Major Transformation Products Research Articles

Photocatalytic degradation kinetics, mechanism and ecotoxicity assessment of tramadol metabolites in aqueous TiO2 suspensions

This study investigated for the first time the photocatalytic degradation of three well-known transformation products (TPs) of pharmaceutical Tramadol, N-desmethyl-(N-DES), N,N-bidesmethyl (N,N-Bi-DES) and N-oxide-tramadol (N-OX-TRA) in two different aquatic matrices, ultrapure water and secondary treated wastewater, with high (10mgL−1) and low (50μgL−1) initial concentrations, respectively. Total disappearance of the parent compounds was attained in all experiments. For initial concentration of 10mgL−1, the target compounds were degraded within 30–40min and a mineralization degree of more than 80% was achieved after 240min of irradiation, while the contained organic nitrogen was released mainly as NH4+ for N-DES, N,N-Bi-DES and NO3− for N-OX-TRA. The degradation rates of all the studied compounds were considerably decreased in the wastewater due to the presence of inorganic and organic constituents typically found in effluents and environmental matrices which may act as scavengers of the HO•. The effect of pH (4, 6.7, 10) in the degradation rates was studied and for N-DES-TRA and N,N-Bi-DES-TRA, the optimum pH value was 6.7. In contrast, N-OX-TRA showed an increasing trend in the photocatalytic degradation kinetic in alkaline solutions (pH 10). The major transformation products were identified by high resolution accurate mass spectrometry coupled with liquid chromatography (HR-LC–MS). Scavenging experiments indicated for all studied compounds the important role of HO• in the photocatalytic degradation pathways that included mainly hydroxylation and further oxidation of the parent compounds. In addition, Microtox bioassay (Vibrio fischeri) was employed for evaluating the ecotoxicity of photocatalytically treated solutions. Results clearly demonstrate the progressive decrease of the toxicity and the efficiency of the photocatalytic process in the detoxification of the irradiated solutions.

Thermal Losses of Tertiary Butylhydroquinone (TBHQ) and Its Effect on the Qualities of Palm Oil.

The rules and patterns of thermal losses of tertiary butylhydroquinone (TBHQ) in palm oil (PO) and its effect on the qualities of PO were investigated by oven heating method. Volatilization and transformation products of TBHQ in PO were also studied in detail under heating treatment. Results showed that at low temperature (< 135°C), TBHQ had better antioxidative properties, while its antioxidative potency to PO was significantly weakened at high temperature (≥ 135°C). In addition, as heating temperatures increased and heating time prolonged, losses of TBHQ significantly increased in PO. Volatilization was the major pathway for losses of TBHQ in PO under heating treatment. Meanwhile, a small portion of TBHQ was transformed and the major transformation product was 2-tertbutyl-1,4- benzoquinone (TQ). Moreover, TQ and several decomposition products of PO were also observed in the volatilization products of TBHQ.

물억새를 식재한 플러그 흐름 습지에서의 RDX 제거동역학

RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) is the most important explosive contaminant, both in concentration and in frequency, at military shooting ranges in which green technologies such as phytoremediation or constructed wetlands are the best option for mitigation of explosive compounds discharge to the environment. A study was conducted with two identical lab-scale plug flow constructed wetlands planted with Amur silver grass to treat water artificially contaminated with 40 mg/L of toxic explosive compound, RDX. The reactor was inoculated with or without RDX degrading mixed culture to evaluate plant-microorganism interactions in RDX removal, transformation products distribution, and kinetic constants. RDX and its metabolites in water, plant, and sediment were analyzed by HPLC to determine mass balance and kinetic constants. After 30 days of operation, the reactor reached steady-state at which more than 99% of RDX was removed with or without the mixed culture inoculation. The major transformation product was TNX (Trinitroso-RDX) that comprised approximately 50% in the mass balance of both reactors. It was also the major compound in the plant root and shoot system. Acute toxicity analysis of the water samples showed more than 30% of toxicity reduction in the effluent than that of influent containing 40 mg/L of RDX. In the Amur silver grass mesocosm seeded with the mixed culture, the specific RDX removal rate, that is 1st order removal rate normalized to plant fresh weight, was estimated to be 0.84 kg^&#x2212;1 day^&#x2212;1 which is 16.7% higher than that in the planted only mesocosm. Therefore, the results of this study proved that Amur silver grass is an effective plant for RDX removal in constructed wetlands and the efficiency can be increased even more when applied with RDX degrading microbial consortia.

