Harnessing solar power for enhanced photocatalytic degradation of coloured pollutants using novel Mg-doped-ZnFe2O4/S@g-C3N4 heterojunction: A facile hydrothermal synthesis approach.

The ability of heterogeneous photocatalysis to effectively remove organic pollutants from wastewater has shown great promise as a tool for environmental remediation. Pure zinc ferrites (ZnFe2O4) and magnesium-doped zinc ferrites (Mg@ZnFe2O4) with variable percentages of Mg (0.5, 1, 3, 5, 7, and 9 mol%) were synthesized via hydrothermal route and their photocatalytic activity was checked against methylene blue (MB) taken as a model dye. FTIR, XPS, BET, PL, XRD, TEM, and UV-Vis spectroscopy were used for the identification and morphological characterization of the prepared nanoparticles (NPs) and nanocomposites (NCs). The 7% Mg@ZnFe2O4 NPs demonstrated excellent degradation against MB under sunlight. The 7% Mg@ZnFe2O4 NPs were integrated with diverse contents (10, 50, 30, and 70 wt.%) of S@g-C3N4 to develop NCs with better activity. When the NCs were tested to degrade MB dye, it was revealed that the 7%Mg@ZnFe2O4/S@g-C3N4 NCs were more effective at utilizing solar energy than the other NPs and NCs. The synergistic effect of the interface formed between Mg@ZnFe2O4 and S@g-C3N4 was primarily responsible for the boosted photocatalytic capability of the NCs. The fabricated NCs may function as an effective new photocatalyst to remove organic dyes from wastewater.

Photocatalytic degradation of antibiotics and antimicrobial and anticancer activities of two-dimensional ZnO nanosheets.

Active pharmaceutical ingredients have emerged as an environmentally undesirable element because of their widespread exploitation and consequent pollution, which has deleterious effects on living things. In the pursuit of sustainable environmental remediation, biomedical applications, and energy production, there has been a significant focus on two-dimensional materials (2D materials) owing to their unique electrical, optical, and structural properties. Herein, we have synthesized 2D zinc oxide nanosheets (ZnO NSs) using a facile and practicable hydrothermal method and characterized them thoroughly using spectroscopic and microscopic techniques. The 2D nanosheets are used as an efficient photocatalyst for antibiotic (herein, end-user ciprofloxacin (CIP) was used as a model antibiotic) degradation under sunlight. It is observed that ZnO NSs photodegrade ~ 90% of CIP within two hours of sunlight illumination. The molecular mechanism of CIP degradation is proposed based on ex-situ IR analysis. Moreover, the 2D ZNO NSs are used as an antimicrobial agent and exhibit antibacterial qualities against a range of bacterial species, including Escherichia coli, Staphylococcus aureus, and MIC of the bacteria are found to be 5 µg/l and 10 µg/l, respectively. Despite having the biocompatible nature of ZnO, as-synthesized nanosheets have also shown cytotoxicity against two types of cancer cells, i.e. A549 and A375. Thus, ZnO nanosheets showed a nontoxic nature, which can be exploited as promising alternatives in different biomedical applications.

Photo-catalytic dye degradation potentials of Ag-Pd bimetallic nanoparticles synthesized from Vitex negundo.

Plant extracts are a great alternative to synthesizing nanoparticles of different metals and metal oxides. This green synthesis method has opened up numerous possibilities in various scientific domains. In present study, Leaf extract from Vitex negundo is a non-deciduous, long-lasting shrub from the Verbenaceae family is used as capping and reducing agents for the synthesis of silver and palladium nanoparticles. The characterization study UV-vis spectrophotometer analysis showed absorbance value around 320 nm which confirming that Ag-Pd nanoparticles have been successfully obtained. Further, SEM is used to investigate the morphology of Ag-Pd NPs, which revealing their spherical and rod-like configuration, aggregation, and the size of the particles are obtained between 50 and 100 nm. The successful synthesis of Ag-Pd NPs was further confirmed by the EDAX chart, which displayed the peak of Ag and Pd at bending energies between 0.5 and 1.5 keV. According to the quantitative study, Ag and Pd ions found about 5.24 and 13.28%, respectively. In addition, surface studies with TEM confirming that synthesized Ag-Pd NPs are predominates with spheres structure morphologies, with sizes averaging 11.20 nm and ranging from 10 to 20 nm. Further, Ag-Pd nanoparticles was applied as potential photocatalyst materials to degrade methylene blue dye and found about 85% of the degradation efficiency within 150 min of the sunlight exposure thus could be used as catalyst to removal of hazardous organic dye molecules.

