Kinetics and Degradation Products for Direct Photolysis of -Blockers in Water
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- 作者：Qin-Tao Liu ; Helen E. Williams
- 刊名：Environmental Science & Technology
- 出版年：2007
- 出版时间：February 1, 2007
- 年：2007
- 卷：41
- 期：3
- 页码：803 - 810
- 全文大小：248K
- 年卷期：v.41,no.3(February 1, 2007)
- ISSN：1520-5851
文摘
Related to improving persistence assessment of activepharmaceutical ingredients (APIs), direct aqueous photolysisof 
-blockers: propranolol (hydrochloride salt), atenolol,and metoprolol (succinate salt) were investigated by exposingthe samples (0.0003-10 mg L-1) to a solar irradiator(filtered xenon lamp: 290-800 nm) at 20-26 
C. Resultssuggested that direct photolysis in optically dilute solutionsfollowed pseudo first-order kinetics. The measured half-lives of propranolol, atenolol, and metoprolol wereapproximately 16, 350, and 630 h, respectively. Thesewere 3-5 orders of magnitude slower than the estimatedminimum half-lives. The measured half-lives were relatedto day light surface conditions by comparing the light intensityof the lamp and the sun at different latitudes and seasons.Major direct photolysis products were identified frompropranolol that led to a proposed reaction pathway, involvingring oxidation, rearrangement, and deoxygenation.Electron paramagnetic resonance (EPR) spectroscopyresults confirmed that at least one carbon-based radicalintermediate was formed during the direct photolysisof propranolol in aqueous solutions. The overall resultsdemonstrated that with fast direct photolysis half-lives, propranolol is unlikely to be persistent in naturalwaters. Further work is needed to investigate indirectphotolysis of atenolol and metoprolol in surface waters inorder to understand the overall persistence of theseAPIs in the environment.
-blockers: propranolol (hydrochloride salt), atenolol,and metoprolol (succinate salt) were investigated by exposingthe samples (0.0003-10 mg L-1) to a solar irradiator(filtered xenon lamp: 290-800 nm) at 20-26 C. Resultssuggested that direct photolysis in optically dilute solutionsfollowed pseudo first-order kinetics. The measured half-lives of propranolol, atenolol, and metoprolol wereapproximately 16, 350, and 630 h, respectively. Thesewere 3-5 orders of magnitude slower than the estimatedminimum half-lives. The measured half-lives were relatedto day light surface conditions by comparing the light intensityof the lamp and the sun at different latitudes and seasons.Major direct photolysis products were identified frompropranolol that led to a proposed reaction pathway, involvingring oxidation, rearrangement, and deoxygenation.Electron paramagnetic resonance (EPR) spectroscopyresults confirmed that at least one carbon-based radicalintermediate was formed during the direct photolysisof propranolol in aqueous solutions. The overall resultsdemonstrated that with fast direct photolysis half-lives, propranolol is unlikely to be persistent in naturalwaters. Further work is needed to investigate indirectphotolysis of atenolol and metoprolol in surface waters inorder to understand the overall persistence of theseAPIs in the environment.