Sorption, uptake, and biotransformation of 17β-estradiol, 17α-ethinylestradiol, zeranol, and trenbolone acetate by hybrid poplar.

Hormonally active compounds may move with agricultural runoff from fields with applied manure and biosolids into surface waters where they pose a threat to human and environmental health. Riparian zone plants could remove hormonally active compounds from agricultural runoff. Therefore, sorption to roots, uptake, translocation, and transformation of 3 estrogens (17β-estradiol, 17α-ethinylestradiol, and zeranol) and 1 androgen (trenbolone acetate) commonly found in animal manure or biosolids were assessed by hydroponically grown hybrid poplar, Populus deltoides x nigra, DN-34, widely used in riparian buffer strips. Results clearly showed that these hormones were rapidly removed from 2 mg L(-1) hydroponic solutions by more than 97% after 10 d of exposure to full poplar plants or live excised poplars (cut-stem, no leaves). Removals by sorption to dead poplar roots that had been autoclaved were significantly less, 71% to 84%. Major transformation products (estrone and estriol for estradiol; zearalanone for zeranol; and 17β-trenbolone from trenbolone acetate) were detected in the root tissues of all 3 poplar treatments. Root concentrations of metabolites peaked after 1 d to 5 d and then decreased in full and live excised poplars by further transformation. Metabolite concentrations were less in dead poplar treatments and only slowly increased without further transformation. Taken together, these findings show that poplars may be effective in controlling the movement of hormonally active compounds from agricultural fields and avoiding runoff to streams.

Suspect screening of emerging pollutants and their major transformation products in wastewaters treated with fungi by liquid chromatography coupled to a high resolution mass spectrometry

A new approach for the screening of 33 pharmaceuticals and 113 of their known transformation products in wastewaters was developed. The methodology is based on the analysis of samples by liquid chromatography coupled to high resolution mass spectrometry (HRMS) followed by data processing using specific software and manual confirmation. A home-made library was built with the transformation products reported in literature for the target pharmaceuticals after treatment with various fungi. The method was applied to the search of these contaminants in 67 samples generated along treatment of wastewaters with white-rot fungus Trametes versicolor. The screening methodology allowed the detection of different transformation products (TPs) generated from degradation of parent compounds after fungal treatment. This approach can be a useful tool for the rapid screening and tentative detection of emerging contaminants during water treatment in both full and batch-scale studies when pure standards are not available.

Aerobic biotransformation studies of two trifluoromethoxy-substituted aliphatic alcohols and a novel fluorinated C3-based building block

Abstract Fluorinated substances play a significant role for many industrial and consumer products, but many of these chemicals are attributed with an adverse ecological profile and persistence in the environment. Herein, three potentially more environmentally benign substitutes were assessed for aerobic biotransformation, namely 3-(trifluoromethoxy)-propan-1-ol (TFMPrOH), 6-(trifluoromethoxy)-hexan-1-ol (TFMHxOH) and 1-(2,2,3,3,4,4,4-heptafluorobutoxy)-propan-2-ol (HFBPrOH). Analytical techniques involved different HPLC–ESI-MS/MS techniques as well as determination of fluoride in order to assess the extent of mineralization. The two trifluoromethoxy-substituted alcohols showed very different results concerning mineralization. Whereas TFMPrOH only yielded approximately 15% fluoride, TFMHxOH reached nearly quantitative release of fluoride after 37 days. The latter one yielded 6-trifluoromethoxy hexanoic acid (TFMHxA) as well as trifluoromethyl carbonate (TFMC) as transient transformation products, both of which were entirely degraded. TFMC was also detected during biotransformation of TFMPrOH, however, the major transformation product was 3-trifluoromethoxy-propanoic acid (TFMPrA), which did not show any further degradation within a 47 days period. The third compound under investigation, HFBPrOH, expectedly yielded perfluorobutanoic acid as a stable biotransformation product. Several acidic biotransformation intermediates as well as heptafluorobutan-1-ol were identified and a biotransformation pathway was postulated. TFMHxOH might therefore be incorporated into fluorinated substances, for instance by ester linkages assuming that biotransformation of such substances would yield the alcohol.