Effect of Morphology Modification of BiFeO3 on Photocatalytic Efficacy of P-g-C3N4/BiFeO3 Composites.

This current study assessed the impacts of morphology adjustment of perovskite BiFeO3 (BFO) on the construction and photocatalytic activity of P-infused g-C3N4/U-BiFeO3 (U-BFO/PCN) heterostructured composite photocatalysts. Favorable formation of U-BFO/PCN composites was attained via urea-aided morphology-controlled hydrothermal synthesis of BFO followed by solvosonication-mediated fusion with already synthesized P-g-C3N4 to form U-BFO/PCN composites. The prepared bare and composite photocatalysts' morphological, textural, structural, optical, and photocatalytic performance were meticulously examined through various analytical characterization techniques and photodegradation of aqueous rhodamine B (RhB). Ellipsoids and flakes morphological structures were obtained for U-BFO and BFO, and their effects on the successful fabrication of the heterojunctions were also established. The U-BFO/PCN composite exhibits 99.2% efficiency within 20 min of visible-light irradiation, surpassing BFO/PCN (88.5%), PCN (66.8%), and U-BFO (26.1%). The pseudo-first-order kinetics of U-BFO/PCN composites is 2.41 × 10-1 min-1, equivalent to 2.2 times, 57 times, and 4.3 times of BFO/PCN (1.08 × 10-1 min-1), U-BFO, (4.20 × 10-3 min-1), and PCN, (5.60 × 10-2 min-1), respectively. The recyclability test demonstrates an outstanding photostability for U-BFO/PCN after four cyclic runs. This improved photocatalytic activity exhibited by the composites can be attributed to enhanced visible-light utilization and additional accessible active sites due to surface and electronic band modification of CN via P-doping and effective charge separation achieved via successful composites formation.

Photodegradation enhances the toxic effect of anthracene on skin.

Anthracene, a polycyclic aromatic hydrocarbon (PAH), is a widespread environmental pollutant that poses potential risks to human health. Exposure to anthracene can result in various adverse health effects, including skin-related disorders. Photo exposure sufficiently removes the anthracene from the environment but also generates more degradation products which can be more toxic. The goal of this study was to assess the change in anthracene dermotoxicity caused by photodegradation and understand the mechanism of this change. In the present study, over 99.99% of anthracene was degraded within 24 h of sunlight exposure, while producing many intermediate products including 9,10-anthraquinone and phthalic acid. The anthracene products with different durations of photo exposure were applied to 2D and 3D human keratinocyte cultures. Although the non-degraded anthracene significantly delayed the cell migration, the cell viability and differentiation decreased dramatically in the presence of the photodegraded anthracene. Anthracene photodegradation products also altered the expression patterns of a number of inflammation-related genes in comparison to the control cells. Among these genes, il1a, il1b, il8, cxcl2, s100a9, and mmp1 were upregulated whereas the tlr4 and mmp3 were downregulated by the photodegraded anthracene. Topical deliveries of the photodegraded and non-degraded anthracene to the dorsal skin of hairless mice showed more toxic effects by the photodegraded anthracene. The 4-hour photodegradation products of anthracene thickened the epidermal layer, increased the dermal cellularity, and induced the upregulation of inflammatory markers, il1a, il1b, s100a9, and mmp1. In addition, it also prevented the production of a gap junction protein, Connexin-43. All the evidence suggested that photodegradation enhanced the toxicities of anthracene to the skin. The 4-hour photodegradation products of anthracene led to clinical signs similar to acute inflammatory skin diseases, such as atopic and contact dermatitis, eczema, and psoriasis. Therefore, the potential risk of skin irritation by anthracene should be also considered when an individual is exposed to PAHs, especially in environments with strong sunlight.

Insight into pyrrolizidine alkaloids degradation and the chemical structures of their degradation products using ultra high performance liquid chromatography and Q-Exactive Orbitrap mass spectrometry.

