Photochemical Transformation of Nicotine in Wastewater Effluent

Nicotine
is a highly toxic tobacco alkaloid that is ubiquitous
in wastewater effluent. For the first time, we report the identification
of the products and the pathways for the photodegradation of nicotine
in an effluent matrix under simulated solar irradiation. Nicotine
was found to be degraded by triplet-state organic matter (3OM*), thus indicating that electron transfer is a preferred reaction
mechanism. Using the multivariate statistical strategies orthogonal
projection to latent structures discriminant analysis (OPLS-DA) and
hierarchical clustering, 49 potential transformation products (TPs)
of nicotine were successfully extracted from the water matrix via
high-resolution ultrahigh-performance liquid chromatography–quadrupole
time-of-flight mass spectrometry (UHPLC–QTOF-MS). Overall,
30 TPs, including 4 groups of nonseparated isomeric photo TPs, were
identified with various levels of confidence based on the tandem mass
spectrometry information on standard compounds and the isotope-labeling
method (using rac-nicotine-2′,3′,3′-D3, rac-nicotine-13CD3, and rac-nicotine-D4) under air-saturated conditions. The pyrrolidine ring of
nicotine was found to be the reactive site under sunlight irradiation.
Pseudooxynicotine was the main primary TP from nicotine, with a maximum
transformation ratio of 64%. Nicotinic acid, cotinine, 3′-hydroxycotinine,
and myosmine were the final stable TPs after 72 h of solar irradiation,
with yields of 13%, 3%, 5%, and 5%, respectively.