Toxicity Of Degradation Products Research Articles

Insight on magnetic nitrogen-doped graphene oxide composite electrode constructing heterogeneous Electro-Fenton system for treating organophosphorus pesticide wastewater

The treatment of organic phosphorus pesticide (OPP) wastewater faces challenges such as incomplete degradation and low reaction efficiency. While heterogeneous electro-Fenton (Hetero-EF) has emerged as the preferred technology for addressing these issues due to its high treatment efficiency, further optimization is still necessary. This study used a one-pot hydrothermal method to prepare magnetic nitrogen-doped graphene oxide (Fe3O4@N-GO) composite electrodes to construct a novel Hetero-EF system. Dimethoate (DIM) was chosen as the representative pollutant to investigate the effects of parameters such as current density, pH, electrode spacing, and loading amount on degradation efficiency. The results demonstrated complete degradation of DIM within 40 min. Density functional theory (DFT) calculations and intermediate product analysis revealed that the reactive sites for DIM degradation were the P=S and P=S bonds, involving both hydrolysis and •OH pathways, with a decrease in toxicity of degradation products observed. Compared to graphite electrodes, Fe3O4@N-GO composite electrodes significantly increased H2O2 production, achieving complete DIM degradation even after 5 cycles, with a phosphate conversion rate of 30–40 %. This study highlights the innovative strategy of the Hetero-EF system in its significant application value for OPP treatment.

Novel MOF-derived Fe/CoNHDC-400@GF cathode with improved in-situ catalytic degradation of chloroquine phosphate during heterogeneous electro-Fenton process

The preparation of stable and high-efficiency heterogeneous electro-Fenton cathodes for the treatment of pollutants is important for environmental remediation. Herein, a novel N-doped MOF-derived Fe/Co bimetallic catalyst was in-situ grown on graphite felt (GF) surface to yield a composite cathode Fe/CoNHDC-400@GF for use in electro-Fenton process. The introduction of cobalt accelerated electron transfer due to existing polyvalent metals. The synergistic effect between Co0, CoⅡ, CoШ, FeⅡ, and FeШ enabled the continuous generation of reactive oxygen species (•OH and •O2−). Under near-neutral conditions (pH=6.5), complete removal of 10mgL-1 chloroquine phosphate (CQP) was achieved within 60min. Additionally, efficient removal was also achievable over a wide pH range (pH=3-11). The mechanistic investigations indicated •OH as a major active oxygen species for CQP degradation. A combination of the experimental results with density functional theory calculations (DFT) clarified the degradation pathway and intermediate products of CQP. Moreover, the toxicity of degradation products significantly reduced. Overall, valuable insights on preparing composite cathodes grown in-situ for efficient removal of refractory pollutants from wastewater during the heterogeneous electro-Fenton process were provided, useful for future consideration.

The CoO-doped carbon nanotubes enhance electronic performance and effectively activate persulfate for the degradation of sulfafurazole

In recent studies, carbon nanotube (CNTs) materials and their composites have demonstrated remarkable catalytic activity in the activation of persulfate (PS), facilitating the efficient degradation of organic pollutants. In this study, a novel Co loaded carbon nanotubes (CoO@CNT) catalyst was prepared to promote PDS activation for the degradation of sulfafurazole (SIZ). Experimental results, the CNT as a carrier effectively reduces the leaching of cobalt ions and improves the electron transport capacity，whereas the introduced Co effectively activates the PDS, promoting the generation of highly reactive radicals to degrade SIZ. Under optimized conditions (a catalyst dose of 0.2 g/L, a PDS dose of 1 g/L and an initial pH = 9.0), the obtained CoO@CNT demonstrated favorable Fenton-like performance, reaching a degradation efficiency of 95.55% within 30 min. Furthermore, density functional theory (DFT) calculations demonstrate that the introduction of cobalt (Co) accelerates electron transfer, promoting the decomposition of PDS while facilitating the Co2+/Co3+ redox cycling. We further employed the environmental chemistry and risk assessment system (ECOSAR) to evaluate the ecological toxicity of intermediate products, revealing a significant reduction in ecological toxicity associated with this degradation process, thereby confirming its environmental harmlessness. Through batch experiments and studies, we gained a comprehensive understanding of the mechanism and influencing factors of CoO@CNT in the role of SIZ degradation, and provided robust support for evaluating the ecological toxicity of degradation products. This study provides a significant strategy for the development of efficient catalysts incorporating Co for the environmentally friendly degradation of organic pollutants.

