Kinetics and Degradation Products for Direct Photolysis of β-Blockers in Water

Abstract

Related to improving persistence assessment of active pharmaceutical ingredients (APIs), direct aqueous photolysis of beta-blockers: propranolol (hydrochloride salt), atenolol, and metoprolol (succinate salt) were investigated by exposing the samples (0.0003-10 mg L(-1)) to a solar irradiator (filtered xenon lamp: 290-800 nm) at 20-26 degrees C. Results suggested that direct photolysis in optically dilute solutions followed pseudo first-order kinetics. The measured half-lives of propranolol, atenolol, and metoprolol were approximately 16, 350, and 630 h, respectively. These were 3-5 orders of magnitude slower than the estimated minimum half-lives. The measured half-lives were related to day light surface conditions by comparing the light intensity of the lamp and the sun at different latitudes and seasons. Major direct photolysis products were identified from propranolol that led to a proposed reaction pathway, involving ring oxidation, rearrangement, and deoxygenation. Electron paramagnetic resonance (EPR) spectroscopy results confirmed that at least one carbon-based radical intermediate was formed during the direct photolysis of propranolol in aqueous solutions. The overall results demonstrated that with fast direct photolysis half-lives, propranolol is unlikely to be persistent in natural waters. Further work is needed to investigate indirect photolysis of atenolol and metoprolol in surface waters in order to understand the overall persistence of these APIs in the environment.

Contrasting mechanisms of metoprolol uptake on kaolinite and talc

“…In a hydrolytic stability test, MT was found stable under pH 4, 7, and 9, with an estimated haft-life of more than a year in aquatic environments at 25°C [28]. Laboratory measurements of direct photolysis of MT resulted in a t 1/2 of 630 and 990 h with initial MT concentrations of 1 and 10 mg/L [24]. No biodegradation was detected over a 50 pore-volume time span in a column transport experiment with an input MT concentration of 0.5 mg/L [41], nor in the nitrification enrichment culture [40].…”

Accounting for the dissociating properties of organic chemicals in LCIA: An uncertainty analysis applied to micropollutants in the assessment of freshwater ecotoxicity

“…In the present study, averwhere pKa is the negative logarithm (log10) of the dissociation constant, f is KOW,n/(KOW,n + 1), and fn is the fraction of neutral molecules according to the Henderson-Hasselbalch equation: 1 age full day direct photolyis rates for winter and summer seasons were calculated by GCSOLAR [20]. Experimental molar absorption coefficients in function of the UV/VIS wavelength range (εA, in l mol −1 cm −1 ) were gathered in the literature [19,[21][22][23][24][25][26][27][28] as well…”

Photocatalysis of β-blockers – An overview

“…The occurrence of b-blockers has been repeatedly reported in recent years in the effluents of many wastewater treatment plants around the world (Brun et al, 2006;Carlsson et al, 2009;Conkle et al, 2008;Gabet-Giraud et al, 2010;Huggett et al, 2003;Joakim Larsson and Fick, 2009;Liu and Williams, 2007;Nikolai et al, 2006;Sacher et al, 2001;Ternes, 1998). These compounds are persistent against biological degradation and natural attenuation, and therefore, may remain in the environment for a long time.…”