分散液液微萃取/气相色谱-串联质谱法测定地表水中苯并三唑类紫外线过滤剂

建立了地表水中6种苯并三唑类紫外线过滤剂:2-(2-羟基-5-甲基苯基)苯并三唑(UV-P)、2-(5-叔丁基-2-羟苯基)苯并三唑(UV-PS)、2-(5-氯-2-苯并三唑)-6-叔丁基对甲酚(UV-326)、2-(3,5-二叔丁基-2-羟苯基)-5-氯苯并三唑(UV-327)、2-(3,5-二叔戊基-2-羟基苯基)苯并三唑(UV-328)及2-(2-羟基-5-叔辛基苯基)苯并三唑(UV-329)的分散液液微萃取/气相色谱-串联质谱分析方法。以50μL氯仿为萃取溶剂,600μL乙醇为分散溶剂,样品p H值为3.0。目标化合物经Rtx-5MS色谱柱结合程序升温分离后,用多重反应监测模式进行质谱分析,外标法定量。结果表明,6种化合物的基质加标回收率为83.5%~104.5%,相对标准偏差为5.1%~10.1%,方法的检出限为0.002~0.03μg/L,定量下限为0.008~0.1μg/L。     

超高效液相色谱-串联质谱法同时测定纺织品中4种苯并三唑类紫外稳定剂

建立了快速同时测定纺织品中UV-350,UV-320,UV-328和UV-327 4种苯并三唑类紫外稳定剂(BUVSs)的超声提取/超高效液相色谱-串联质谱(USE-UPLC-MS/MS)分析方法。样品经正己烷饱和的乙腈超声波提取后,采用Eclipse Plus C18柱(2.1 mm×50 mm,1.8μm)分离,甲醇-0.01 mol/L甲酸铵水溶液为流动相梯度洗脱,电喷雾离子源电离,正离子多反应监测模式进行定性和定量分析,外标法定量。结果表明,4种BUVSs的线性相关系数(r2)均大于0.99,检出限为0.006 3~0.024 mg/kg,定量下限为0.021~0.081 mg/kg。加标回收率为80.0%~102.9%,相对标准偏差(RSD)为1.2%~9.9%。将该方法应用于纺织品中BUVSs的分析测定,结果令人满意。     

Comparative Effect of UV,UV/H2O2 and UV/H2O2/Fe on Terbuthylazine Degradation in Natural and Ultrapure Water

Different advanced oxidation processes (AOPs) (ultraviolet radiation, hydrogen peroxide photolysis and photo-Fenton) were applied to test the degradation of terbuthylazine in three types of water: (a) ultrapure water, (b) surface water from the Gaditana area (Los Hurones reservoir, Cádiz, Spain) and (c) groundwater from the Tempul spring in Jerez de la Frontera (Cádiz, Spain). The experiments were carried out on a laboratory scale, using two different types of reactors, batch and semi-continuous. In batch reactors, the most efficient process for the experiments carried out with both ultrapure water and underground groundwater was ultraviolet radiation, whereas for surface water from the Gaditana area, the process that obtained the best results was the photolysis of hydrogen peroxide with 2.5 mg L⁻¹ of H₂O₂. In semi-continuous reactors, the most efficient process was the photolysis of hydrogen peroxide with 2.5 mg L⁻¹ of H₂O₂ for all the matrices studied. In both types of reactors, terbuthylazine degradation percentages higher than 90% were achieved; the main difference was in the reaction time, which varied from minutes in the batch reactor to seconds in the semi-continuous reactor. In all the applied AOPs, N-terbutyl-6-hydroxy-N′ethyl-1,3,5-triazine-2,4-diamine (TBA-212) was generated as a reaction intermediate.     

Atrazine and Parathion-Methyl Removal by UV And UV/O3 in Drinking Water Treatment

Abstract

The degradation of atrazine and parathion-methyl by UV-light in the presence of O₂(UV/O₂) and by a combination of UV-light and ozone in the presence of O₂(UV/O₂/O₃) was studied at a pilot plant for drinking water treatment. The photolysis rate of parathion-methyl increased with UV/O₂/O₃ compared to the treatment with UV/O₂ only, while the photodecomposition rate of atrazine was not enhanced by the UV/O₂/O₃ combination under the working conditions applied.