Identification and Mechanistic Analysis of Toxic Degradation Products in the Advanced Oxidation Pathways of Fluoroquinolone Antibiotics.

The degradation of fluoroquinolones (FQs) via advanced oxidation processes (AOPs) is a promising avenue, yet the complete mineralization of certain FQ molecules remains elusive, raising concerns about the formation of toxic by-products. This study delineates five primary AOP degradation pathways for 16 commercially available FQ molecules, inferred from existing literature. Density functional theory (DFT) was employed to calculate the bond dissociation energies within these pathways to elucidate the correlation between bond strength and molecular architecture. Subsequently, Comparative Molecular Similarity Index Analysis (CoMSIA) models were constructed for various degradation reactions, including piperazine ring cleavage, defluorination, hydroxylation, and piperazine ring hydroxylation. Three-dimensional contour maps generated from these models provide a deeper understanding of the interplay between FQ molecular structure and bond dissociation energy. Furthermore, toxicity predictions for 16 FQ molecules and their advanced oxidation intermediates, conducted using VEGA 1.2.3 software, indicate that degradation products from pathways P2 and P5 pose a heightened health risk relative to their parent compounds. Furthermore, the application of the Multwfn program to compute the Fukui function for FQ molecules discerns the disparity in degradation propensities, highlighting that N atoms with higher f0 values can augment the likelihood of piperazine ring cleavage. HOMO-LUMO distribution diagrams further confirm that methoxy substitution at the 1-position leads to a dilution of HOMOs on the piperazine ring and an increased energy gap for free radical reactions, diminishing the reactivity with hydroxyl radicals. This study elucidates the pivotal role of structural characteristics in FQ antibiotics for their degradation efficiency within AOPs and unveils the underlying mechanisms of bond dissociation energy disparities. The toxicity parameter predictions for FQ molecules and their intermediates offer unique perspectives and theoretical underpinnings for mitigating the use of high-risk FQs and for devising targeted degradation strategies to circumvent the generation of toxic intermediates in AOPs through molecular structure optimization.

The acute toxicity of Novichok's degradation products using quantitative and qualitative toxicology in silico methods.

The emergence of Novichok agents, potent organophosphorus nerve agents, has spurred the demand for advanced analytical methods and toxicity assessments as a result of their involvement in high-profile incidents. This study focuses on the degradation products of Novichok agents, particularly their potential toxic effects on biological systems. Traditional in vivo methods for toxicity evaluation face ethical and practical constraints, prompting a shift toward in silico toxicology research. In this context, we conducted a comprehensive qualitative and quantitative analysis of acute oral toxicity (AOT) for Novichok degradation products, using various in silico methods, including TEST, CATMoS, ProTox-II, ADMETlab, ACD/Labs Percepta, and QSAR Toolbox. Adopting these methodologies aligns with the 3Rs principle, emphasising Replacement, Reduction, and Refinement in the realm of toxicological studies. Qualitative assessments with STopTox and admetSAR revealed toxic profiles for all degradation products, with predicted toxicophores highlighting structural features responsible for toxicity. Quantitative predictions yielded varied estimates of acute oral toxicity, with the most toxic degradation products being EOPAA, MOPGA, MOPAA, MPGA, EOPGA, and MPAA, respectively. Structural modifications common to all examined hydrolytic degradation products involve substituting the fluorine atom with a hydroxyl group, imparting consequential effects on toxicity. The need for sophisticated analytical techniques for identifying and quantifying Novichok degradation products is underscored due to their inherent reactivity. This study represents a crucial step in unravelling the complexities of Novichok toxicity, highlighting the ongoing need for research into its degradation processes to refine analytical methodologies and fortify readiness against potential threats.

