Degradation Products Research Articles

Degradation of pharmaceuticals and other emerging pollutants employing bi-metal catalysts/magnesium and/or (green) hydrogen in aqueous solution.

Contaminations by pharmaceuticals, personal care products, and other emerging pollutants in water resources have become a seriously burgeoning issue of global concern in the first third of the twenty-first century. As societal reliance on pharmaceuticals continues to escalate, the inadvertent introduction of these substances into water reservoirs poses a consequential environmental threat. Therefore, the aim of this study was to investigate reductive degradation, particularly, catalytic hydrogenation regarding model pollutants such as diclofenac (DCF), ibuprofen (IBP), 17α-ethinylestradiol (EE2), or bisphenol-A (BPA), respectively, in aqueous solutions at lab scale. Iron bimetals (zero valent iron, ZVI, and copper, Cu, or nickel, Ni) as well as zero valent magnesium (Mg, ZVM) in combination with rhodium, Rh, or palladium, Pd, as hydrogenation catalysts (HK), were investigated. Studies were executed through various short-term batch experiments, with multiple sample collections, over a total range of 120min. The results indicated that DCF was attenuated at over 90 % when exposed to Fe-Cu or a Fe-Ni bimetal (applied as a single model pollutant). However, when DCF was part of a mixture alongside with IBP, EE2, and BPA, the attenuation efficacy decreased to 79 % with Fe-Cu and 23 % with Fe-Ni. Conversely, both IBP and BPA exhibit notably low attenuation levels with both bimetals, less than 50 %, both deployed as single substances or in mixtures. No reaction (degradation) products could be identified employing LC-MS, but sometimes a release of the parent pollutant when applying an acetic acid buffer could be noted to a certain extent, suggesting adsorption processes on corrosion products such as iron hydroxide and/or oxides. Surprisingly, Mg in combination with Rh (Rh-HK) or Pd (Pd-HK) showed a significantly rapid decrease in the concentrations of DCF, EE2, and BPA, in part up to approximately 100 %, that is, within a few minutes only in part due to hydrogenation degradation reactions (related reaction products could actually be identified by LC-MS; adsorption processes were not observed here). Moreover, kinetic modeling of the DCF degradation with Mg-Rh-HK was conducted at different temperatures (15 °C, 20 °C, 25 °C, 35 °C) and varied initial concentrations (2.5mg/L, 5.0mg/L, 7.5mg/L, 10.0mg/L). The outcomes prove that the degradation of DCF at the Rh-HK's surface followed a modified first-order kinetics, most probably by catalytic hydrodehalogenation and subsequent hydrogenation of the aromatic moieties (molecular hydrogen was provided by the corrosion of Mg). From the determined reaction rate constants at four different temperatures, the activation energy was estimated to be 59.6kJ/mol by means of the Arrhenius equation what is in good agreement with similar results reported in the literature. This coupled hydrodehalogenation and hydrogenation approach may be upscaled into a new promising technical process for comprehensively removing such pharmaceuticals and similar pollutants in sewage plants in a single step, furthermore, even in combination with adsorption by activated carbon and/or ozonation which have already been established at some sewage plants in Switzerland and Germany recently.

Epoxiconazole degradation in water samples: a comparative study of Fenton, photo-Fenton, solar photo-Fenton, and solar photolysis processes.

Epoxiconazole (EPO) is classified as a persistent organic pollutant due to its ability to persist in the environment for prolonged periods. Its degradation is pivotal in mitigating its environmental impact. This investigation focuses on assessing the degradation of EPO using various methodologies, namely Fenton, photo-Fenton, solar photo-Fenton, and solar photolysis, conducted in both Milli-Q water and groundwater. These experiments encompassed evaluations at both the standard pH typically used in photo-Fenton reactions and the natural pH levels inherent to the respective aqueous environments. Additionally, EPO degradation products were analyzed after a 60-min reaction. Notably, in systems utilizing groundwater, the inclusion of additional iron was unnecessary, as the naturally occurring iron content in the groundwater facilitated the intended processes. Specifically, in Milli-Q water, solar photo-Fenton demonstrated an EPO degradation efficiency of 97%. Furthermore, the substitution of Milli-Q water with groundwater in Fenton-like processes did not significantly affect the efficacy of EPO degradation. These findings underscore the potential of solar photo-Fenton as an economically viable and environmentally sustainable strategy for EPO degradation.

