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Polychlorinated naphthalenes (PCNs) have a structure similar to that of polychlorinated biphenyls (PCBs) and represent a new type of persistent organic pollutants (POPs) that are widely present in the environment and biological communities. PCNs can migrate and transform via different environmental media, which severely affects the health of humans and organisms. Researchers have devoted considerable focus on ambient air pollution. Although the current ambient air quality has not yet limited the concentration of PCNs, the Stockholm Convention has required parties to prohibit and eliminate their production and use. As one of the contracting parties, China is obligated to improve its environmental monitoring. In other words, the development of a method for monitoring PCNs in ambient air is important for understanding ambient air quality and safeguarding human health. PCNs are generally present at trace levels (pg/m

Abstract: A broad class of dihydroxyarenes were easily oxidized by aerobic oxygen to quinone products in excellent yields under the catalytic effect of polymer-supported RuII-Pheox/silica-gel catalyst. By using this combined catalyst, hydroquinone and catechol derivatives with electron-donating groups were easily oxidized by molecular oxygen to quinone products in 90% to >99% yield, while in the case of electron-withdrawing group, only 70% was obtained. The biologically useful 1,4-Naphthoqinone products were obtained in 83% to 90%. The catalyst was easily obtained and reused many times without a significant decrease in reactivity. Interestingly, a sample of industrial water contaminated with phenolic compounds was subjected to aerobic oxidation by using this catalyst, and the resultant quinones were detected within one day and the catalyst was removed and reused several times with different contaminating samples with the same efficiency. Other catalytic oxidations by using this promising catalyst were investigated.

With the ever-evolving cannabis industry, low-cost and high-throughput analytical methods for cannabinoids are urgently needed. Normally, (potentially) psychoactive cannabinoids, typically represented by Δ9-tetrahydrocannabinol (Δ9-THC), and nonpsychoactive cannabinoids with therapeutic benefits, typically represented by cannabidiol (CBD), are the target analytes. Structurally, the former (tetrahydrocannabinolic acid (THCA), cannabinol (CBN), and THC) have one olefinic double bond and the latter (cannabidiolic acid (CBDA), cannabigerol (CBG), and CBD) have two, which results in different affinities toward Ag(I) ions. Thus, a silica gel thin-layer chromatography (TLC) plate with the lower third impregnated with Ag(I) ions enabled within minutes a digital chromatographic separation of strongly retained CBD analogues and poorly retained THC analogues. The resolution (Rs) between the closest two spots from the two groups was 4.7, which is almost 8 times higher than the resolution on unmodified TLC. After applying Fast Blue BB as a chromogenic reagent, smartphone-based color analysis enabled semiquantification of the total percentage of THC analogues (with a limit of detection (LOD) of 11 ng for THC, 54 ng for CBN, and 50 ng for THCA when the loaded volume is 1.0 μL). The method was validated by analyzing mixed cannabis extracts and cannabis extracts. The results correlated with those of high-performance liquid chromatography with ultraviolet detection (HPLC-UV) (R2 = 0.97), but the TLC approach had the advantages of multi-minute analysis time, high throughput, low solvent consumption, portability, and ease of interpretation. In a desiccator, Ag(I)-TLC plates can be stored for at least 3 months. Therefore, this method would allow rapid distinction between high and low THC varieties of cannabis, with the potential for on-site applicability.

We present the green, highly atom-economical, solid-state silica gel-catalyzed synthesis of polysubstituted 1,4- and 1,2-dihydropyridines (DHPs) from commercially available materials, amines and ethyl propiolate. The DHP skeleton was assembled by heating the reactants and silica gel in a closed vessel. Aliphatic amines provided 1,4-isomers as the main or only DHP products, but the reactions of aromatic amines yielded a mixture of 1,4- and 1,2-isomers. To the best of our knowledge, this is the first example of the formation of a 1,2-DHP structure by the reaction of an amine with propiolic ester. Addition of 1 mass percent of H2SO4 to silica gel shifted the product distribution to 1,4-DHP as the main or the only isomer obtained. Experimental and theoretical analyses led to the identification of two key intermediates en route to DHPs and the explanation of the observed regioisomeric ratios. 1,2-DHPs show blue-cyan fluorescence in MeOH with the quantum yield Φ = 0.10–0.22 relative to quinine sulfate Φ = 0.58 and 1,4-DHPs show blue-violet fluorescence with Φ = 0.09–0.81. Supplementary material: [https://cherry.chem.bg.ac.rs/handle/123456789/5846]