Photocatalytic degradation of oxytetracycline using ZnO catalyst

AbstractIn the present study, the degradation of oxytetracycline (OTC) under ultraviolet (UV) light in the presence of ZnO catalyst was investigated, and optimum parameters for degradation efficiency were determined. Different pH values, ZnO dosages, reaction times, OTC concentrations, and UV lights were used in this study. The optimum conditions found were as follows: pH 4, ZnO 1 g L−1, reaction time 25 min, and OTC concentration 10 mg L−1. Degradation efficiency was 42.1%, 76%, 70.7%, and 61.7% for ZnO and photocatalytic (for UV‐A, UV‐B, and UV‐C) degradation at optimal conditions, respectively. The resulting products after the photocatalytic oxidation of OTC were determined in the study. To identify the toxicity of degradation products and OTC, the lowest LC 50 (50% lethal concentration) and EC 50 (50% effective concentration) values were found. The resulting ethanamine, 2‐(2,6‐dimethylphenoxy)‐N‐methyl‐ by‐products were observed to be more toxic than OTC. Furthermore, it was seen that isopropoxy carbamic acid, ethyl ester by‐products were formed, whose presence is environmentally risky for aquatic environments due to their low EC50 values.

Flavonoid-Labeled Biopolymer in the Structure of Lipid Membranes to Improve the Applicability of Antioxidant Nanovesicles.

Nanovesicles produced with lipids and polymers are promising devices for drug and bioactive delivery and are of great interest in pharmaceutical applications. These nanovesicles can be engineered for improvement in bioavailability, patient compliance or to provide modified release or enhanced delivery. However, their applicability strongly depends on the safety and low immunogenicity of the components. Despite this, the use of unsaturated lipids in nanovesicles, which degrade following oxidation processes during storage and especially during the proper routes of administration in the human body, may yield toxic degradation products. In this study, we used a biopolymer (chitosan) labeled with flavonoid (catechin) as a component over a lipid bilayer for micro- and nanovesicles and characterized the structure of these vesicles in oxidation media. The purpose of this was to evaluate the in situ effect of the antioxidant in three different vesicular systems of medium, low and high membrane curvature. Liposomes and giant vesicles were produced with the phospholipids DOPC and POPC, and crystalline cubic phase with monoolein/DOPC. Concentrations of chitosan-catechin (CHCa) were included in all the vesicles and they were challenged in oxidant media. The cytotoxicity analysis using the MTT assay (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) revealed that concentrations of CHCa below 6.67 µM are non-toxic to HeLa cells. The size and zeta potential of the liposomes evidenced the degradation of their structures, which was minimized by CHCa. Similarly, the membrane of the giant vesicle, which rapidly deteriorated in oxidative solution, was protected in the presence of CHCa. The production of a lipid/CHCa composite cubic phase revealed a specific cubic topology in small-angle X-ray scattering, which was preserved in strong oxidative media. This study demonstrates the specific physicochemical characteristics introduced in the vesicular systems related to the antioxidant CHCa biopolymer, representing a platform for the improvement of composite nanovesicle applicability.

Anchoring CoTiO3/TiO2 heterostructure on fiber network actuates flow-through Fenton-like oxidation: Electronic modulation and rapid pollutants degradation

Versatile catalytic oxidation filtration system, especially under low operating pressure conditions, is a frontier technology for organic wastewater purification. Herein, CoTiO3/TiO2 heterostructure was anchored on fiber network (CTO/TOF) to actuate flow-through peroxymonosulfate (PMS) based oxidation toward organics removal. The well-developed built-in electric field in CoTiO3/TiO2 heterostructure induced local charge redistribution, and promoted the targeted adsorption and activation of PMS, thereby facilitating the activation process. Meanwhile, the 3D network of CTO/TOF fully exposes active sites, providing an ideal platform for mass transfer and surface reactions. Above 91% for nimesulide degradation was maintained after 24 h of catalytic permeation under high permeate flux (300.7 L/m2·h), corresponding to ultrafast retention time (4.9 s). Practical application experiments demonstrated that CTO/TOF+PMS system had strong anti-interference capability under diverse conditions. Synergy of radical-nonradical mixed pathways for pollutant removal was verified by electron paramagnetic resonance spectra, quenching tests, and electrochemical measurements. The degradation intermediates and possible degradation pathways of nimesulide were also proposed. The toxicity assessments confirmed decreased toxicity of degradation products. This study is dedicated to designing high-performance filters and broadening Fenton-like oxidation in environmental remediation.