Pyrrolizidine alkaloids (PAs), released into the environment by donor plants, are absorbed by crops or transported by animals, posing a global food safety concern. Photolysis is an effective way to eliminate harmful substances in the environment or food. Photolysis happens as PAs move among plants, environment and crops. In this study, we first investigated the photolysis and hydrolysis of 15 PAs and identified their degradation products via ultra-high performance liquid chromatography and Q-Exactive Orbitrap mass spectrometry. PAs were degraded under UV radiation but minimally affected by visible light from a xenon lamp, and solvent pH had little impact on their photolysis. PAs were stable in neutral and acidic solutions but degraded by 50% within 24 h in alkaline conditions. The degradation products of PAs were mainly PAs/PANOs isomers and some minor byproducts. Cytotoxicity and computational analysis revealed isomers had similar toxicity, with minor products being less toxic. This study is a precursor for revealing the potential PAs degradation dynamics in the environment and food products, providing a reference for systematic evaluations of potential health and ecological risks of their degradation products.

CdIn2Se4@chitosan heterojunction nanocomposite with ultrahigh photocatalytic activity under sunlight driven photodegradation of organic pollutants.

This research focused on synthesizing a CdIn2Se4@Ch nanocomposite by doping CdIn2Se4 into chitosan using a photolysis assisted ultrasonic process. The aim was to enhance the photodegradation efficiency of ofloxacin and 2,4-dichlorophenoxyacetic acid under sunlight. The synthesized CdIn2Se4@Ch nanocomposite was investigated via different techniques, including XRD, XPS, FTIR, TEM, DSC, TGA, UV-Vis and PL. The study also investigated the influence of various reaction parameters, including the effects of inorganic and organic ions. The synthesized nanocomposite demonstrated exceptional efficiency, achieving 86 % and 95 % removal rates, with corresponding rate constants of 0.025 and 0.047 min-1. This performance surpasses that of CdIn2Se4 by approximately 1.35 and 2.25 times, respectively. The values of COD were decreased to 78 and 86 % for ofloxacin and 2,4-dichlorophenoxyacetic, while the TOC values decreased to 71 and 84 %, respectively, from their premier values. The improvement in performance is associated with the introduction of CdIn2Se4 into chitosan, resulting in the self-integration of Cd into the catalyst. This creates a localized accumulation point for electrons, enhancing the efficiency of charge separation and further reducing the surface charge of chitosan. Experimental evidence suggests that superoxide and hydroxyl radicals play a significant role in the photodegradation of pollutants. Additionally, the nanocomposite exhibits excellent stability and can be reused up to five times, indicating remarkable stability and reusability of the developed photocatalyst.

A novel BiOBr/rGO photocatalysts for degradation of organic and antibiotic pollutants under visible light irradiation: Tetracycline degradation pathways, kinetics, and mechanism insight.

In this study, the BiOBr/rGO nanocomposite photocatalysts are fabricated by a facile solvothermal method. The BiOBr growth on reduced graphene oxide (rGO) sheet could improve BiOBr's photocatalytic activity by increasing its adsorption ability, surface area, and charge carriers' separation efficiency. The prepared nanocomposites were characterized by XRD, Raman, FESEM, EDS, XPS, and UV-visible DRS. The BiOBr/rGO (BRG) nanocomposites showed improved photocatalytic activity for the photodegradation of Rhodamine B (RhB) dye and Tetracycline (TC) under visible light irradiation. Rhodamine B and tetracycline degradation efficiency were about 96% and 73% within 120 min under visible light irradiation. The PL analysis indicates that BiOBr/rGO nanocomposite exhibited maximum separation efficiency of photoinduced charge carriers. The trapping test confirmed that O2- and h+ are significant active photodegradation species. The GC-MS spectra detected the two plausible transformation routes of tetracycline degradation. The current work presented a low-cost and facile approach for fabricating Bi-based composites.

TiO2 nanorod decorated with MoS2 nanospheres: An efficient dual-functional photocatalyst for antibiotic degradation and hydrogen production.