The relationship between serum coagulation parameters and the recurrence of chronic subdural hematoma.

The aim is to investigate the relationship between serum coagulation parameters (PT, APTT, D-D and FDP) before hospitalization and recurrence of chronic subdural hematoma (CSDH). 236 patients with CSDH who were diagnosed for the first time and had complete medical records were followed up for at least 90days. Fifty patients (21.2%) had relapsed. Univariate analysis was conducted including general data, imaging data and test results. Serum coagulation parameters (PT, APTT, D-D and FDP) were detected for all CSDH patients. The study identified several factors that exhibited a significant correlation with chronic subdural hematoma (CSDH) recurrence. These factors included advanced age (p = 0.01), hypertension (p = 0.04), liver disease (p = 0.01), anticoagulant drug use (p = 0.01), antiplatelet drug use (p = 0.02), bilateral hematoma (p = 0.02), and single-layer hematoma (p = 0.01). In addition, the presence of fibrin/fibrinogen degradation products (FDP) exceeding 5mg/L demonstrated a significant relationship with CSDH recurrence (P < 0.05). Notably, the combined assessment of D-dimer (D-D) and FDP exhibited a significant difference, particularly regarding recurrence within 30days after surgery (P < 0.05). The simultaneous elevation of serum FDP and D-D levels upon admission represents a potentially novel predictor for CSDH recurrence. This finding is particularly relevant for patients who experience recurrence within 30days following surgical intervention. Older individuals with CSDH who undergo trepanation and drainage should be closely monitored due to their relatively higher recurrence rate.

Sensitive and validated UPLC-MS/MS method for the identification and characterization of forced degradation products for felodipine

AbstractA rapid, stability indicating reverse phase liquid chromatographic method was developed for the determination of purity of Felodipine in active pharmaceutical substance form in the presence of its impurity and its degradation products. To develop the method which is also compatible to liquid chromatographic mass spectroscopic technique. The developed method is also used to determine the assay of Felodipine in bulk drug form. The drug is subjected to various stress conditions like acidic, basic, oxidation, UV light and thermal conditions. Considerable degradation was observed during base hydrolysis. Two degradation products were identified. The Waters Acquity UPLC BEH C18, 2.1 × 100 mm, 1.7 µm Column was used to achieve chromatographic separation. The gradient conditions, diluent and injection volume were optimized to achieve the acceptable resolution between impurities and its degradation products from Felodipine and to get good peak shapes. The masses were determined for main compound and its identified degradation products. Further, the characterization studies for main compound and its degradation products were performed using LCMSMS Q-TOF.

Rapid biotransformation of STW 5 constituents by human gut microbiome from IBS- and non-IBS donors.

STW 5 is an herbal medicinal product with proven clinical efficacy in the treatment of functional gastrointestinal disorders, like functional dyspepsia and irritable bowel syndrome (IBS). The effects of STW 5 on fecal microbial communities and metabolite production effects have been studied in an experimental model with fecal samples from individuals with and without IBS. While only minor taxonomic disparities were noted between IBS- and non-IBS samples and upon treatment with STW 5, rapid metabolic turnover of STW 5 components into specific degradation products with reported anti-inflammatory, cytoprotective, or spasmolytic activities was observed, which may be relevant for the pharmacological activity of STW 5.

The Unprecedented Biodegradable Polyzwitterion: A Removal-Free Patch for Accelerating Infected Diabetic Wound Healing.