Identification of transformation products of rosuvastatin in water during ZnO photocatalytic degradation through the use of associated LC–QTOF–MS to computational chemistry

Rosuvastatin (RST), a synthetic statin, is a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, with a number of pleiotropic properties, such as anti-inflammation, antioxidation and cardiac remodelling attenuation. According to IMS Health, rosuvastatin was the third best-selling drug in the United States in 2012. RST was recently found in European effluent samples at a detection frequency of 36%. In this study, we evaluate the identification process of major transformation products (TPs) of RST generated during the heterogeneous photocatalysis process with ZnO. The degradation of the parent molecule and the identification of the main TPs were studied in demineralised water. The TPs were monitored and identified by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC–QTOF–MS/MS). Ten TPs were tentatively identified and some of them originated from the hydroxylation suffered by the aromatic ring during the initial stages of the process. Structural elucidation of some of the most abundant or persistent TPs was evaluated by computational analysis, which demonstrated that this approach can be used as a tool to help the elucidation of structures of unknown molecules. The analysis of the parameters obtained from ab initio calculations for different isomers showed the most stable structures and, consequently, the most likely to be found.

Identification of 4-Hydroxycumyl Alcohol As the Major MnO2-Mediated Bisphenol A Transformation Product and Evaluation of Its Environmental Fate.

Bisphenol A (BPA), an environmental contaminant with weak estrogenic activity, resists microbial degradation under anoxic conditions but is susceptible to abiotic transformation by manganese dioxide (MnO2). BPA degradation followed pseudo-first-order kinetics with a rate constant of 0.96 (±0.03) min(-1) in the presence of 2 mM MnO2 (0.017% w/w) at pH 7.2. 4-hydroxycumyl alcohol (HCA) was the major transformation product, and, on a molar basis, up to 64% of the initial amount of BPA was recovered as HCA. MnO2 was also reactive toward HCA, albeit at 5-fold lower rates, and CO2 evolution (i.e., mineralization) occurred. In microcosms established with freshwater sediment, HCA was rapidly biodegraded under oxic, but not anoxic conditions. With a measured octanol-water partition coefficient (Log K(ow)) of 0.76 and an aqueous solubility of 2.65 g L(-1), HCA is more mobile in saturated media than BPA (Log K(ow) = 2.76; aqueous solubility = 0.31 g L(-1)), and therefore more likely to encounter oxic zones and undergo aerobic biodegradation. These findings corroborate that BPA is not inert under anoxic conditions and suggest that MnO2-mediated coupled abiotic-biotic processes may be relevant for controlling the fate and longevity of BPA in sediments and aquifers.

Photodegradation of single and mixture of parabens – Kinetic, by-products identification and cost-efficiency analysis

Esters of p-hydroxybenzoic acid, commonly known as parabens are preservatives used in a variety of personal care products, cosmetics, pharmaceutical and food products.This paper presents the results of studies on photochemical degradation of hazardous water contaminants – methyl- (MP), ethyl- (EP), propyl- (PP), butyl- (BuP), benzylparaben (BeP) and p-hydroxybenzoic acid (p-HBA) (individually or in mixture) using ultraviolet C lamps in the presence and absence of hydrogen peroxide. Both systems were very efficient on the degradation of the single parent compounds. Total removal of individual pollutant was achieved after 2h or 6min for UVC and UVC/H2O2, respectively. The kinetic constants of hydroxyl radicals reaction and the photolysis quantum yields were obtained for each pollutant. The decomposition of the mixture of the six compounds with the H2O2/UVC system ensures a complete degradation after 30min with a degree of mineralization of 25%. Whereas only 10% of mineralization was observed after the same time for photolysis. The pseudo-first-order fluence-based rate constants (for UVC and H2O2/UVC) for each paraben in the mixture reaction were calculated for the first time. The analysis using UHPLC/MS/MS technique shows that hydroxylation is the main pathway of the reaction with hydroxyl radicals. In fact, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid and 3,4-dihydroxybenzoic acid were identified as a major transformation products. Moreover the mono, di and tri derivatives of parabens were detected as the main intermediates formed during oxidation. The fluence-based experimental data and cost analysis showed that the H2O2/UVC treatment was effective in mineralizing of the parabens mixture.

