Photophysical and photochemical properties of the pharmaceutical compound salbutamol in aqueous solutions

Occurrence and mass flows of contaminants of emerging concern (CECs) in Sweden's three largest lakes and associated rivers

Contaminants of emerging concern (CECs) are a concern in aquatic environments due to possible adverse effects on the environment and humans. This study assessed the occurrence and mass flows of CECs in Sweden's three largest lakes and 24 associated rivers. The occurrence and distribution of 105 CECs was investigated, comprising 71 pharmaceuticals, 13 perfluoroalkyl substances (PFASs), eight industrial chemicals, four personal care products (PCPs), three parabens, two pesticides, and four other CECs (mostly anthropogenic markers). This is the first systematic study of CECs in Sweden's main lakes and one of the first to report environmental concentrations of the industrial chemicals tributyl citrate acetate and 2,2'-dimorpholinyldiethyl-ether. The ∑CEC concentration was generally higher in river water (31-5200 ng/L; median 440 ng/L) than in lake water (36-900 ng/L; median 190 ng/L). At urban lake sites, seasonal variations were observed for PCPs and parabens, and also for antihistamines, antidiabetics, antineoplastic agents, antibiotics, and fungicides. The median mass CEC load in river water was 180 g/day (range 4.0-4300 g/day), with a total mass load of 5000 g/day to Lake Vänern, 510 g/day to Lake Vättern, and 5600 g/day to Lake Mälaren. All three lakes are used as drinking water reservoirs, so further investigations of the impact of CECs on the ecosystem and human health are needed.

Direct and nitrite-sensitized indirect photolysis of effluent-derived phenolic contaminants under UV254 irradiation

UV₂₅₄ photolysis has increasingly been utilized for disinfection of water-born pathogens in wastewater. During disinfection, wastewater-derived trace organic contaminants, such as pharmaceuticals and personal care products (PPCPs), may be subjected to direct photolysis and indirect photolysis sensitized by wastewater constituents such as nitrite (NO₂^-). Herein, we reported the direct photolysis and NO₂^--sensitized indirect photolysis of four phenolic contaminants commonly observed in wastewaters (i.e., bisphenol A (BPA), acetaminophen (ATP), salbutamol (SAL), and 2,4-dihydroxybenzophenone (BP1)). Spectroscopic characterization and quantum yield measurement were carried out to evaluate the photochemical reactivity of these phenolic compounds. In NO₂^--sensitized photolysis, the relative contribution of direct and indirect photolysis was quantified by light screening factor calculation and radical quenching studies. The experimental results highlight the important roles of HO˙ and NO₂˙ in the NO₂^--sensitized photolysis of phenolic compounds. A series of intermediate products, including hydroxylated, nitrated, nitrosated, dimerized, and alkyl chain cleavage products, were identified by solid phase extraction (SPE) combined with high-resolution mass spectrometry (HRMS) analyses. On the basis of identified products, the underlying mechanisms and transformation pathways for NO₂^--sensitized photolysis of these phenolic compounds were elucidated. The second-order rate constants of BPA, SAL, BP1 with NO₂˙ were calculated to be 2.25 × 10⁴, 1.35 × 10⁴ and 2.44 × 10⁴ M^-1 s^-1, respectively, by kinetic modeling. Suwanee River natural organic matter (SRNOM) played complex roles in the direct and NO₂^--sensitized photolysis of phenolic compounds by serving as a photosensitizer, light screening and radical quenching agent. Wastewater constituents, such as NO₃^- and EfOM, could accelerate direct and NO₂^--sensitized photolysis of BPA, SAL, and BP1 in the wastewater matrix. Our results suggest that NO₂^- at the WWTP effluent-relevant level can sensitize the photolysis of effluent-derived phenolic contaminants during the UV₂₅₄ disinfection process; however, the formation of potentially carcinogenic and mutagenic nitrated/nitrosated derivatives should be scrutinized.

Photochemical study of the highly used corticosteroids dexamethasone and prednisone. Effects of micellar confinement and cytotoxicity analysis of photoproducts

Photodegradation of dexamethasone (Dexa) and prednisone (Pred) occurs by a combination of ROS attack and unimolecular photodegradation reactions. The photoproducts obtained are more cytotoxic than the parent compounds.