In field experiments with a large-scale plant the degradation of atrazine and desethylatrazine was studied at a drinking water supply. The applied ozone dose rates were smaller and the residence time of the liquid phase in the UV-reaction unit was shorter than in the pilot plant. The degradation rate of both atrazine and desethylatrazine increased with increasing ozone dose rates and increasing radiant power. At a continuous flow rate of 70 m³/h of contaminated raw water atrazine could be degraded below the threshold limit for pesticides (0.1[ugrave]g/L) at optimum operation conditions, whereas the resulting desethylatrazine concentration exceeded this limit. At a continuous flow rate of 30 m³/h desethylatrazine could be degraded below the threshold limit, too.     

Polyaniline Modified CNTs and Graphene Nanocomposite for Removal of Lead and Zinc Metal Ions: Kinetics,Thermodynamics and Desorption Studies

A novel polyaniline-modified CNT and graphene-based nanocomposite (2.32–7.34 nm) was prepared and characterized by spectroscopic methods. The specific surface area was 176 m²/g with 0.232 cm³/g as the specific pore volume. The nanocomposite was used to remove zinc and lead metal ions from water; showing a high removal capacity of 346 and 581 mg/g at pH 6.5. The data followed pseudo-second-order, intraparticle diffusion and Elovich models. Besides this, the experimental values obeyed Langmuir and Temkin isotherms. The results confirmed that the removal of lead and zinc ions occurred in a mixed mode, that is, diffusion absorption and ion exchange between the heterogeneous surface of the sorbent containing active adsorption centers and the solution containing metal ions. The enthalpy values were 149.9 and 158.6 J.mol⁻¹K⁻¹ for zinc and lead metal ions. The negative values of free energies were in the range of −4.97 to −26.3 kJ/mol. These values indicated an endothermic spontaneous removal of metal ions from water. The reported method is useful to remove the zinc and lead metal ions in any water body due to the high removal capacity of nanocomposite at natural pH of 6.5. Moreover, a low dose of 0.005 g per 30 mL made this method economical. Furthermore, a low contact time of 15 min made this method applicable to the removal of the reported metal ions from water in a short time. Briefly, the reported method is highly economical, nature-friendly and fast and can be used to remove the reported metal ions from any water resource.     

Reactivity of 3‐Methylbenzenediazonium Ions with Gallic Acid. Kinetics and Mechanism of the Reaction

We investigated the kinetics and mechanism of the reaction between the 3‐methylbenzenediazonium ions (3MBD), and gallic acids (=3,4,5‐trihydroxybenzoic acid; GA) in aqueous buffer solution under acidic conditions by employing spectrometric, electrochemical, and chromatographic techniques and computational methods. To discern which of the three OH groups of GA is the first one undergoing deprotonation, the geometries of the resulting dianions were optimized by using B3LYP hybrid density‐functional theory (DFT) and a 6‐31G(++d,p) basis set, and the results suggest that the OH group at the 4‐position is the first one which is deprotonated. The variation of the observed rate constant, k_obs, with the acidity at a given [GA] follows an upward curve suggesting that the reaction takes place with the dianionic form of gallic acid, GA^2?, and rate enhancements of ca. 23000 fold are obtained on going from pH 3.5 up to pH 7.5. At relatively high acidities, the variation of k_obs with [GA] is linear with an intercept very close to the value for the thermal decomposition of 3MBD; however, a decrease in the acidity leads to saturation‐kinetics profiles with nonzero, pH‐dependent intercepts. The saturation‐kinetics patterns found suggest the formation of an intermediate in a rapid pre‐equilibrium step, but the nonzero, pH‐dependent intercepts cause the double reciprocal plots of 1/k_obs vs. 1/[GA] to curve. This prompts us to propose an alternative reaction mechanism comprising consecutive equilibrium processes involving the bimolecular, reversible formation of a highly unstable (Z)‐diazo ether which undergoes isomerization to the (E)‐isomer through a unimolecular step. The results obtained indicate the complexity of reactions of arenediazonium ions with nucleophilic arenes containing three or more OH groups.     