Photocatalytic and photoelectrocatalytic degradation of the drug omeprazole on nanocrystalline titania films in alkaline media: Effect of applied electrical bias on degradation and transformation products

Photocatalytic and photoelectrocatalytic degradation of the drug omeprazole has been studied in the presence of nanocrystalline titania films supported on glass slides or transparent FTO electrodes in alkaline environment. Its photocatalytic degradation rate was assessed by its UV absorbance and by HPLC, while its transformation products were analyzed by HR-LC–MS. Based on UV absorbance, omeprazole can be photocatalytically degraded at an average rate of 6.7×10−4min−1 under low intensity UVA irradiation of 1.5mWcm−2 in the presence of a nanoparticulate titania film. This corresponds to degradation of 1.4mg of omeprazole per gram of the photocatalyst per liter of solution per hour. The photodegradation rate can be accelerated in a photoelectrochemical cell by applying a forward bias. In this case, the maximum rate reached under the present conditions was 11.6×10−4min−1 by applying a forward bias of +0.6V vs. Ag/AgCl. Four major transformation products were successfully identified and their profiles were followed by HR-LC–MS. The major degradation path includes the scission of the sulfoxide bridge into the corresponding pyridine and benzimidazole ring derivates and this is accompanied by the release of sulfate anions in the reaction mixture.

Occurrence of bisphenol A in surface and drinking waters and its physicochemical removal technologies

Bisphenol A (BPA), an endocrine disrupting compound, has caused wide public concerns due to its wide occurrence in environment and harmful effects. BPA has been detected in many surface waters and drinking water with the maximum concentrations up to tens of μg·L−1. The physicochemical technology options in eliminating BPA can be divided into four categories: oxidation, advanced oxidation, adsorption and membrane filtration. Each removal option has its own limitation and merits in removing BPA. Oxidation and advanced oxidation generally can remove BPA efficiently while they also have some drawbacks, such as high cost, the generation of a variety of transformation products that are even more toxic than the parent compound and difficult to be mineralized. Only few advanced oxidation methods have been reported to be able to mineralize BPA completely. Therefore, it is important not only to identify the major initial transformation products but also to assess their estrogenic activity relative to the parent compounds when oxidation methods are employed to remove BPA. Without formation of harmful by-products, physical separation methods such as activated carbon adsorption and membrane processes are able to remove BPA in water effluents and thus have potential as BPA removal technologies. However, the necessary regeneration of activated carbon and the low BPA removal efficiency when the membrane became saturated may limit the application of activated carbon adsorption and membrane processes for BPA removal. Hybrid processes, e.g. combining adsorption and biologic process or combining membrane and oxidation process, which can achieve simultaneous physical separation and degradation of BPA, will be highly preferred in future.

Impact of sulfidation on the bioavailability and toxicity of silver nanoparticles to Caenorhabditis elegans

Sulfidation is a major transformation product for manufactured silver nanoparticles (Ag-MNPs) in the wastewater treatment process. We studied the dissolution, uptake, and toxicity of Ag-MNP and sulfidized Ag-MNPs (sAg-MNPs) to a model soil organism, Caenorhabditis elegans. Our results show that reproduction was the most sensitive endpoint tested for both Ag-MNPs and sAg-MNPs. We also demonstrate that sulfidation not only decreases solubility of Ag-MNP, but also reduces the bioavailability of intact sAg-MNP. The relative contribution of released Ag+ compared to intact particles to toxicity was concentration dependent. At lower total Ag concentration, a greater proportion of the toxicity could be explained by dissolved Ag, whereas at higher total Ag concentration, the toxicity appeared to be dominated by particle specific effects.