Toxicity of products of thermal oxidative degradation of nitrogen-containing building polymer materials

Introduction. In the event of fires in residential premises in which nitrogen-containing thermal insulation materials (foam rubber, polyisocyanurate foam) are used, the victims will be exposed to toxic thermal degradation products. Data on long-term disorders caused by intoxication by thermal degradation products of these materials could not be found in the available literature. The aim of the study was to assess the toxicity of the products of thermal oxidative degradation of nitrogen-containing thermal insulation materials, both in the early and long-term post-intoxication period. 
 Material and methods. Static inhalation intoxication of rats with products of thermooxidative destruction of polyfoam and polyisocyanurate foam (at a concentration of 0,8HLC50) was simulated. The concentration of carboxyhemoglobin in the blood of rats, indicators of vital functions were determined immediately before and on days 1, 7 and 28 after exposure. To assess learning disabilities in rats, a conditioned reflex of active avoidance by swimming was developed. To assess spatial memory in rats, the method of developing and reproducing the conditioned reflex of searching for food was used.
 Results and discussion. The intoxication of rats with products of thermooxidative destruction of the studied materials of moderate severity was simulated. Violations of the functions of the respiratory and cardiovascular system of rats in the early (7 days) and long-term (28 days) post-intoxication period were not detected. In the long-term (28 days) post-intoxication period, an increase in the duration of the latent period of active avoidance by swimming of rats was determined (compared with the control), an increase in the number of spatial memory errors in rats and the time of testing (compared with the control) was revealed.
 Limitation of the study. Limitations are due to the methodology of the research being conducted. A quantitative analysis of only some gaseous products of thermal oxidative destruction was perfomed.
 Conclusion. It was found that intoxication of rats with products of thermooxidative destruction of foam rubber and foam polyiysocyanurate (at a concentration of 0,8HLC50) led to impaired learning and spatial memory of rats in the long-term post-intoxication period.

Controlling chloroform content to a safe level in a pharmaceutical oral solution of chloral hydrate

Abstract Chloral hydrate is a halogenated hydrocarbon with sedative and hypnotic properties and has been used for its medicinal properties for many years. Its solubility and permeability determine it as a Biopharmaceutical Classification System class 1 compound, and as such is ideal to be pharmaceutically presented as an aqueous oral liquid presentation. Its primary route of degradation is by hydrolysis to form formic acid and chloroform and hence licensed pharmaceutical presentations require validated methods to analyse these degradants. The content of the toxic chloroform degradation product was determined via a head-space gas chromatograph with a flame ionisation detector, and its content was controlled to a safe pharmaceutically acceptable level. This can be achieved by solution pH optimisation in the oral solution, incorporating a buffering system to control the rate of this degradation mechanism. Where other behavioural and pharmacological therapies have failed for the treatment of short-term severe insomnia, a chloral hydrate 500 mg/5 ml oral solution presentation with an optimised safety profile has been developed as a medication for prescription. Extensive analytical and formulation development work has arrived at a room temperature stable oral solution, with a multiyear expiry date. Key findings: The use of Chloral hydrate in medicinal practice is often associated with high levels of the carcinogen chloroform as a degradation product. The research described herein has shown that the rate of formation of chloroform can be reduced by controlling the impact that the pH has on the stability of the oral solution. The Ph Eur monograph for Chloral hydrate oral solution (unlicensed medicines) does not include a criterion for chloroform quantification, hence Specials manufacturers of this oral solution are potentially risking the safety of patients without appropriate control of chloroform. This research has used validated analytical techniques to support the detection of chloroform, and other possible impurities, thus ensuring a safe product can be provided to the patient.