Electrochemiluminescence of Carbon-based Quantum Dots: Synthesis,Mechanism and Application in Heavy Metal Ions Detection

In recent years, carbon-based quantum dots as luminophores and co-reactants have aroused broad interest for their ability to function in electrochemiluminescence (ECL) sensors due to their unique features, including excellent biocompatibility, low toxicity, and water solubility. In this mini review, the synthesis methods of carbon-based quantum dots are firstly introduced. Then, the mechanism of carbon-based quantum dots as luminophores and co-reactants and their latest progress application in the detection of heavy metal ions are explored. Finally, the current challenges and potential future development directions of carbon-based quantum dots in ECL sensing filed for heavy metal ions analysis are summarized.     

Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy

Iron catalysts have been used widely for the mass production of carbon nanotubes (CNTs) with high yield. In this study, UV/visible spectroscopy was used to determine the Fe catalyst content in CNTs using a colorimetric technique. Fe ions in solution form red–orange complexes with 1,10-phenanthroline, producing an absorption peak at λ=510 nm, the intensity of which is proportional to the solution Fe concentration. A series of standard Fe solutions were formulated to establish the relationship between optical absorbance and Fe concentration. Many Fe catalysts were microscopically observed to be encased by graphitic layers, thus preventing their extraction. Fe catalyst dissolution from CNTs was investigated with various single and mixed acids, and Fe concentration was found to be highest with CNTs being held at reflux in HClO₄/HNO₃ and H₂SO₄/HNO₃ mixtures. This novel colorimetric method to measure Fe concentrations by UV/Vis spectroscopy was validated by inductively coupled plasma optical emission spectroscopy, indicating its reliability and applicability to asses Fe content in CNTs.     

高效液相色谱-电喷雾串联质谱法对氧化条件下缬草素降解产物的结构及氧化动力学研究

建立了评价缬草素在氧化条件下稳定性的系统方法。采用高效液相色谱-电喷雾串联质谱(HPLC-ESI MS/MS)法对缬草素在氧化条件下(H2O2)的降解产物进行分离,并对主要降解产物进行结构鉴定,样品经Agilent Extend-C18分离,以乙腈-0.25%乙酸水溶液为流动相,梯度洗脱,质谱条件为电喷雾离子源(ESI),正离子模式检测。在上述条件下,共鉴定出4个主要降解产物,其中1个由标准品对照而得,4个化合物的结构母核均为缬草醛类成分。利用HPLC测定缬草素在H2O2中不同时间点的含量变化,经计算缬草素在H2O2中的变化符合一级动力学方程,10%的原型产物发生降解的时间为0.5 h。实验从定性和定量两方面揭示了缬草素的降解机制和降解规律,可为缬草素或含有缬草素的中药制剂的进一步研究与应用提供依据。     

Removal and mineralization of toluene under VUV/UV lamp irradiation in humid air: Effect of light wavelength,O2 and H2O

VUV/UV photodegradation is a promising method that utilizes energetic photons and reactive oxygen species (ROS) generated via the photo-dissociation of H₂O and O₂ to degrade VOCs. In the paper, we investigated the efficiency of removal and mineralization in humid air and the effects of key factors. Toluene of 4–20 ppm can be almost completely removed in 60 s and mineralization efficiency is above 55% at 25 min. 185 nm ultraviolet light plays a key role in the rapid removal and mineralization of toluene. Appropriate amount of O₂ and H₂O promote the removal of toluene due to the generation of ROS. Based on the intermediates and degradation pathway analysis, it is found that in the presence of O₂, degradation pathways of toluene are more abundant and fewer linear-chain aldehydes are produced, thus resulting in higher mineralization efficiency. This work highlights the importance of practical application of VUV/UV photodegradation in humid air.     