Degradation of chiral neonicotinoid insecticide cycloxaprid in flooded and anoxic soil

Cycloxaprid (CYC), with two stereogenic centers from oxabridged ring, is a novel potent neonicotinoid insecticide. The investigation of relevant transformation products (TPs) is critical for the risk evaluation of CYC on environment impact and further regulatory decisions. In this study, stereoselective soil metabolism of CYC enantiomers was investigated using isotope labeling techniques. Liquid scintillation counting with LC–MS/MS was used to identify and quantify the major transformation products (TPs) of CYC enantiomers in four various soils under anoxic and flooded condition. Most of CYC had been transformed in four soils at 5d after treatment. Furthermore, CYC was found converted to a range of transformation products, which exhibited soil-specific dynamic changes. Cleavage of the oxabridged seven-member ring, reductive dechlorination in the chloropyridinyl and cleavage of C–N between the chloropyridinylmethyl and imidazalidine ring are the main transformation pathways of CYC. It is presumed that acidic condition may conduce to form the cleavage product of oxabridged seven-member ring. However, abiotic or biotic stereoselective persistence of TPs in all soils was not observed from the experimental data and may be attributed to the unstable oxabridged ring.

Identification and monitoring of thiabendazole transformation products in water during Fenton degradation by LC-QTOF-MS.

This work enabled the identification of major transformation products (TPs) of thiabendazole (TBZ) during the Fenton process. TBZ is a benzimidazole fungicide widely used around the world to prevent and/or treat a wide range of fruit and vegetable pathogens. The degradation of the parent molecule and the identification of the main TPs were carried out in demineralized water. The TPs were monitored and identified by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS). Up to 12 TPs were tentatively identified. Most of them were eliminated after 15min of treatment time and originated from numerous hydroxylations undergone by the aromatic ring during the initial stages of the process.

Aqueous phototransformation of bisphenol S: the competitive radical-attack pathway to p-hydroxybenzenesulfonic acid.

The kinetics, environmental influencing factors, products and reaction mechanism of aqueous phototransformation of bisphenol S (BPS), as an alternative to bisphenol A, which is of environmental concern, were investigated. p-Hydroxybenzenesulfonic acid, as the major transformation product was confirmed by gas chromatography - mass spectrometry, electrospray ionization, ¹H nuclear magnetic resonance and fluorescence spectrum analysis. A reaction pathway was proposed based on the reactive oxygen species related results by electron paramagnetic resonance and radical traps. The competition of the excited state of BPS between transferring electron to O₂ to •O₂(-) and directly oxidizing H₂O to •OH was revealed.

Targeted Petroleomics: Analytical Investigation of Macondo Well Oil Oxidation Products from Pensacola Beach

Of the estimated 5 million barrels of crude oil released into the Gulf of Mexico from the Deepwater Horizon oil spill, a fraction washed ashore onto sandy beaches from Louisiana to the Florida panhandle. Here, we compare the detailed molecular analysis of hydrocarbons in oiled sands from Pensacola Beach to the Macondo wellhead oil (MWO) by electrospray (ESI) and atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to identify major environmental transformation products of polar, high molecular weight (C>25) “heavy ends” (high-boiling species) inaccessible by gas chromatography. The petrogenic material isolated from the Pensacola Beach sand displays greater than 2-fold higher molecular complexity than the MWO constituents, most notably in oxygenated species absent in the parent MWO. Surprisingly, the diverse oxygenated hydrocarbons in the Pensacola Beach sediment extracts were dominant in all ionization modes investigated, (±) ESI and (±) APPI....

Enhanced non-extractable residue formation of 14C-metalaxyl catalyzed by an immobilized laccase

We studied the influence of an immobilized laccase from Trametes versicolor on non-extractable residue (NER) formation of the systemic fungicide 14C-metalaxyl in soil. We added the enzyme (130 mU/g DW) to soil sterilized by gamma irradiation and observed that the amount of NER (6.3 % of applied radioactivity) after 10 days of incubation was enhanced about twofold compared to the sterile soil without laccase addition. Residues formed within samples without enhanced enzyme activity were mainly bound via ester linkages to all fractions of humic matter, i.e., fulvic acids, humic acids, non-humines, and humines, respectively. In contrast, residues formed in presence of immobilized laccase were more strongly bound by covalent linkages such as ether and C-C bonds, especially to humic acids. After chemical degradation of the humic matter, it could be observed that all NER contained the first major transformation product, i.e., metalaxyl acid. The findings underline that the residue formation of metalaxyl in soil may be partly catalyzed by immobilized extracellular oxidative enzymes through oxidative coupling reactions within the humic matter.