Zwitterionic polymers have emerged as an important class of biomaterials to construct wound dressings and antifouling coatings over the past decade due to their excellent hydrophilicity. However, all the reported zwitterionic polymers are non-degradable because of non-cleavable carbon-carbon bonding backbones, and must be removed periodically after treatment to avoid hypoxia in the wound, thus leading to potential secondary injury. In this work, we fabricate a biodegradable polyzwitterion patch for the first time by ring-opening polymerization of carboxybetaine dithiolane (CBDS), which is self-crosslinked via inter-amide hydrogen bonds and zwitterionic dipole-dipole interactions on the side chains. The unprecedented polyCBDS (PCBDS) patch demonstrates enough ductility owing to the intermolecular physical interactions to fully cover irregular wounds, also showing excellent biodegradability and antifouling performance resulted from the existence of disulfide bonds and carboxybetaine groups. Besides, the PCBDS degradation-induced released CBDS owns potent antioxidant and antibacterial activities. This PCBDS patch is used as a diabetic wound dressing, inhibiting bacterial adhesion on the external surface, and its degradation products can exactly kill bacteria and scavenge reactive oxygen species at the wound site to regulate local microenvironment, including regulation of cytokine express and macrophage polarization, accelerating infected diabetic wound repair and also avoiding the potential secondary injury. This article is protected by copyright. All rights reserved.

Biotransformation of aflatoxin B1 by a novel strain Brevundimonas sp. LF-1

Aflatoxin B1 (AFB1) is a potent mycotoxin and a common source of food and feed contamination, posing risks to both human and animal health. The biotransformation of AFB1 has been proven to be a promising approach to control AFB1 contamination. In this study, Brevundimonas sp. LF-1 capable of degrading AFB1 was isolated from a corn-planted soil sample. Strain LF-1 could degrade 86.90% of 2 mg L−1 AFB1 after incubation in Luria-Bertani (LB) medium at 30 °C for 72 h and exhibited high performance when exposed to up to 10.0 mg L−1 AFB1. The optimum pH and temperature were 7.0–10.0 and 30 °C, respectively. The results of the in vitro cytotoxicity assay showed that the degradation products had considerably (p < 0.05) less harmful effects than the parent AFB1. Additionally, strain LF-1 possessed the bioremediation potential of AFB1 contamination for biocontrol strategies in animal fodder. Two putative novel AFB1-degrading enzymes, peroxiredoxin 1 and peroxiredoxin 2, were identified in the genome of strain LF-1. Comparative genomics indicated that the peroxiredoxin enzyme was widely distributed in the genus Brevundimonas. The comprehensive examination of strain LF-1 has outstanding potential for the development of detoxifying agents for AFB1 in the food and feed industries.

Development and Evaluation of Chemometric Models for the Estimation of Sumatriptan in the Presence of Naproxen and a Degradation Product Using UV Spectrophotometry.

Chemometrics is a discipline that allows the spectral resolution of drugs in a pharmaceutical formulation along with degradation product and it is as an alternative to chromatographic methods. Sumatriptan (SUM) is co-formulated with naproxen (NAP) and used in acute migraine attacks. SUM which has physiological importance has not been subjected to any stability-indicating chemometric approaches yet so there is a need for accurate and safe method for the assay of the cited drug in their preparation. SUM was determined in pharmaceutical formulation along with NAP and in presence of alkali-induced degradation product with simple and cost-effective multivariate approaches using spectrophotometric data. The greenness and blueness assessment was applied using different ecological metrics, including green analytical procedure index (GAPI), analytical greenness metric (AGREE), analytical eco-scale (AES) & new "blueness" evaluation using BAGI tool, respectively. Three chemometric approaches were applied for the stability-indicating determination of SUM in presence of NAP. Classical least squares (CLS), Partial least squares (PLS) and Principal components regression (PCR), three multivariate calibration numerical models that were performed on the UV- spectra of the mixtures, were used to achieve the best resolution. Sumatriptan was analyzed with mean accuracies for PLS (100.29 ± 1.318) and for PCR (100.60 ± 1.564). The presented methods were compared and validated for their quantitative analyses. Moreover, statistical comparison between the results obtained by the proposed models and the official methods showed no significant differences. The proposed multivariate calibrations were accurate and specific for quantitative analysis of the studied component. PLS is the best method that has the capacity for qualitative analysis of SUM and it is suitable for routine analysis and stability studies of it in quality control laboratories. Various ecological assessment metrics confirmed the long-standing eco-friendliness of the suggested models.