Cost‐Efficient Graphitic Carbon Nitride as an Effective Photocatalyst for Antibiotic Degradation: An Insight into the Effects of Different Precursors and Coexisting Ions,and Photocatalytic Mechanism

In this study, the photocatalytic activity of graphitic carbon nitride (g‐C₃N₄) synthesized via different precursors (urea, thiourea, and dicyandiamide) is investigated in the degradation process of tetracycline. Owing to the efficient charge separation and transfer, prolonged radiative lifetime of charge, large surface area, and nanosheet morphology, the urea‐derived g‐C₃N₄ exhibits superior photocatalytic activity for tetracycline degradation under visible‐light irradiation. This performance can compare with that of most reported g‐C₃N₄‐based composite photocatalysts. Through the time‐circle degradation experiment, the urea‐derived g‐C₃N₄ is found to have an excellent photocatalytic stability. The presence of NO₃^?, CH₃COO^?, Cl^? and SO₄^2? ions with the concentration of 10 mm inhibits the photocatalytic activity of urea‐derived g‐C₃N₄, where this inhibitory effect is more obvious for Cl^? and SO₄^2? ions. For the coexisting Cu²⁺, Ca²⁺, and Zn²⁺ ions, the Cu²⁺ ion exhibits a significantly higher inhibitory effect than Ca²⁺ and Zn²⁺ ions for tetracycline degradation. However, both the inhibitory and facilitating effects are observed in the presence of Fe³⁺ ion with different concentration. The h⁺, ^.OH and ^.O₂^? radicals are confirmed as major oxidation species and a possible photocatalytic mechanism is proposed in a urea‐derived g‐C₃N₄ reaction system. This study is of important significance to promote the large‐scale application of g‐C₃N₄ photocatalysts in antibiotic wastewater purification.     

Degradation of Carbon Tetrachloride by nanoscale Zero‐Valent Iron @ magnetic Fe3O4: Impact of reaction condition,Kinetics, Thermodynamics and Mechanism

Nano‐scale zero‐valent Iron (nZVI) attached on the Fe₃O₄ nanoparticles were prepared and creatively applied in the reductive dechlorination of Carbon Tetrachloride (CT). The characterization results of the synthesized composite indicated a main component of nZVI particles assembled on the surface of Fe₃O₄ with a layer of iron‐oxide film on the periphery, of which the dispersibility was better and the specific surface area was larger. The effects of different reaction conditions like temperature, initial pH values, Fe⁰@Fe₃O₄ dosage and initial CT concentrations on the removal of CT were evaluated. Under the optimum conditions, the Fe⁰@Fe₃O₄ composites showed a CT removal efficiency of 89.1% in 60 min, which was much greater than that of nZVI (61.7%) and Fe₃O₄ particles (14.3%). The removal process obeyed the pseudo‐first‐order kinetic model. Synergy effects of the constituents in the composite which can promote the relative rates of mass transfer to reactive sites were proposed to be existed and the magnetism of Fe₃O₄ could help to overcome the aggregation and surface passivation problem of nZVI. Thus, Fe⁰@Fe₃O₄ nanoparticles in our study can effectively complete the reductive dechlorination of CT and an improved nZVI catalyst is provided for the remediation of chlorinated organic compounds.     

Infrared study of νOD modes in isotopically dilute (HDO) isostructural compounds M(HCOO)2·2H2O (M=Mn,Fe,Co,Ni,Cu,Zn) with matrix-isolated guest ions (Cu in M(HCOO)2·2H2O and M in Cu(HCOO)2·2H2O)

The infrared spectra of isotopically dilute (matrix-isolated HDO molecules) isostructural compounds M(HCOO)₂·2H₂O (M=Mn,Fe,Co,Ni,Zn,Cu) are presented and discussed in the region of the OD stretching modes. According to the structural data the compounds under study are divided into two groups: in M(HCOO)₂·2H₂O (M=Mn,Ni,Zn) the H₂O(1) molecules form stronger hydrogen bonds as compared to H₂O(2); in M(HCOO)₂·2H₂O (M=Fe,Co,Cu) the H₂O(2) molecules form stronger hydrogen bonds as compared to the H₂O(1) molecules. The influence of the metal–water interactions (synergetic effect) and the unit-cell volumes (repulsion potential of the lattice) on the hydrogen bond strength within the isostructural series is discussed. The wavenumbers of the uncoupled OD stretching modes of the HDO molecules influenced by guest ions (Cu²⁺ ions matrix-isolated in M(HCOO)₂·2H₂O and M²⁺ ions matrix-isolated in Cu(HCOO)₂·2H₂O) are presented and commented. For example, the analysis of the spectra reveals that when Cu²⁺ ions are included in the structure of M(HCOO)₂·2H₂O the hydrogen bonds of the type M–OH₂OCHO–Cu are considerably weaker as compared to those of the same type formed when M²⁺ ions are included in the structure of Cu(HCOO)₂·2H₂O if the cations remain unchanged.     