The ion-exchange behavior of an organomineral material with an imidazolium (1-methyl-3-(prop-2-yn-1-yl)-1H-imidazol-3-ium bromide)-modified silica gel was studied for the extraction of Ag(I) from nitric acid media. The extraction from multicomponent systems containing Fe(III), Co(II), Ni(II), Cu(II), Pb(II), and Mn(II) in 100- and 1000-fold molar excesses with respect to Ag(I) was shown to occur with high selectivity. Based on the data of X-ray diffraction and X-ray fluorescence spectroscopy for samples of modified silica gel, a mixed ion exchange–adsorption mechanism for the extraction of Ag(I) was proposed. The effect of the phase contact time and the concentration of nitric acid on the distribution coefficient of Ag(I) was studied. The selectivity factors of the extraction of Ag(I) from multicomponent systems containing foreign cations in 100- and 1000-fold molar excesses under steady-state and dynamic concentration conditions were calculated.

Formaldehyde is a dangerous chemical present in many industrial waste gases. It can be recovered via catalytic processes; however, many of these require costly precious metals operating under limited reaction temperatures, making their industrialization difficult. This paper proposes a novel method of formaldehyde recovery. A sulfonation catalyst is used to promote a condensation reaction of methanol and formaldehyde to form methylal. Hence, a valuable chemical product is obtained while removing formaldehyde. A series of Al2O3-xSO3H catalysts were designed and the effects of surface acidity and hydroxyl groups on catalytic activity were explored by varying the activation temperature and sulfonation ratio. At an activation temperature of 60 °C, the yield of formaldehyde reaches 78.62% and the selectivity to methylal reaches 80.11%. This recovery rate is much higher than those reported in other studies. Through a series of characterizations, it was found that when the content of –SO3H groups is low, the hydroxyl content increases, which provides more activation centers for the formation of by-product formic acid from formaldehyde, and for the dehydration and condensation of formic acid and methanol to form methyl formate. At the same time, when the content of –SO3H groups is too high, side reactions of methanol and formaldehyde occur preferentially. Therefore, the synergistic effect of the contents of –SO3H and hydroxyl groups is the fundamental cause of the excellent catalytic performance. Based on in-situ infrared research, a possible mechanism of the reaction between methanol and formaldehyde on sulfonated silica gel is proposed, which also verifies the characterization of the catalyst. This research presents new possibilities for solving the problem of formaldehyde pollution.

Herein, a facile bottom–up approach for producing nitrogen-doped carbon quantum dots (N-CQDs) was carried out by the hydrothermal treatment of microcrystalline cellulose, in the presence of different nitrogen sources (blank/urea/ammonia water/ethanediamine(EDA)/Hexamethylenetetramine). The result showed that the fluorescence intensity and quantum yields (QYs) of N-CQDs with different nitrogen sources are all higher than that without nitrogen source. Compared with the other three nitrogen sources, N-CQDs prepared by EDA not only have the highest fluorescence intensity but also the largest QYs of 51.39%. Therefore, EDA was chosen as the nitrogen source to prepare N-CQDs. The obtained N-CQDs are uniform spherical particles with a diameter of 2.76 nm. The N-CQDs also exhibit excitation-dependent and long-wave emission properties. The emission range of N-CQDs is 470–540 nm. Moreover, N-CQDs as fluorescent agents successfully acted on purple LEDs (λem = 365 nm) to achieve white LEDs light emission. At the same time, a fluorescent thin layer chromatography plate was successfully prepared using N-CQDs, silica gel G and Sodium carboxymethylcellulose as raw materials. The separation trajectory of mixed sample of Sudan red III and kerosene on the fluorescent TLC plate is obviously clearer than that of the TLC plate.