Degradation of polycyclic aromatic hydrocarbons in oil deodorizer distillates: Kinetics, degradation product identification and toxicity

Polycyclic aromatic hydrocarbons (PAHs) with strong carcinogenicity can cause great threat to human health. However, limited research has focused on the degradation of PAHs in oil deodorizer distillates (ODDs). In this study, E. coli expressing plasmid PodAB were applied in ODD samples to degrade PAHs and compared with white rot fungi (WRF). Prediction model for reactive sites of PAHs and the toxicity of degradation products were developed using density functional theory (DFT) calculations and quantitative structure–activity relationship (QSAR), respectively. The results indicated that the degradation rate of PAHs in ODD reached up to 59.28% using E. coli with the co-expression of pBRCD, which provided the electron carrier. The prediction results using nucleophilic index was consistent with the identification results of GC-MS, which may be more suitable for predicting the PAH oxidation products. Moreover, the R2 of developed QSAR reached 0.8976 for the correlation coefficient between predicted and observed toxicity value, which can be applied to predict the toxicity of degradation products. This work proposes a potential tool for PAH removal in ODD as well as a simple method for predicting PAH oxidation products as well as their toxicity.

Setting of an import tolerance for lambda-cyhalothrin in avocados.

In accordance with Article 6 of Regulation (EC) No 396/2005, the applicant Syngenta Crop Protection AG submitted a request to the competent national authority in Greece to set an import tolerance for the active substance lambda-cyhalothrin in avocados. The data submitted in support of the request were found to be sufficient to derive maximum residue level (MRL) proposals for avocados. Since the general data gap related to toxicity of degradation products formed under sterilisation conditions and identified in the framework of the MRL review has not yet been addressed, a risk management decision is required as to whether it is appropriate to take over the proposed MRLs in the MRL legislation. Adequate analytical methods for enforcement are available to control the residues of lambda-cyhalothrin in the commodity under consideration at the validated limit of quantification (LOQ) of 0.01 mg/kg. Based on the risk assessment results, EFSA concluded that the short-term and long-term intake of residues resulting from the use of lambda-cyhalothrin according to the reported agricultural practice is unlikely to present a risk to consumer health. However, the consumer exposure calculation shall be considered provisional, pending the toxicological assessment of the compounds formed under sterilisation conditions.

Accelerated degradation and toxicity reduction of ribavirin by organic free radicals in the ferrate-acetylacetonate system

This study found that during the degradation of ribavirin (RBV) by ferrate (Fe(VI)) and acetylacetone (AA), organic free radicals significantly accelerated the degradation of ribavirin (RBV) and reduced the toxicity of degradation products. When [Fe(VI)]:[RBV] = 4:1, the pseudo 1st order rate constant of ribavirin removal increased 22.63 times compared with that without AA addition. Through quenching experiments, it was found that quenching of organic free radicals would reduce the degradation efficiency of RBV by 52.88%, while there was no significant effect on the degradation efficiency of RBV after ·OH and Fe(IV)/Fe(V) were quenched. Organic free radical addition products were found in the analysis of intermediate products of RBV degradation in Fe(VI)/AA system, which proved the existence of organic free radicals in Fe(VI)/AA system. Toxicity analysis by ECOSAR found that triazole was the most toxic intermediate product in the degradation process, and analysis of the electrophilic potential points by Dual descriptor found that the carbon-nitrogen double bond on triazole was the most susceptible position for electrophilic attack. The Laplacian bond order was analyzed and found that the addition of organic free radicals decreases the Laplacian bond order of the carbon-nitrogen double bond. The organic free radical (·CH3) generated in the Fe(VI)-AA system facilitated the degradation of RBV and accelerated the toxicity reduction by reducing the bond order of more toxic intermediates.

Efficient degradation of chlorpyrifos and intermediate in soil by a novel microwave induced advanced oxidation process: A two-stage reaction

The application of microwave/peroxymonosulfate (MW/PMS) in soil remediation has been limited by some shortages including low utilization efficiency of oxidants, low MW absorption capacity of soil particles and incomplete degradation of intermediate. In this study, heating pad waste (HPW) was added in the MW/PMS system to increase the ability of absorbing MW and degradation efficiency of toxic intermediate. A two-stage method for degradation of chlorpyrifos (CPF) and its intermediate 3,5,6-trichloro-2-pyridinol (TCP) by MW/PMS assisted with HPW was proposed. In the first stage, more than 90% of CPF was degraded within 15 min before the addition of HPW, and most of the CPF was converted into TCP through direct or indirect pathways under the action of 1O2. In the second stage, more than 70% of the generated TCP was rapidly degraded through SO4•− oxidation and electron transfer. The TCP was further degraded with the assistance of HPW through methylation, hydroxylation and dechlorination etc., and the toxicity of degradation products was decreased significantly. pH and soil organic matter had little influences on CPF and TCP degradation. Therefore, a new strategy for remediation of CPF contaminated-soil was provided based on MW/PMS technology and the concept of “treating waste with waste”.