Stability-Indicating HPLC Method for Determination of Ibuprofen and Famotidine Degradation Products.

A new stability-indicating high-performance liquid chromatographic method for the quantitative determination of ibuprofen and famotidine degradation products in combined pharmaceutical products was developed and validated. The current aim of this study is to develop a rapid, accurate and robust analytical stability indicating impurity method that can separate ibuprofen, famotidine and their related impurities by using a reversed-phase high-performance liquid chromatography. A Zorbax SB-Phenyl column (4.6 × 150mm2, 5-μm particle size) with mobile phase containing phosphate buffer solution with a pH value of 3.0 and acetonitrile was used. The flow rate was 0.8mL/min and the analytes were detected by UV detector at 265nm. The retention times of ibuprofen and famotidine were 18.43 and 5.14min, respectively. This method was validated to confirm specificity, linearity, sensitivity (limit of detection and limit of quantitation), precision, accuracy, robustness and sample stability according to the International Conference on Harmonization guidelines. Studies have been completed and reported with two active substances in the combined dosage form and seven impurities in total. There is no method in the literature that simultaneously distinguishes and quantitatively analyzes both active substances and degradation products.

The Elimination of Levofloxacin from High-Salinity Wastewater via the Electrochlorination Process

The electrochlorination (E-Cl) process has attracted much attention as it is a highly efficient method for treating organic compounds in hypersaline wastewater. In this study, the E-Cl process was utilized for the removal of antibiotics. The optimal experimental conditions were determined to be a NaCl concentration of 100 mM, a current density of 1.5 mA/cm2, a pH of 7.0, and a plate spacing of 1 cm, with a levofloxacin (LEV) degradation efficiency reaching as high as 99% using this setup. The effects of the presence of other ions and humic acid on the E-Cl process were investigated, and it was found that the degradation of LEV was not significantly affected by the presence of coexisting substances. In addition, free chlorine was identified as the primary active species for the degradation of LEV by means of a quenching experiment. It was demonstrated by 3D EEM and TOC that LEV was not completely mineralized and that intermediate products may be present. In order to reveal the degradation pathways of LEV, its degradation products were also analyzed via LC-MS, and some possible pathways of LEV degradation in this system were proposed. The successful degradation of LEV demonstrated that the E-Cl process is an efficient and promising technique for the treatment of organic pollutants in high-salinity wastewater.

Exploring the Influence of Cold Plasma on Epidermal Melanogenesis In Situ and In Vitro

Epidermal melanin synthesis determines an individual’s skin color. In humans, melanin is formed by melanocytes within the epidermis. The process of melanin synthesis strongly depends on a range of cellular factors, including the fine-tuned interplay with reactive oxygen species (ROS). In this context, a role of cold atmospheric plasma (CAP) on melanin synthesis was proposed due to its tunable ROS generation. Herein, the argon-driven plasma jet kINPen® MED was employed, and its impact on melanin synthesis was evaluated by comparison with known stimulants such as the phosphodiesterase inhibitor IBMX and UV radiation. Different available model systems were employed, and the melanin content of both cultured human melanocytes (in vitro) and full-thickness human skin biopsies (in situ) were analyzed. A histochemical method detected melanin in skin tissue. Cellular melanin was measured by NIR autofluorescence using flow cytometry, and a highly sensitive HPLC-MS method was applied, which enabled the differentiation of eu- and pheomelanin by their degradation products. The melanin content in full-thickness human skin biopsies increased after repeated CAP exposure, while there were only minor effects in cultured melanocytes compared to UV radiation and IBMX treatment. Based on these findings, CAP does not appear to be a useful option for treating skin pigmentation disorders. On the other hand, the risk of hyperpigmentation as an adverse effect of CAP application for wound healing or other dermatological diseases seems to be neglectable.