A family of axially chiral azepine-containing seven-membered cyclic P,N-ligands (named Indole-azepinap) have been prepared by using l-alanine as an original chirality source. The direct chromatographic separation of two diastereomeric phosphine oxides on silica gel enabled these ligands to be easy available, allowing further structural and electronic modifications. Preliminary application of these Indole-azepinaps has been demonstrated in a Pd-catalyzed asymmetric allylic alkylation with high yields and moderate enantioselectivities.

The catalytic activity of a base metal-terpyridine complex immobilized on silica gel (M(tpy)X2 @SiO2 /H2 O: M=Mn, Fe, Co, Ni, Cu; X=Cl, Br) for hydrosilylation was investigated. Co(tpy)Br2 @SiO2 /H2 O in the presence of NaBHEt3 exhibited the highest catalytic activity for hydrosilylation of 1-octene with diphenylsilane (Ph2 SiH2 ) to form the anti-Markovnikov-type hydrosilylation compound as the main product. The reusability of Co(tpy)Br2 @SiO2 /H2 O activated by NaBHEt3 was examined. It was found that the catalytic activity decreased with repeated use because of the peeling off of the Co complex anchor portion from the silica gel surface upon the attack of NaBHEt3 . The introduction of Co(OAc)2 instead of CoBr2 to silica gel formed Co(tpy)(OAc)2 - and Co(tpy)(OH)2 -immobilized silica gel, which exhibited catalytic activity for the hydrosilylation in the absence of an activator such as NaBHEt3 . The glassware in which Co(tpy)(OH)2 was immobilized on the inner wall was prepared. It was found that the hydrosilylation catalytically occurred on the surface of a pretreated glassware and that the catalytic activity did not decrease even after 10 repeated uses.

Emerging pollutants (EPs) are chemical substances that are commonly not regulated and can be detected at low or very low concentrations. However, EPs have triggered special concern because their long-term adverse effects on the environment and human health remain unknown. Most EPs show biological toxicity, environmental persistence, and bioaccumulation. Even at low concentrations in the environment, EPs may pose significant environmental and health risks. Therefore, their treatment has been explicitly included in the 14th Five Year Plan for National Economic and Social Development of the People's Republic of China and the Outline of the Long-term Goals for 2035. Soil is a source of pollutants, and its quality is directly related to economic development, ecological security, and people's livelihood. At present, China's soil environmental monitoring system is not perfect, and the ability to monitor these new organic pollutants is lagging. Therefore, to strengthen the supervision of construction and agricultural land soil environments, it is essential to strengthen the soil environment monitoring ability for these EPs and establish a reliable, steady, and economic analysis method, including their separation and analysis methods in soil. Polychlorinated naphthalenes (PCNs) have received considerable attention as emerging halogenated compounds. They were listed in Annexes A and C of the Stockholm Convention on persistent organic pollutants (POPs) in 2015 because of their persistence, multimedia fate, and toxicity. PCNs have now been detected in the surrounding soils. Owing to their trace levels in complex soil, high requirements have been put forward for the pretreatment and instrument analysis of PCNs. This study aims to develop a new method for the selective purification of PCNs in soil, which can not only effectively remove lipids and other interferences in soil but also effectively reduce time, labor, and material costs in the pre-treatment process. Based on the physicochemical properties of the 13X molecular sieve, it was explored to purify soil-extracts as solid-phase extraction (SPE) sorbents. With n-hexane as the loading and rinsing solvent, 10 mL of a dichloromethane/n-hexane mixture (2∶15, v/v) was used to elute the PCNs. Moreover, selective separation of target substances from lipid macromolecules and other interferences could be achieved simultaneously. For the selective separation of PCNs, the average recovery of the internal standard could reach 56.1% to 88.0%. 13X molecular sieves are superior to gel permeation chromatography (GPC) and Florisil SPE, and they exhibit good cleanup efficiency similar to a multilayer silica gel/alumina column (53.0%-117.0%). Although the obtained recoveries are not as high as those obtained with a multilayer silica gel/alumina column, 13X molecular sieves have advantages in terms of simple operation, environmental friendliness, and low cost. Based on these fundamental experiments, accelerated solvent extraction was used to extract targets in soil, molecular sieves were used as SPE sorbents for purification, and GC-MS/MS was employed for PCN analysis. This method was developed as a systematic analytical method for PCNs determination. The method detection limits (MDLs) for PCN homologs were in the range of 0.009-0.6 ng/g. The precision and accuracy of the method were evaluated using spiked matrices. At three spiked levels (4, 10, and 18 ng), the recoveries of PCNs (CN-3, 13, 42, 46, 52, 53, 73, and 75) were 70%-128%, 71%-115%, and 61%-114%, respectively, and the corresponding relative standard derivations were 4.2%-23%, 6.5%-31% and 4.7%-22%. Thus, this method meets the requirements of trace analysis and shows acceptable parallelism, sensitivity, accuracy, and precision, thus being feasible for the analysis of emerging pollutant. The method is expected to play an important role in sample pretreatment in the future, especially for the nationwide investigation of soil pollution.