Oleogel Formulations for the Topical Delivery of Betulin and Lupeol in Skin Injuries—Preparation,Physicochemical Characterization,and Pharmaco-Toxicological Evaluation

The skin integrity is essential due to its pivotal role as a biological barrier against external noxious factors. Pentacyclic triterpenes stand as valuable plant-derived natural compounds in the treatment of skin injuries due to their anti-inflammatory, antioxidant, antimicrobial, and healing properties. Consequently, the primary aim of the current investigation was the development as well as the physicochemical and pharmaco-toxicological characterization of betulin- and lupeol-based oleogels (Bet OG and Lup OG) for topical application in skin injuries. The results revealed suitable pH as well as organoleptic, rheological, and textural properties. The penetration and permeation of Bet and Lup oleogels through porcine ear skin as well as the retention of both oleogels in the skin were demonstrated through ex vivo studies. In vitro, Bet OG and Lup OG showed good biocompatibility on HaCaT human immortalized cells. Moreover, Bet OG exerted a potent wound-healing property by stimulating the migration of the HaCaT cells. The in ovo results demonstrated the non-irritative potential of the developed formulations. Additionally, the undertaken in vivo investigation indicated a positive effect of oleogels treatment on skin parameters by increasing skin hydration and decreasing erythema. In conclusion, oleogel formulations are ideal for the local delivery of betulin and lupeol in skin disorders.     

Hydroxycinnamic Acids as DNA‐Cleaving Agents in the Presence of CuII Ions: Mechanism,Structure–Activity Relationship,and Biological Implications

The effectiveness of hydroxycinnamic acids (HCAs), that is, caffeic acid (CaA), chlorogenic acid (ChA), sinapic acid (SA), ferulic acid (FA), 3‐hydroxycinnamic acid (3‐HCA), and 4‐hydroxycinnamic acid (4‐HCA), as pBR322 plasmid DNA‐cleaving agents in the presence of Cu^II ions was investigated. Compounds bearing o‐hydroxy or 3,5‐dimethoxy groups on phenolic rings (CaA, SA, and ChA) were remarkably more effective at causing DNA damage than the compounds bearing no such groups; furthermore, CaA was the most active among the HCAs examined. The involvement of reactive oxygen species (ROS) and Cu^I ions in the DNA damage was affirmed by the inhibition of the DNA breakage by using specific scavengers of ROS and a Cu^I chelator. The interaction between CaA and Cu^II ions and the influence of ethylenediaminetetraacetic acid (EDTA), the solvent, and pH value on the interaction were also studied to help elucidate the detailed prooxidant mechanism by using UV/Vis spectroscopic analysis. On the basis of these observations, it is proposed that it is the CaA phenolate anion, instead of the parent molecule, that chelates with the Cu^II ion as a bidentate ligand, hence facilitating the intramolecular electron transfer to form the corresponding CaA semiquinone radical intermediate. The latter undergoes a second electron transfer with oxygen to form the corresponding o‐quinone and a superoxide, which play a pivotal role in the DNA damage. The intermediacy of the semiquinone radical was supported by isolation of its dimer from the Cu^II‐mediated oxidation products. Intriguingly, CaA was also the most cytotoxic compound among the HCAs toward human promyelocytic leukemia (HL‐60) cell proliferation. Addition of exogenous Cu^II ions resulted in an effect dichotomy on cell viability depending on the concentration of CaA; that is, low concentrations of CaA enhanced the cell viability and, conversely, high concentrations of CaA almost completely inhibited the cell proliferation. On the other hand, when superoxide dismutase was added before, the two stimulation effects of exogenous Cu^II ions were significantly ameliorated, thus clearly indicating that the oxidative‐stress level regulates cell proliferation and death. These findings provide direct evidence for the antioxidant/prooxidant mechanism of cancer chemoprevention.     