The design and preparation of dual-functional photocatalysts for simultaneously realizing photocatalytic wastewater purification and hydrogen energy generation pose significant challenges. This article presents the engineering of a binary heterostructured photocatalyst by combining TiO2 (nanorods) and MoS2 nanosphere using a straightforward solvothermal method and the assessment of the phase structures, morphologies, and optical properties of the resulting nanocomposites using diverse analytical techniques. The TiO2(Rod)/MoS2 composite exhibits remarkable efficacy in degrading ciprofloxacin, achieving 93% removal rate within 1 h, which is four times higher than that of bare TiO2. Moreover, the optimized TiO2(Rod)/MoS2 presents an outstanding hydrogen production rate of 7415 µmol g-1, which is ∼24 times higher than that of pristine TiO2. Under UV-visible light irradiation, the TiO2(Rod)/MoS2 heterojunction displays an exceptional photocatalytic performance in terms of both photodegradation and hydrogen production, surpassing the performance of TiO2 particle/MoS2. The study findings demonstrate that TiO2(Rod)/MoS2 nanocomposites exhibit considerably improved photocatalytic degradation and hydrogen generation activities. Based on the experimental results, a possible mechanism is proposed for the transfer and separation of charge carriers in Z-scheme heterojunctions.

The Fabrication and Property Characterization of a Ho2YSbO7/Bi2MoO6 Heterojunction Photocatalyst and the Application of the Photodegradation of Diuron under Visible Light Irradiation.

A novel photocatalytic nanomaterial, Ho2YSbO7, was successfully synthesized for the first time using the solvothermal synthesis technique. In addition, a Ho2YSbO7/Bi2MoO6 heterojunction photocatalyst (HBHP) was prepared via the hydrothermal fabrication technique. Extensive characterizations of the synthesized samples were conducted using various instruments, such as an X-ray diffractometer, a Fourier transform infrared spectrometer, a Raman spectrometer, a UV-visible spectrophotometer, an X-ray photoelectron spectrometer, and a transmission electron microscope, as well as X-ray energy dispersive spectroscopy, photoluminescence spectroscopy, a photocurrent test, electrochemical impedance spectroscopy, ultraviolet photoelectron spectroscopy, and electron paramagnetic resonance. The photocatalytic activity of the HBHP was evaluated for the degradation of diuron (DRN) and the mineralization of total organic carbon (TOC) under visible light exposure for 152 min. Remarkable removal efficiencies were achieved, with 99.78% for DRN and 97.19% for TOC. Comparative analysis demonstrated that the HBHP exhibited markedly higher removal efficiencies for DRN compared to Ho2YSbO7, Bi2MoO6, or N-doped TiO2 photocatalyst, with removal efficiencies 1.13 times, 1.21 times, or 2.95 times higher, respectively. Similarly, the HBHP demonstrated significantly higher removal efficiencies for TOC compared to Ho2YSbO7, Bi2MoO6, or N-doped TiO2 photocatalyst, with removal efficiencies 1.17 times, 1.25 times, or 3.39 times higher, respectively. Furthermore, the HBHP demonstrated excellent stability and reusability. The mechanisms which could enhance the photocatalytic activity remarkably and the involvement of the major active species were comprehensively discussed, with superoxide radicals identified as the primary active species, followed by hydroxyl radicals and holes. The results of this study contribute to the advancement of efficient heterostructural materials and offer valuable insights into the development of sustainable remediation strategies for addressing DRN contamination.

Frustrated Lewis pairs created by Ce-doped Bi2MoO6: A universal strategy to promote efficient utilization of H2O2 for Fenton-like photodegradation.

Photo-Fenton-like technology based on H2O2 is considered as an ideal strategy to generate reactive oxygen species (ROS) for antibiotic degradation, but O2 overflow in the process severely limits the utilization efficiency of H2O2. Herein, we fabricate Bi2MoO6 (BMO) photocatalyst modified with Frustrated Lewis pairs (FLPs) as a Fenton catalyst model for enhancing reuse of spilled O2. The FLPs created by the introduction of cerium and oxygen vacancy were found to contribute to regulate the electronic structure of BMO and further improve the acidic and basic properties of photocatalyst surface. More importantly, the frustrated acid and base sites can enhance the H2O2 and O2 interfacial adsorption process and provide an Ce4+-Ov-O2- active site on the surface of Ce-BMO nanosheets, which can promote O2/•O2-/1O2/H2O2 redox cycles to achieve high H2O2 utilization efficiency. Specifically, in the experiment using tetracycline as a photocatalytic degradation object, the degradation activity of Ce-BMO was 2.15 times higher than that of BMO pure phase. Quenching experiments and EPR assays also confirmed that 1O2 and •O2- were the dominant oxidative species. This study systematically reveals the design of Fenton photocatalytic active sites at the atomic scale and provides new insights into constructing FLPs photocatalysts with high H2O2 utilization efficiency.