Analysis of COF-300 synthesis: probing degradation processes and 3D electron diffraction structure.

Although COF-300 is often used as an example to study the synthesis and structure of (3D) covalent organic frameworks (COFs), knowledge of the underlying synthetic processes is still fragmented. Here, an optimized synthetic procedure based on a combination of linker protection and modulation was applied. Using this approach, the influence of time and temperature on the synthesis of COF-300 was studied. Synthesis times that were too short produced materials with limited crystallinity and porosity, lacking the typical pore flexibility associated with COF-300. On the other hand, synthesis times that weretoo long could be characterized by loss of crystallinity and pore order by degradation of the tetrakis(4-aminophenyl)methane (TAM) linker used. The presence of the degradation product was confirmed by visual inspection, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). As TAM is by far the most popular linker for the synthesis of 3D COFs, this degradation process might be one of the reasons why the development of 3D COFs is still lagging compared with 2D COFs. However, COF crystals obtained via an optimized procedure could be structurally probed using 3D electron diffraction (3DED). The 3DED analysis resulted in a full structure determination of COF-300 at atomic resolution with satisfying data parameters. Comparison of our 3DED-derived structural model with previously reported single-crystal X-ray diffraction data for this material, as well as parameters derived from the Cambridge Structural Database, demonstrates the high accuracy of the 3DED method for structure determination. This validation might accelerate the exploitation of 3DED as a structure determination technique for COFs and other porous materials.

Indium Tin Oxide Induced Internal Positive Feedback and Indium Ion Transport in Perovskite Solar Cells.

Stability is the most pressing challenge hindering the commercialization of perovskite solar cells (PSCs), and previous efforts focused more on enhancing the resistance of PSCs to external stimulus. Here, we found that the indium tin oxide (ITO) will deteriorate the photovoltaic performance of PSCs through positive feedback cycles. Specifically, the perovskite degradation products will cross the electron transport layer to chemically etch the electrode ITO to generate In3+, which will migrate upwards into the perovskite film. Then, the reaction that corrodes ITO consumes the decomposition products of perovskite and shifts the balance of the perovskite decomposition reaction, further promoting the degradation and thus falling into a positive feedback cycle. Moreover, the In3+ in the perovskite film was found to accumulate at the upper surface, which would lead to n-type doping of perovskite film to form the energy barrier for interface carrier extraction. Subsequently, the chelating molecule ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) was introduced onto ITO to firmly chelate the In3+ and prevent it from migrating upward, thus breaking this internal positive feedback cycle and significantly enhancing the efficiency and stability of PSCs. This work provides new perspectives for understanding the mechanism of photovoltaic performance loss and ionic transport in PSCs.

Biodegradation of low-density polyethylene film by two bacteria isolated from plastic debris in coastal beach

Low-density polyethylene (LDPE) conduces massive environmental accumulation due to its high production and recalcitrance to environment. In this study, We successfully enriched and isolated two strains, Nitratireductor sp. Z-1 and Gordonia sp. Z-2, from coastal plastic debris capable of degrading LDPE film. After a 30-day incubation at 30 ℃, strains Z-1 and Z-2 decreased the weight of branched-LDPE (BLDPE) film by 2.59 % and 10.27 % respectively. Furthermore, high temperature gel permeation chromatography (HT-GPC) analysis revealed molecular weight reductions of 7.69 % (Z-1) and 23.22 % (Z-2) in the BLDPE film. Scanning electron microscope (SEM) image showed the presence of microbial colonization and perforations on the film's surface. Fourier transform infrared spectroscopy (FTIR) analysis indicated novel functional groups, such as carbonyl and carbon-carbon double bonds in LDPE films. During LDPE degradation, both strains produced extracellular reactive oxygen species (ROS). GC-MS analysis revealed the degradation products included short-chain alkanes, alkanols, fatty acids, and esters. Genomic analysis identified numerous extracellular enzymes potentially involved in LDPE chain scission. A model was proposed suggesting a coordinated role between ROS and extracellular enzymes in the biodegradation of LDPE. This indicates strains Z-1 and Z-2 can degrade LDPE, providing a basis for deeper exploration of biodegradation mechanisms.