The Role of Cisternostomy and Cisternal Drainage in the Treatment of Aneurysmal Subarachnoid Hemorrhage: A Comprehensive Review.

Aneurysmal subarachnoid hemorrhage (aSAH) provokes a cascade reaction that is responsible for early and delayed brain injuries mediated by intracranial hypertension, hydrocephalus, cerebral vasospasm (CV), and delayed cerebral ischemia (DCI), which result in increased morbidity and mortality. During open microsurgical repair, cisternal access is achieved essentially to gain proximal vascular control and aneurysm exposition. Cisternostomy also allows brain relaxation, removal of cisternal clots, and restoration of the CSF dynamics through the communication between the anterior and posterior circulation cisterns and the ventricular system, with the opening of the Membrane of Liliequist and lamina terminalis, respectively. Continuous postoperative CSF drainage through a cisternal drain (CD) is a valuable option for treating acute hydrocephalus and intracranial hypertension. Moreover, it efficiently removes the blood and toxic degradation products, with a potential benefit on CV, DCI, and shunt-dependent hydrocephalus. Finally, the CD is an effective pathway to administer vasoactive, fibrinolytic, and anti-oxidant agents and shows promising results in decreasing CV and DCI rates while minimizing systemic effects. We performed a comprehensive review to establish the adjuvant role of cisternostomy and CD performed in cases of direct surgical repair for ruptured intracranial aneurysms and their role in the prevention and treatment of aSAH complications.

Comprehensive Assessment of the Stability of Selected Coxibs in Variable Environmental Conditions along with the Assessment of Their Potential Hepatotoxicity.

Determining the influence of environmental factors on the stability of drugs is very helpful when choosing excipients, storage conditions or packaging materials. In addition, information about possible toxic degradation products enables detecting and avoiding the harmful side effects of the drug. We used the thin-layer chromatographic-densitometric procedure for the assay of five coxibs, conducted degradation studies in various environments and at different temperatures along with the determination of pharmacokinetic parameters. The results were subjected to chemometric analysis, to investigate and visualize the similarities and differences of the studied coxibs. Samples of the tested drug were also analyzed by UPLC-MS/MS in order to identify degradation products, and determine possible drug degradation pathways. Using the human liver cancer HepG2 cell line, the hepatotoxic effect of the degradation products was also determined. It was observed that all substances were relatively stable under the analyzed conditions and degraded more in acidic than alkaline environments. Robenacoxib is the drug that decomposes the fastest, and cimicoxib turned out to be the most stable. Robenacoxib also showed significant hepatotoxicity at the highest tested concentration, which correlates with the high degree of its degradation, and the probable formation of a more hepatoxic product. The obtained mass spectra of compounds formed as a result of hydrolysis of the protonated drug leading to the formation of several product ions, which enabled us to propose probable degradation pathways.

Enhanced photocatalytic degradation of imidacloprid by a simple Z-type binary heterojunction composite of long afterglow with metal-organic framework

Imidacloprid (IMC) is a widely used nicotine-based pesticide that can cause severe harm to water resources. To address this issue, a simple binary heterojunction photocatalyst was constructed to degrade IMC under visible light. Furthermore, the catalyst was able to continue degrading approximately 15% of IMC within 5 h under dark. The possible photocatalytic degradation intermediate's structure and low toxicity were verified by mass spectrometry and zebrafish embryo experiments, respectively. The catalyst also exhibited good stability. Therefore, a simple photocatalyst with excellent performance and low toxicity of degradation products was successfully developed for IMC pesticide removal in water.

The wide presence of fluorinated compounds in common chemical products and the environment: a review.