Dipole moment regulation for enhancing internal electric field in covalent organic frameworks photocatalysts.

Covalent organic frameworks (COFs) have recently emerged as a kind of promising photocatalytic platform in addressing the growing threat of trace pollutants in aquatic environments. Along this, we propose a strategy of constructing internal electric field (IEF) in COFs through the dipole moment regulation, which intrinsically facilitates the separation and transfer of photogenerated excitons. Two COFs of BTT-TZ-COF and BTT-TB-COF are developed by linking the electron-donor of benzotrithiophene (BTT) block and the electron-acceptor of triazine (TZ) or tribenzene (TB) block, respectively. DFT calculations demonstrate TZ block with larger dipole moment can achieve more efficient IEF due to the stronger electron-attractive force and hence narrower bandgap. Moreover, featuring the highly-order crystalline structure for accelerating photo-excitons transfer and rich porosity for facilitating the adsorption, BTT-TZ-COF exhibited an excellent universal performance of photocatalytic degradations of various dyes. Specifically, a superior photodegradation efficiency of 99% Rhodamine B (RhB) is achieved within 20 min under the simulated sunlight. Therefore, this convenient construction approach of enhanced IEF in COFs through rational regulation of the dipole moment can be a promising way to realize high photocatalytic activity.

Efficient photochemical conversion of naproxen by butanedione: Role of energy transfer.

Photochemical active species generated from photosensitizers, e.g., dissolved organic matter (DOM), play vital roles in the transformation of micropollutants in water. Here, butanedione (BD), a redox-active moiety in DOM and widely found in nature, was employed to photo-transform naproxen (NPX) with peracetic acid (PAA) and H2O2 as contrasts. The results obtained showed that the BD exhibited more applicable on NPX degradation. It works in the lake or river water under UV and solar irradiation, and its NPX degradation efficiency was 10-30 times faster than that of PAA and H2O2. The reason for the efficient transformation of pollutants is that the BD system was proved to be a non-free radical dominated mechanism. The quantum yield of BD (Ф254 nm) was calculated to be 0.064, which indicates that photophysical process is the dominant mode of BD conversion. By adding trapping agents, direct energy transfer from 3BD* to NPX (in anoxic environment) or dissolved oxygen (in aerobic environment) was proved to play a major role (> 91 %). Additionally, the BD process reduces the toxicity of NPX and promotes microbial growth after irradiation. Overall, this study significantly deepened the understanding of the transformation between BD and micropollutants, and provided a potential BD-based process for micropollutants removal under solar irradiation.

UV photo-degradation of the secondary lichen substance parietin: A multi-spectroscopic analysis in astrobiology perspective.

The cortical anthraquinone yellow-orange pigment parietin is a secondary lichen substance providing UV-shielding properties that is produced by several lichen species. In our work, the secondary metabolite has been extracted from air-dried thalli of Xanthoria parietina. The aims of this study were to characterize parietin absorbance through UV-VIS spectrophotometry and with IR spectroscopy and to evaluate its photodegradability under UV radiation through in situ reflectance IR spectroscopy to understand to what extent the substance may have a photoprotective role. This allows us to relate parietin photo-degradability to the lichen UV tolerance in its natural terrestrial habitat and in extreme environments relevant for astrobiology such as Mars. Extracted crystals were UV irradiated for 5.59 h under N2 flux. After the UV irradiation, we assessed relevant degradations in the 1614, 1227, 1202, 1160 and 755 cm-1 bands. However, in light of Xanthoria parietina survivability in extreme conditions such as space- and Mars-simulated ones, we highlight parietin UV photo-resistance and its relevance for astrobiology as photo-protective substance and possible bio-hint.

Central composite design and mechanism of antibiotic ciprofloxacin photodegradation under visible light by green hydrothermal synthesized cobalt-doped zinc oxide nanoparticles.