Degradation of carbon tetrachloride using ultrasound‐assisted nanoscaled zero‐valent iron particles@sulfur/nitrogen dual‐doped reduced graphene oxide composite: Kinetics,activation energy,effects of reaction conditions and degradation mechanism

We report a study of the synthesis of nanoscale zero‐valent iron particles stabilized by sulfur/nitrogen dual‐doped reduced graphene oxide (i.e. nZVI@SN‐rGO) and their applications as major reactants for the dechlorination of carbon tetrachloride (CT) by combining sonolysis with consideration of several operation parameters such as pH, temperature, catalyst dosage, as well as in the presence of common inorganic anions. The experimental results showed that the modified technology could remain effective for up to 180 min of reaction time under optimal conditions. Especially, there was no significant reduction in the removal efficiency toward CT even after five cycles, which was indicative of good stability. A study of the effects of common inorganic anions revealed that the presence of Clˉ and HCO₃ˉ exhibited different positive effects in the following order: Clˉ > HCO₃ˉ; NO₃ˉ and SO₄²ˉ showed inhibition effects on CT removal. The structure and properties of nZVI@SN‐rGO were characterized using X‐ray diffraction, scanning electron microscopy, surface area analysis, Raman spectroscopy and X‐ray photoelectron spectroscopy. Additionally, the corresponding activation energy was approximately 31.04 kJ mol^?1, suggesting that the surface chemical reaction rather than diffusion was the rate‐limiting step in the CT decomposition process. More importantly, the possible reaction mechanism and dechlorination pathway of CT using the ultrasound‐assisted nZVI@SN‐rGO system were also investigated.     

Proton/Hydrogen‐Transfer Coordinate of 2,5‐Dihydroxybenzoic Acid Investigated in a Supersonic Beam: Combined IR/UV Spectroscopy in the S0, S1, and D0 States

As a model system for intramolecular proton/hydrogen‐transfer coordinates, the structure of 2,5‐dihydroxybenzoic acid is investigated for the ground, first electronically excited and also the ionic state. Combined IR/UV spectroscopy in molecular‐beam experiments is applied and the experimental results are interpreted by the application of DFT and CASPT2 methods. No proton or hydrogen transfer is observed, but evidence is given for a hydrogen dislocation of the intramolecular hydrogen bond in the S₁ state and to lesser extent in the D₀ state. To obtain direct information on the proton/hydrogen‐transfer coordinate, IR spectra are recorded both in the region of the OH and especially the CO stretching vibrations by also applying two new variants of combined IR/UV spectroscopy for the S₁ and D₀ states. The CO groups are directly involved in the hydrogen bond and, in contrast to the hydrogen‐bonded OH groups, the CO stretching frequencies can be observed in all electronic states.     

Determination of methanol in o,o-dimethyldithiophosphoric acid (DMDTPA) of technical grade by UV/vis spectrophotometry and by HPLC

Two procedures are proposed in this work for the determination of methanol impurities in o,o-dimethyldithiophosphoric acid (DMDTPA). To avoid possible interferences from the main component, DMDTPA was precipitated in the form of insoluble lead complex. Free Pb(II) ions were eliminated with sulfuric acid and methanol was oxidized to formaldehyde with potassium permanganate in methanesulfonic acid medium. Finally, the excess of oxidizing agent was neutralized with saturated sodium oxalate. The above pretreatment procedure was identical for spectrophotometric assay and for chromatographic determination. In the first case, the solution obtained was treated with Nash reagent to form 3,5-diacetyl-1,4-dihydrolutidine (λ_max = 415 nm). In the calibration range 0.1-1.0% (methanol in DMDTPA), the analytical figures of merit were: R² = 0.9993, quantification limit 0.02% methanol in DMDTPA coefficient of variance (n = 5) for 0.1% and 0.4% methanol respectively 6.7% and 2.4%. Recoveries obtained in the sample fortified with 0.1, 0.2, 0.4% of methanol (in DMDTPA) were in the range 99-105%. For chromatographic procedure, formaldehyde was derivatized with 2,4-dinitrophenylhydrazine and separation was achieved on Luna C18(2) column using the isocratic elution with acetonitrile-water (70:30, v/v) and spectrophotometric detection at 360 nm. In the calibration range 0.05-0.25% (methanol in DMDTPA), R² was always higher than 0.999, the quantification limit was 0.004% and the recoveries in these same fortified samples in the range 98-101%. No statistically significant differences were observed between the results obtained in the analysis of technical grade DMDTPA by the two procedures (ANOVA, p < 0.05)