The Degradation of Omeprazole in an Aquatic Environment
Linc Rhodes, Class of 2014
The presence of pharmaceuticals in aquatic environments like lakes and rivers is a
significant environmental concern. Pharmaceuticals are manufactured with specific
functional groups meant to cause chemical reactions in the human body, and in an aquatic
environment, these compounds may react in ways that are detrimental to local ecosystems.
This issue is complicated by the fact that pharmaceuticals may degrade or mutate in the
environment. Through the process of direct photolysis, compounds may absorb ultraviolet
light from the sun. This light absorption causes the formation of reactive radicals, which can
easily mutate or degrade into new compounds. These degradation products may be more
environmentally harmful than the parent compound. For this reason it is important to
understand what these drugs could degrade into with ultraviolet exposure, and how
efficiently the degradation will occur. The compound of interest for this study is omeprazole,
a proton pump inhibitor that is used to treat peptic ulcer disease and gastroesophageal reflux
disease. Used under the brand names Prilosec and Nexium, omeprazole is one of the most
heavily manufactured drugs in the world, and in 2011, it was the 3rd highest grossing drug in
the United States. As wastewater treatment plants are not 100% effective, it is almost
impossible to keep a highly produced, over-the-counter drug like omeprazole out of the
aquatic environment. The goal of this study is to both determine how efficiently omeprazole
degrades when exposed to ultraviolet light and characterize the degradation products of
omeprazole. The degradation efficiency is determined by a compounds quantum yield,
which is the number of molecules degraded per UV photon absorbed. The omeprazole was
diluted to a 50 micromolar concentration, and then exposed to ultraviolet light using a UV
photoreactor. The 350 nm UV bulbs used in the photoreactor simulate the ultraviolet light
spectrum of the sun. A sunlight actinometer standard with a known quantum yield was also
exposed to the UV radiation. The actinometer used was (PNA) mixed with pyridine. The
radiated samples were then analyzed with a photo diode array high performance liquid
chromatographer (HPLC). Taking into account the degradation rate of omeprazole
calculated from the HPLC results and the known quantum yield of the actinometer, the
quantum yield of omeprazole was calculated at 0.315. This means that when an omeprazole
molecule absorbs an ultraviolet photon, it has a 31.5% chance of degrading. This is a very
high quantum yield, showing that omeprazole is very sensitive to UV radiation in comparison
to other compounds. This result makes it even more important to know the degradation
products of omeprazole, as they as formed more efficiently than expected. Product
characterization of omeprazole is ongoing. The current techniques being utilized to
determine these products include nuclear magnetic resonance (NMR), liquid chromatography
mass spectrometry (LCMS), and UV-Vis spectroscopy. Once these products are determined,
their environmental potency will be evaluated.
Faculty Mentor: Soren Eustis
Funded by the James Stacy Coles Research Fellowship