The NIS synthetase family of enzymes responsible for the biosynthesis of siderophores is increasingly associated with bacterial virulence. Proteins in this class represent outstanding potential drug targets, assuming that basic biochemical and structural characterizations can be completed. Towards this goal, we have mated an improved synthesis of the non-commercial amino acid N-hydroxy-N-succinylcadaverine (HSC, 6) with an isothermal titration calorimetry (ITC) assay that profiles the iterative stages of HSC trimerization and macrocyclization by NIS synthetase DesD from Streptomyces coelicolor. HSC synthesis begins with multigram-scale Gabrielle and tert-butyl N-(benzyloxy)carbamate alkylations of 1-bromo-5-chloropentane following prior literature, but the end-game reported herein has two advantages for greater material throughput: (1) hydrogenolysis of benzyl ether and Cbz blocking groups is best accomplished with Pearlman’s catalyst at 40 psi of H2 and (2) purification of neutral (zwitterionic) HSC is effected by simple flash chromatography over silica gel in MeOH. HSC is subsequently shown to be a substrate for NIS synthetase DesD, which catalyzes three successive amide bond syntheses via adenyl monophosphate ester intermediates. We quantify and present the iterative and overall enzyme kinetic constants associated with formation of the cyclotrimeric siderophore desferrioxamine E (dfoE, 1).

The plants Astragalus pterocephalus growing in Uzbekistan are a source of triterpene glycosides. The main triterpene glycoside, in terms of content, is a cycloartan glycoside – cyclosiversioside F. To obtain an individual biologically active compound cyclosiversioside F with 95% purity, a proposed method involves extraction with methanol, concentration and dilution with an equal volume of water, then followed by a sequential extraction from the aqueous extract with chloroform, ethyl acetate and butanol. Then a chromatographic separation of the purified amount of extractives on a column with silica gel, isolation of the substance and precipitation from a solvent system must be performed, followed by recrystallization and drying. The optimal conditions for the isolation and separation of the amount of extractive substances have been developed in order to obtain an individual glycoside. Cyclosiversioside F was authenticated by TLC in comparison with an authentic sample. Quantitative analysis of the glycoside was carried out by HPLC. The purity of cyclosiversioside F was confirmed by taking 1H and 13C NMR spectra., Растение Astragalus pterocephalus Bunge, произрастающее в Узбекистане, является источником тритерпеновых гликозидов. Основным гликозидом циклоартанового ряда по содержанию является циклосиверсиозид F. Разработаны оптимальные условия выделения и разделения суммы экстрактивных веществ с целью получения индивидуального гликозида. Для получения индивидуального биологически активного соединения с 95% чистотой предложена методика экстракции метанолом, концентрирование и разбавление равным объемом воды. Затем последовательное извлечение из водного экстракта хлороформом, этилацетатом и бутанолом. Далее – хроматографическое разделение очищенной суммы экстрактивных веществ на колонке с силикагелем, выделение субстанции и осаждение из системы растворителей с последующей перекристаллизацией и сушкой. Установлена подлинность исследуемого соединения с помощью ТСХ в сравнении с аутентичным образцом. Чистоту циклосиверсиозида F подтвердили снятием спектров ЯМР 1Н и 13С. Методом ВЭЖХ проведен количественный анализ гликозида.