Contrasting photoreactivity of β2-adrenoceptor agonists Salbutamol and Terbutaline in the presence of humic substances

The photodegradation reactions of two typical β2-adrenoceptor agonists, salbutamol (SAL) and terbutaline (TBL), alone, and in the presence of Aldrich humic acid (AHA) or Suwannee River fulvic acid (SRFA) were investigated by steady-state photolysis experiments, laser flash photolysis (LFP), kinetic modeling and quantum calculation. AHA and SRFA (2-20 mgC L^-1) accelerated the phototransformation of both SAL and TBL. For SAL, an inhibiting effect of oxygen on the photodegradation was observed that is fully consistent with the main involvement of excited triplet states of HS (³HS*). On the contrary, oxygen drastically enhanced the photodegradation of TBL showing that ³HS* were negligibly involved in the reaction. The involvement of singlet oxygen was also ruled out because of the low reaction rate constant measured between TBL and singlet oxygen. Quantum calculations were therefore performed to explore whether oxygenated radicals could through addition reactions explain the differences of reactivity of TBL and SAL in oxygen medium. Interestingly, calculations showed that in the presence of oxygen, the addition of phenoxyl on TBL led to the formation of adducts and to the loss of TBL while the same addition reaction on SAL partly regenerated the starting compound and at the end degraded SAL less efficiently. This study is of high relevance to understand the processes involved in SAL and TBL phototransformation and the photoreactivity of HS. Moreover, our findings suggest that TBL might be a promising probe molecule to delineate the role of oxygenated radicals.

Aquatic photolysis of β2-agonist salbutamol: kinetics and mechanism studies

Salbutamol (SAL) has been widely used as medicine both in treating asthma and in animal primary production; an increasing number of reports have detected SAL in natural waters. The photolysis kinetic and pathway of SAL in aquatic system were studied, as well as the effect of several natural water constituents, such as nitrate, dissolved oxygen (DO) and ferric ions. According to our research, the direct photolysis of SAL followed pseudo-first-order reaction kinetics. Alkaline condition could promote the degradation of SAL; the increase of solution pH would simultaneously increase the fraction of the deprotonated forms of SAL (including the deprotonated and zwitterionic species), which were easier to be excited, and result in the bathochromic shift of the UV-Vis spectrum and, finally, accelerate the degradation rate of SAL. The presence of nitrate could enhance the removal rate of SAL via generation hydroxyl radical (·OH) under irradiation. In addition, the absence of oxygen in the reaction solution could decrease the photolysis. Moreover, Fe(III) was able to chelate with SAL to form an octahedral complex, which was photochemically reactive. The octahedral complex could generate ·OH to oxidize SAL itself in turn. The pathways of SAL photolysis were also investigated by means of the solid phase extraction (SPE)-LC-MS method. The major pathways of SAL photodegradation included oxidation and side-chain cleavage.

Input of pharmaceuticals through coastal surface watercourses into a Mediterranean lagoon (Mar Menor, SE Spain): sources and seasonal variations

The seasonal occurrence and distribution of 69 pharmaceuticals along coastal watercourses during 6 sampling campaigns and their input through El Albujón watercourse to the Mar Menor lagoon were determined by UPLC-MS-MS, considering a total of 115 water samples. The major source of pharmaceuticals running into this watercourse was an effluent from the Los Alcazares WWTP, although other sources were also present (runoffs, excess water from irrigation, etc.). In this urban and agriculturally influenced watercourse different pharmaceutical distribution profiles were detected according to their attenuation, which depended on physicochemical water conditions, pollutant input variation, biodegradation and photodegradation rates of pollutants, etc. The less recalcitrant compounds in this study (macrolides, β-blockers, etc.) showed a relevant seasonal variability as a consequence of dissipation processes (degradation, sorption, etc.). Attenuation was lower, however, for diclofenac, carbamazepine, lorazepam, valsartan, sulfamethoxazole among others, due to their known lower degradability and sorption onto particulate matter, according to previous studies. The maximum concentrations detected were higher than 1000 ng L(-1) for azithromycin, clarithromycin, valsartan, acetaminophen and ibuprofen. These high concentration levels were favored by the limited dilution in this low flow system, and consequently some of them could pose an acute risk to the biota of this watercourse. Considering data from 2009 to 2010, it has been estimated that a total of 11.3 kg of pharmaceuticals access the Mar Menor lagoon annually through the El Albujón watercourse. The highest proportion of this input corresponded to antibiotics (46%), followed by antihypertensives (20%) and diuretics (18%).