The C-F bonds, due to their many unique features, have been incorporated into numerous compounds in countless products and applications. These fluorinated compounds eventually are disposed of and released into the environment through different pathways. In this review, we analyzed the occurrence of these fluorinated compounds in seven types of products (i.e., refrigerants/propellants, aqueous film-forming foam, cosmetics, food packaging, agrochemicals, pharmaceuticals, coating materials) and discussed their fate in the environment. This is followed by describing the quantity of fluorinated compounds from each source based on available data. Total on- and off-site disposal or other releases of 536 fluorinated compounds in 2021 were analyzed using the data sourced from the U.S. EPA Toxics Release Inventory (TRI). Among the chemicals examined, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) were the primary contributors in terms of total mass. Upon examining the seven sources of fluorinated compounds, it became evident that additional contributors are also responsible for the presence of organofluorine compounds in the environment. Although various toxic degradation products of fluorinated compounds could form in the environment, trifluoroacetic acid (TFA) was specifically highlighted in this review given the fact that it is a common dead-end degradation product of > 1 million chemicals. This paper ended with a discussion of several questions raised from this study. The path forward was elaborated as well for the purpose of protecting the environment and human health.

Green sustainable assessment of stability indicating first derivative synchronous fluorimetry for determination of anti-diabetic drug with its toxic impurity

Canagliflozin is prescribed with proper diet and exercise for the treatment of type 2 diabetes mellites. In this work, simple and sensitive synchronous fluorescence spectroscopic method coupled with the first derivative was proposed for the quantitative determination of canagliflozin in the presence of its oxidative degradation product. Canagliflozin and its oxidative degradation product have native fluorescence at 353 nm and 364 nm after excitation at 294 nm and 289 nm, respectively. The application of synchronous fluorescence mode gave a sharp peak but failed to resolve canagliflozin and its potential toxic degradation product. First-order derivatization of synchronous spectra resolved the overlap and allowed the determination of canagliflozin in the presence of its oxidative degradation product at 324 nm using Δλ = 20 nm. The method showed linearity with excellent correlation in the concentration range of 1–20 μg/mL for canagliflozin. The method was successfully applied for the determination of canagliflozin in pharmaceutical formulation and laboratory-prepared mixtures with mean percent recovery of 99.95 ± 1.14 and 99.81 ± 1.06, respectively. The greenness of the proposed method was assessed and approved by different tools such as analytical eco-scale, green analytical procedure index GAPI and AGREE.

Mechanistic study of the increased phototoxicity of titanium dioxide nanoparticles to Chlorella vulgaris in the presence of NOM eco-corona

Widespread applications and release of photoactive nanoparticles (NPs) such as titanium dioxide (TiO2) into environmental matrices warrant mechanistic investigations addressing toxicity of NPs under environmentally relevant conditions. Accordingly, we investigated the effects of surface adsorbed natural organic matters (NOMs) such as humic acid, tannic acid and lignin on the band gap energy, abiotic reactive oxygen species (ROS) generation, surface chemistry and phototoxicity of TiO2 NPs. Initially, a liquid assisted grinding method was optimized to produce TiO2 NPs with a NOM layer of defined thickness for further analysis. Generally, adsorption of NOM reduced the band-gap energy of TiO2 NPs from 3.08 eV to 0.56 eV with humic acid, 1.92 eV with tannic acid and 2.48 eV with lignin. Light activated ROS generation by TiO2 NPs such as hydroxyl radicals, however, was reduced by 4, 2, 9 times in those coated with humic acid, tannic acid and lignin, respectively. This reduction in ROS despite decrease in band gap energy corroborated with the decreased surface oxygen vacancy (as revealed by X-ray Photoelectron Spectroscopy (XPS)) and quenching of ROS by surface adsorbed NOM. Despite the reduced ROS generation, the NOM-modified TiO2 NPs exhibited an increased phototoxicity to Chlorella vulgaris in comparison to pristine TiO2 NPs. Further analysis suggested that photoactivation of NOM modified TiO2 NPs releases toxic degradation products. Findings from our studies thus provide mechanistic insight into the ecotoxic potential of NOM-modified TiO2 NPs when exposed to light in the environment.