TiO2 photocatalysis of 2-isopropyl-3-methoxy pyrazine taste and odor compound in aqueous phase: Kinetics, degradation pathways and toxicity evaluation

In recognition of the growing demand regarding the control of undesired taste and odor (T&O) problems in natural water resources, the photocatalytic degradation of 2-isopropyl-3 methoxy pyrazine (IPMP), a common metabolite of soil actinomycetes which contributes a rotten vegetable odor to water, was investigated under simulated solar irradiation. Under the studied conditions (C=10mgL−1, CTiO2=100 mg L−1 and I=600Wm−2), 95% of IPMP was removed within 20min of irradiation. The reaction intermediates were completely mineralized to CO2 and the nitrogen was predominantly released as NH4+ ions after 240min irradiation. The major transformation products of TiO2 photocatalysis of IPMP have been determined by the use of high resolution accurate liquid chromatography–orbitrap mass spectrometry as well as gas chromatography–mass spectrometry (GC–MS) techniques. Hydroxylation of the isopropyl and methoxy groups has been identified as the main reaction pathway. Scavenging experiments indicated the important role of HO•, h+ and O2•− in the photocatalytic process. Toxicity assessment revealed the efficiency of the photocatalytic treatment to achieve almost complete detoxification of the irradiated solution.

Biotransformation of Benzotriazoles: Insights from Transformation Product Identification and Compound-Specific Isotope Analysis

Benzotriazoles are widely used domestic and industrial corrosion inhibitors and have become omnipresent organic micropollutants in the aquatic environment. Here, the range of aerobic biological degradation mechanisms of benzotriazoles in activated sludge was investigated. Degradation pathways were elucidated by identifying transient and persistent transformation products in batch experiments using liquid chromatography-high-resolution tandem mass spectrometry (LC-HR-MS/MS). In addition, initial reactions were studied using compound-specific isotope analysis (CSIA). Biodegradation half-lives of 1.0 days for 1H-benzotriazole, 8.5 days for 4-methyl-1H-benzotriazole, and 0.9 days for 5-methyl-1H-benzotriazole with activated sludge confirmed their known partial persistence in conventional wastewater treatment. Major transformation products were identified as 4- and 5-hydroxy-1H-benzotriazole for the degradation of 1H-benzotriazole, and 1H-benzotriazole-5-carboxylic acid for the degradation of 5-methyl-1H-benzotriazole. These transformation products were found in wastewater effluents, showing their environmental relevance. Many other candidate transformation products, tentatively identified by interpretation of HR-MS/MS spectra, showed the broad range of possible reaction pathways including oxidation, alkylation, hydroxylation and indicate the significance of cometabolic processes for micropollutant degradation in biological wastewater treatment in general. The combination of evidence from product analysis with the significant carbon and nitrogen isotope fractionation suggests that aromatic monohydroxylation is the predominant step during the biotransformation of 1H-benzotriazole.

Degradation rate of sodium fluoroacetate in three New Zealand soils

The degradation rate of sodium fluoroacetate (SFA) was assessed in a laboratory microcosm study incorporating 3 New Zealand soil types under different temperature (5 °C, 10 °C, or 20 °C) and soil moisture (35% or 60% water holding capacity) conditions using guideline 307 from the Organisation for Economic Co-operation and Development. A combination of nonlabeled and radiolabeled (14) C-SFA was added to soil microcosms, with sampling and analysis protocols for soil, soil extracts, and evolved CO(2) established using liquid scintillation counting and liquid chromatography-mass spectrometry. Degradation products of SFA and their rates of formation were similar in the 3 soil types. The major degradation pathway for SFA was through microbial degradation to the hydroxyl metabolite, hydroxyacetic acid, and microbial mineralization to CO(2), which constituted the major transformation product. Temperature, rather than soil type or moisture content, was the dominant factor affecting the rate of degradation. Soil treatments incubated at 20 °C displayed a more rapid loss of (14)C-SFA residues than lower temperature treatments. The transformation half-life (DT50) of SFA in the 3 soils increased with decreasing temperature, varying from 6 d to 8 d at 20 °C, 10 d to 21 d at 10 °C, and 22 d to 43 d at 5 °C.