Emerging Alternaria toxins present in naturally contaminated dried tomatoes and their reduction using cold atmospheric plasma

This study investigated the efficacy of cold atmospheric plasma (CAP) treatment in degrading the emerging Alternaria toxins as pure molecules and as natural contaminants in dried tomatoes. The analyses of 25 batches of dried tomatoes showed that more than 40% of samples were contaminated with tenuazonic acid (TeA), one with Alternariol (AOH), while Tentoxin (TEN), Alternariol monomethyl ether (AME) and Altenuene (ALT) were not detected. CAP under ozone (O3) and NOx regimes were used to reduce the mycotoxin contamination, the results shown that O3 regime was more effective against all mycotoxins tested, while NOx regime showed different efficacy depending on the specific mycotoxin. The Weibull model proved to be appropriate for the degradation kinetics of all Alternaria toxins, regardless of the kinetic order they possess. Under the O3 regime, the resistance of the mycotoxin was AME > AOH > TEN > TeA > ALT. Our studies have shown for the first time that CAP reduces Alternaria toxins in naturally contaminated dried tomatoes. In particular, the rate of degradation under O3 regime increased significantly with the longest exposure time, reaching 52.80 ± 1.21 % of mycotoxin degradation. Our results expand our knowledge of CAP treatment as a potential means of reducing mycotoxin contamination in food. Further studies will be carried out to investigate the potential mycotoxin degradation products and to ensure food safety.

Indium Tin Oxide Induced Internal Positive Feedback and Indium Ion Transport in Perovskite Solar Cells

Stability is the most pressing challenge hindering the commercialization of perovskite solar cells (PSCs), and previous efforts focused more on enhancing the resistance of PSCs to external stimulus. Here, we found that the indium tin oxide (ITO) will deteriorate the photovoltaic performance of PSCs through positive feedback cycles. Specifically, the perovskite degradation products will cross the electron transport layer to chemically etch the electrode ITO to generate In3+, which will migrate upwards into the perovskite film. Then, the reaction that corrodes ITO consumes the decomposition products of perovskite and shifts the balance of the perovskite decomposition reaction, further promoting the degradation and thus falling into a positive feedback cycle. Moreover, the In3+ in the perovskite film was found to accumulate at the upper surface, which would lead to n‐type doping of perovskite film to form the energy barrier for interface carrier extraction. Subsequently, the chelating molecule ethylenediaminetetraacetic acid disodium salt (EDTA‐2Na) was introduced onto ITO to firmly chelate the In3+ and prevent it from migrating upward, thus breaking this internal positive feedback cycle and significantly enhancing the efficiency and stability of PSCs. This work provides new perspectives for understanding the mechanism of photovoltaic performance loss and ionic transport in PSCs.

Thermophysical Behavior of Carbonated Aqueous Solutions Containing Monoethanolamine and Degradation Products

Thermophysical Behavior of Carbonated Aqueous Solutions Containing Monoethanolamine and Degradation Products

The Synthesis of Ag/TiO2 via the DC Magnetron Sputtering Method and Its Application in the Photocatalytic Degradation of Methyl Orange in Na2SO4 Solution

