the two enantiomeric forms of this important analyte. In the current work, we present a simple capillary electrophoresis method capable of achieving the desired separation. By employing uncoated, fused-silica capillaries with a citric acid buffer (pH 2.8) containing hydroxypropyl-β-cyclodextrin (HP-β-CD), the (R)- and (S)-forms of NNN are resolved in about 4 min. The identities of the two enantiomers were confirmed by comparison to reaction products from the nitrosation of an (S)-(−)-nicotine sample. Furthermore, this method was applied to a crude tobacco extract to establish its potential for resolving NNN enantiomers from a complex mixture containing more dominant tobacco alkaloids.