In this research, different Co2+ doped ZnO nanoparticles (NPs) were hydrothermally synthesized by an environmentally friendly, sustainable technique using the extract of P. capillacea for the first time. Co-ZnO was characterized and confirmed by FTIR, XPS, XRD, BET, EDX, SEM, TEM, DRS UV-Vis spectroscopy, and TGA analyses. Dislocation density, micro strains, lattice parameters and volume of the unit cell were measured using XRD results. XRD suggests that the average size of these NPs was between 44.49 and 65.69 nm with a hexagonal wurtzite structure. Tauc plot displayed that the optical energy bandgap of ZnO NPs (3.18) slowly declines with Co doping (2.96 eV). Near complete removal of the ciprofloxacin (CIPF) antibiotic was attained using Green 5% of Hy-Co-ZnO in the existence of visible LED light which exhibited maximum degradation efficiency (99%) within 120 min for 30 ppm CIPF initial concentration. The photodegradation mechanism of CIPF using Green Hy-Co-ZnO NPs followed the Pseudo-first-order kinetics. The Green Hy-Co-ZnO NPs improved photocatalytic performance toward CIPF for 3 cycles. The experiments were designed using the RSM (CCD) method for selected parameters such as catalyst dosage, antibiotic dosage, shaking speed, and pH. The maximal CIPF degradation efficiency (96.4%) was achieved under optimum conditions of 39.45 ppm CIPF dosage, 60.56 mg catalyst dosage, 177.33 rpm shaking speed and pH 7.57.

Light-induced degradation of dimethylmercury in different natural waters.

Photo-induced degradation of dimethylmercury (DMHg) is considered to be an important source for the generation of methylmercury (MMHg). However, studies on DMHg photodegradation are scarce, and it is even debatable about whether DMHg can be degraded in natural waters. Herein, we found that both DMHg and MMHg could be photodegraded in three natural waters collected from the Yellow River Delta, while in pure water only DMHg photodegradation occurred under visible light irradiation. The effects of different environmental factors on DMHg photodegradation were investigated, and the underlying mechanisms were elucidated by density functional theory calculations and a series of control experiments. Our findings revealed that the DMHg degradation rate was higher in the tidal creek water compared to Yellow River, Yan Lake, and purified water. NO3-, NO2-, and DOM could promote the photodegradation with DOM and NO3- showing particularly strong positive effects. Different light sources were employed, and UV light was found to be more effective in DMHg photodegradation. Moreover, MMHg was detected during the photodegradation of DMHg, confirming that the photochemical demethylation of DMHg is a source of MMHg in sunlit water. This work may provide a novel mechanistic insight into the DMHg photodegradation in natural waters and enrich the study of the global biogeochemical cycle of Hg.

Recent Developments in Porphyrin-Based Metal-Organic Framework Materials for Water Remediation under Visible-Light Irradiation.

Access to clean drinking water is a basic requirement, and eliminating pollutants from wastewater is important for saving water ecosystems. The porous structure and surface characteristics of metal-organic frameworks (MOFs) can function as a perfect scaffold for removing toxic compounds from wastewater. Porphyrins are promising building blocks for constructing MOFs. Porphyrin-based metal-organic frameworks (P-MOFs) have been fabricated using porphyrin ligands, metal clusters, or ions. These materials can harvest light from a wide region of the solar spectrum, and their framework morphology and physicochemical properties can be controlled by changing their peripheral subunits or metal ions. These porous crystalline materials have generated interest because of their distinctive characteristics, including large permanent porosity, interesting surface morphology, broad conformational diversity, high photostability, and semiconducting nature. This article discusses the recent progress and usefulness of P-MOFs. The fabrication procedures of P-MOFs are discussed, followed by the adsorptive and photocatalytic removal of contaminants from wastewater. The relationships between the geometries of P-MOFs and their light-harvesting and charge-transfer mechanisms for the photocatalytic degradation of pollutants are highlighted. Finally, some future perspectives and obstacles in the photodegradation usage of P-MOFs are discussed, along with feasible research directions to standardize efficient photocatalysts for improved photodegradation for water treatment.

Phase State Regulates Photochemical HONO Production from NaNO3/Dicarboxylic Acid Mixtures.