TiO2 and TiO2 films modified with Ag (Ag/TiO2) were prepared via the DC magnetron sputtering method and the degree of modification was controlled via the sputtering power and time of Ag. The microstructures and properties of these films were characterized using field emission scanning electron microscopy, X-ray diffractometry, ultraviolet–visible diffuse reflectance spectrometry, atomic force microscopy, and X-ray photoelectron spectroscopy (XPS). The results show that the prepared films have an anatase structure. Compared with pure TiO2, Ag deposition can improve the utilization of light. The three-dimensional images of Ag/TiO2 clearly show that with the increase in Ag sputtering power and sputtering time, Ag particles on the surface of the film gradually increase, and the structure of the film is relatively dense. The photocatalytic effect of Ag/TiO2 films is the best when the Ag sputtering power is 5 W and the sputtering time is 50 s. Under high-pressure mercury lamp irradiation, the photocatalytic degradation rate of methyl orange (MO) in pure MO solution with Ag/TiO2-5 W-50 s can reach 100% within 55 min, whereas that in MO-Na2SO4 mixed solution can reach 99.55% within 65 min. The results suggest that the presence of Na2SO4 in MO solution can inhibit the degradation of MO using Ag/TiO2, the result of XPS suggests that Na2SO4 accelerates the oxidation of Ag, which may lead to an increase in the recombination rate of photogenerated electron–hole pairs and a decrease in the degradation rate. During the process of recycling photocatalysts, the degradation rate of MO was apparently reduced. A possible reason is that the Ag particles have been oxidized and products of photocatalytic degradation are on the surface of the photocatalyst. The photocatalytic degradation mechanism was studied.

LC and LC-MS/MS Studies for the Separation and Identification of Impurities and Degradation Products of Betaxolol.

Betaxolol (Bx) is a selective β1 receptor blocker used in the treatment of hypertension and glaucoma. The aim of the present work was to demonstrate an approach involving use of liquid chromatography (LC) and liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS) for the simultaneous separation, identification and characterization of impurities and of degradation products of betaxolol without their isolation from the reaction mixtures. At optimum condition, and according to ICH guidelines, the limit of detection (LOD) and limit of quantification (LOQ) for Bx are found to be 5.46 and 16.54μgmL-1, respectively. However, the LOD and LOQ for the major degradation product P6 were 2.15 and 6.53μgmL-1. Betaxolol was subjected to hydrolytic (acidic and basic) and oxidative, stress conditions according to International Conference on Harmonization (ICH) guideline Q1A (R2), and as results, the drug was found to be labile in acidic, basic and oxidative stress conditions. Based on LC-ESI/MS analysis, the found results revealed that Bx decomposes in acidic, basic and oxidizing environments. All degradation products were identified with the help of their fragmentation pattern and the masses obtained upon the MS analysis.

Effects of Pesticides Use on Pesticides Residues and Its Environmental Risk Assessment in Xingkai Lake（China）

Xingkai Lake, located in Heilongjiang Province, is an important fishery and agricultural base and is seriously polluted by agricultural non-point sources. To clarify the residual status of many pesticides in the surface water of Xingkai Lake, 27 types of pesticides, herbicides, and their degradation products were analyzed in rice paddy, drainage, and surface water around Xingkai Lake (China) during the rice heading and maturity periods. The results showed that all 27 types of pesticides, herbicides, and their degradation products were detected during the rice heading period, and the total concentration ranged from 247.97 to 6 094.49 ng·L-1. Additionally, 25 species were detected during the rice maturity period, and the total concentration ranged from 485.36 to 796.23 ng·L-1. In comparison, more pesticides, herbicides, and derived degradation products were detected during the heading period, and their total concentration was higher as well. During the rice heading period, atrazine, simetryn, and paclobutrazol were the main detected pesticides, atrazine and isoprothiolane were the main pesticides detected during the maturity period. The distribution characteristics of pesticides and herbicides in the surface water around Xingkai Lake (China) was similar to that in drainage, so they were probably imported from the drainage and rice paddy. The average risk quotient (RQ) values of atrazine, simetryn, prometryn, butachlor, isoprothiolane, and oxadiazon were higher than 0.1 in drainage and Xingkai Lake (China), which showed a potential risk to aquatic organisms.