A critical assessment of the photodegradation of pharmaceuticals in aquatic environments: defining our current understanding and identifying knowledge gaps

This work presents a critical assessment of the state and quality of knowledge around the aquatic photochemistry of human- and veterinary-use pharmaceuticals from laboratory experiments and field observations. A standardized scoring rubric was used to assess relevant studies within four categories: experimental design, laboratory-based direct and indirect photolysis, and field/solar photolysis. Specific metrics for each category are defined to evaluate various aspects of experimental design (e.g., higher scores are given for more appropriate characterization of light source wavelength distribution). This weight of evidence-style approach allowed for identification of knowledge strengths and gaps covering three areas: first, the general extent of photochemical data for specific pharmaceuticals and classes; second, the overall quality of existing data (i.e., strong versus weak); and finally, trends in the photochemistry research around these specific compounds, e.g. the observation of specific and consistent oversights in experimental design. In general, those drugs that were most studied also had relatively good quality data. The four pharmaceuticals studied experimentally at least ten times in the literature had average total scores (lab and field combined) of ≥29, considered decent quality; carbamazepine (13 studies; average score of 31), diclofenac (12 studies; average score of 31), sulfamethoxazole (11 studies; average score of 34), and propranolol (11 studies; average score of 29). Major oversights and errors in data reporting and/or experimental design included: lack of measurement and reporting of incident light source intensity, lack of appropriate controls, use of organic co-solvents in irradiation solutions, and failure to consider solution pH. Consequently, a number of these experimental parameters were likely a cause of inconsistent measurements of direct photolysis rate constants and quantum yields, two photochemical properties that were highly variable in the literature. Overall, the assessment rubric provides an objective and scientifically-defensible set of metrics for assessing the quality of a study. A major recommendation is the development of a method guideline, based on this rubric, for conducting and reporting on photochemical studies that would produce consistent and reliable data for quantitative comparison across studies. Furthermore, an emphasis should be placed on conducting more dual-fate studies involving controlled photolysis experiments in natural sunlight, and whole system fate studies in either natural or artificial systems. This would provide accurate data describing the actual contribution of photolysis to the overall fate of pharmaceuticals in the environment.

Determination of salbutamol by direct chiral reversed-phase HPLC using teicoplanin as stationary phase and its application to natural water analysis

A direct chiral LC-UV method was optimized for the determination of salbutamol (SAL) β2 -agonist in environmental water. Two commercially available columns were evaluated: teicoplanin Chirobiotic-T™ (150 × 2.1 mm i.d., 5 µm) and vancomycin Chirobiotic-V™ (150 × 2.1 mm i.d., 5 µm). Finally, teicoplanin chiral stationary phase was selected for SAL enantiomer resolution. In order to preserve its integrity and maintain the column performance for longer time, the use of additives such as triethylamine (TEA) in the mobile phase was avoided. Experimental design was applied to simultaneously evaluate the influence of several parameters involved in enantiomer separation and to establish the conditions for acceptable resolution and performance in short analysis time. Optimum mobile phase was methanol-20 mM ammonium acetate buffer at pH 4.5 (98:2, v/v). A solid-phase extraction procedure for sample pre-concentration and clean-up allowed the determination of chiral SAL residues in natural water samples spiked at low concentrations in the range 1.0-20 ng mL(-1) . Reproducible recoveries, between 77 and 98%, were obtained and matrix effect was negligible. Injection of sample solutions at low elution strength permitted the SAL enantioresolution in the natural water complex matrix with satisfactory sensitivity and precision.