Field observations of daytime HONO source strengths have not been well explained by laboratory measurements and model predictions up until now. More efforts are urgently needed to fill the knowledge gaps concerning how environmental factors, especially relative humidity (RH), affect particulate nitrate photolysis. In this work, two critical attributes for atmospheric particles, i.e., phase state and bulk-phase acidity, both influenced by ambient RH, were focused to illuminate the key regulators for reactive nitrogen production from typical internally mixed systems, i.e., NaNO3 and dicarboxylic acid (DCA) mixtures. The dissolution of only few oxalic acid (OA) crystals resulted in a remarkable 50-fold increase in HONO production compared to pure nitrate photolysis at 85% RH. Furthermore, the HONO production rates (PHONO) increased by about 1 order of magnitude as RH rose from <5% to 95%, initially exhibiting an almost linear dependence on the amount of surface absorbed water and subsequently showing a substantial increase in PHONO once nitrate deliquescence occurred at approximately 75% RH. NaNO3/malonic acid (MA) and NaNO3/succinic acid (SA) mixtures exhibited similar phase state effects on the photochemical HONO production. These results offer a new perspective on how aerosol physicochemical properties influence particulate nitrate photolysis in the atmosphere.

Analytical method development, identification, and characterization of stress degradation products of idelalisib by ultrahigh-performance liquid chromatography with photodiode array and ultrahigh-performance liquid chromatography with electrospray ionization quadrupole time-of-flight mass spectrometry studies.

RATIONALE: As per International Council for Harmonization (ICH) drug stability test guideline Q1A(R2), inherent stability characteristics of a drug should be studied. This work was designed to investigate inherent degradation characteristics of the drug idelalisib under ICH prescribed stress conditions, identify its degradation products, and postulate their corresponding degradation pathways. METHODS: Idelalisib was subjected to the ICH prescribed conditions of hydrolytic (neutral, acidic, and alkaline), photolytic, oxidative, and thermal stress according to ICH guideline Q1A(R2). An ultrahigh-performance liquid chromatography with photodiode array (UHPLC-PDA) method was developed to adequately resolve the drug from its degradation products, validated as per the ICH guidelines, and subsequently extended to UHPLC with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOFMS) studies to identify the degradation products. RESULTS: Significant degradation was noted under conditions of acidic/alkaline hydrolysis, acid photolysis, and oxidative stress. The UHPLC/ESI-QTOFMS studies revealed the generation of four degradation products (I-IV), which were satisfactorily resolved from the drug by UHPLC on a Kinetex® C18 (100 × 4.6 mm; 2.6 µm) column by the developed isocratic elution method. Detection wavelength was selected as 270 nm. All the degradation products (I-IV) could be identified and characterized from their mass spectral data. The degradation pathways for the generation of various products from the drug were postulated. CONCLUSIONS: A UHPLC-PDA method was developed and validated for idelalisib. Four degradation products of idelalisib were revealed through UHPLC/ESI-QTOFMS studies, and corresponding degradation pathways were postulated for the same.

Simultaneous determination of folic acid photolysis products and oxidized guanine derivatives in plasma by liquid chromatography-tandem mass spectrometry.

Folic acid (FA) is easily photodegraded to yield 6-formylpterin and pterin-6-carboxylic acid, which can generate reactive oxygen species and result in the formation of oxidized guanine derivatives such as 8-hydroxy-2'-deoxyguanosine and 8-hydroxy-guanosine. In this study, we developed a simple, rapid, and sensitive liquid chromatography-tandem mass spectrometry strategy for the simultaneous determination of FA photolysis products and oxidized guanine derivatives in plasma samples. Chromatographic separation was performed on a Waters HSS T3 column (2.1 × 100 mm, 5.0 µm) with gradient elution at a flow rate of 0.25 mL/min. Plasma samples were first pretreated with 1% formic acid, followed by protein precipitation with methanol. The developed method showed good linear relationships between 1 and 2000 ng/mL (r2 > 0.99). The intra- and inter-day precisions ranged from 2.6% to 7.5% and from 2.5% to 6.5%, respectively. Recoveries of the analytes were between 75.4% and 112.4% with the relative standard deviation < 9.1%. Finally, the method was applied to quantify FA photolysis products and oxidized guanine derivatives in rats with light and non-light conditions.