Inorganic mesoporous silica gel spheres, which possess sufficient mechanical strength, thermal stability, and mobile phase endurance, are the most important and widely used materials for column packing in high performance liquid chromatography (HPLC). However, amorphous silica gel is generally reported as an inorganic chiral silica gel, and spherical all-inorganic chiral silica gel has not been reportedly used as the chiral stationary phase for HPLC. In this paper, inorganic spherical mesoporous silica gel was used in the method of polymerization-induced colloid aggregation (PICA), with silica sol as the raw material and L-glutamic acid (L-Glu) as the chiral monomer, to obtain mixed spheres of urea-formaldehyde resin and colloidal silica in a chiral environment. After high-temperature calcination (at 550 ℃) to remove the resin, inorganic mesoporous silica gel spheres based on L-Glu were prepared. Elemental analysis revealed that the prepared L-Glu chiral silica gel spheres were calcined completely, indicating that there were no organic constituents. Scanning electron microscopy (SEM) images of the silica gel spheres showed that the surface of the silica gel spheres was not smooth, with a uniform particle size of 3.0-4.5 μm. Transmission electron microscopy (TEM) images showed that the pore size distribution of the synthetic silica gel spheres was uniform due to the accumulation of pores. Nitrogen adsorption tests revealed that the specific surface area of L-Glu chiral silica gel spheres was 117.844 m2/g, the pore volume was 0.411 cm3/g, and the average pore size was 12.312 nm. All the characterizations indicated that the inorganic chiral mesoporous silicon had a regular spherical shape. The silica gel spheres possess frameworks and pore structures, providing a chiral microenvironment that is suitable as a chiral stationary phase for separating racemic compounds by HPLC. Because of the chiral pore structure and frameworks, the enantiomers were retained to different degrees and separation was achieved. The porous structure also increased the contact surface between the racemates and the active sites of the inner wall and improved the separation efficiency. Hydrogen bonding between the chiral stationary phase and the racemates, dipole interactions, and van der Waals forces were also involved in enantiomer resolution. An HPLC column was prepared with L-Glu chiral silica gel as the stationary phase and n-hexane-isopropanol (9∶1, v/v) as the mobile phase. Fifteen racemic compounds were successfully separated on the chiral HPLC column, including seven racemic compounds for baseline separation, at a flow rate of 0.1 mL/min using 254 nm as the detection wavelength at 25 ℃. The separation of 10 benzene position isomers was successfully achieved, and eight of the benzene position isomers reached baseline separation. Experimental results showed that the chiral silica gel spheres possess sufficient mechanical strength and thermal stability, along with good chiral recognition ability and the ability to separate positional isomers. Compared with ordinary silica gel, these chiral silica gel spheres afforded better chiral separation and better separation of benzene position isomers, without further modification. The preparation of this chiral stationary phase also has the advantages of being cheap, convenient, and feasible.

The application of immobilized sulfuric acid on silica gel (H2SO4-SiO2) as an efficient and easily reusable solid catalyst was explored in the synthesis of novel α-acyloxycarboxamide derivatives via a Passerini reaction of benzoic acid, aldehyde/ketone, and isocyanides. The Passerini adducts were obtained in high to excellent yields within 10 min in aqueous media under catalytic conditions. The key advantages of the process include a short reaction time, high yields, the catalyst’s low cost, and the catalyst’s reusability.

The non-polar compounds that coprecipitate with aflatoxins and interfere aflatoxin analysis using an immunoaffinity column (IAC) were identified and an effective pretreatment method was developed in combination with IAC. The proanthocyanidins fractionated from cinnamon coprecipitated with four major aflatoxins (B

A novel method for the synthesis of diarylylnaphtho bis([1,3]oxazine) dione/thione derivatives is established by employing one-pot three-component reaction of naphthalene-1,8-diol/naphthalene-1,5-d...

Prenyl moieties are commonly encountered in the natural products of terpenoid and mixed biosynthetic origin. The reactivity of unsaturated prenyl motifs is less recognized and shown here to affect the acyclic Rhodiola rosea monoterpene glycoside, kenposide A (8), which oxidizes readily on silica gel when exposed to air. The major degradation product mediated under these conditions was a new aldehyde, 9. Exhibiting a shortened carbon skeleton formed through the breakdown of the terminal isopropenyl group, 9 is prone to acetalization in protic solvents. Further investigation of minor degradation products of both 8 and 8-prenylapigenin (8-PA, 12), a flavonoid with an ortho-prenyl substituent, revealed that the aldehyde formation was likely realized through epoxidation and subsequent cleavage at the prenyl olefinic bond. Employment of 1H NMR full spin analysis (HiFSA) achieved the assignment of all chemical shifts and coupling constants of the investigated terpenoids and facilitated the structural validation of the degradation product, 9. This study indicates that prenylated compounds are generally susceptible to oxidative degradation, particularly in the presence of catalytic mediators, but also under physiological conditions. Such oxidative artifact/metabolite formation leads to a series of compounds with prenyl-derived (cyclic) partial structures that are analogous to species formed during Phase I metabolism in vivo. Phytochemical and pharmacological studies should take precautions or at least consider the impact of (unavoidable) exposure of prenyl-containing compounds to catalytic and/or oxidative conditions.

An operationally simple, reliable synthesis of ethynylated acenes suitable for an upper-division undergraduate organic chemistry laboratory course has been developed. This experiment requires students to synthesize two acene derivatives and can be completed in 6–8 laboratory sessions (3 h each); a shorter experiment could be realized in the synthesis of only one product. Synthesis is carried out by first treating a terminal alkyne with n-butyllithium in an oven-dried flask under nitrogen at 0 °C. An acene quinone is added, which produces a doubly ethynylated diol. Dehydration with SnCl2/HCl yields a bis(ethynylated) acene, which is purified via a short pad or column of silica gel. The intense colors of the products allow for great ease in determining reaction completion and following the products in chromatography. UV–vis and fluorescence spectroscopy may be used to better understand the effect of molecular structure on electronic properties.

The key to the online thermal capture of dioxins is the appropriate choice of adsorbent for efficient capture at low temperatures and rapid desorption at high temperatures. Efficient adsorbents can allow for capture and separation during the online monitoring of dioxins or during offline dioxin tests. In this study, 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) and pentachlorodibenzofuran (1,2,3,8,9-PCDF) were used as model compounds for dioxin monomers, and an electron capture detector (ECD) was used to detect the dioxin signals. The retention volumes of 1,2,3,4-TCDD and 1,2,3,8,9-PCDF on 11 types of adsorbents were determined using a packed-column gas chromatography system. Then, the corresponding van der Hoff equation was established, and these adsorbents were evaluated for the thermal trapping of dioxin. The linear coefficients of determination (R2) of these adsorbents were greater than 0.96, which indicated a strong correlation between the adsorption capacity and 1/T (T: temperature). The gas-solid partition coefficients (KSA) of the adsorbent at 120, 150 and 180 ℃ were predicted according to the van der Hoff equation, which was obtained in an earlier study. Among the 11 adsorbents, florite had the largest adsorption capacity at 120, 150, and 180 ℃, especially at 120 ℃; the KSA values for 1,2,3,4-TCDD and 1,2,3,8,9-PCDF on florite were as high as 1.82×108 m3/g and 1.46×1013 m3/g, respectively. Carbon-based adsorbents of the Chinese stilbene polymer porous microspheres GDX series, GDX-101, GDX-102, GDX-103, GDX-105, and GDX-203, can facilitate thermal desorption below 270 ℃, which is the maximum tolerance temperature for series 1 and 2, thus providing evidence for the feasibility of using these adsorbents for the thermal adsorption/desorption of dioxins. When the detection temperature is less than 310 ℃, 1,2,3,4-TCDD is thermally desorbed from mordenite, but 1,2,3,8,9-PCDF is not; this indicates the selective adsorption of dioxin monomers on zeolite. However, diatomite and montmorillonite have poor adsorption capacity for dioxins in the gas phase, thus being unsuitable for the thermal trapping of dioxins. Florite, silica gel, alumina, GDX-102, GDX-103, and GDX-203, which have strong adsorption capacities, were selected as possible absorbents for the next evaluation. Comparison of the lnKSA values of dioxin monomers on the same adsorbent at 120 ℃ and 270 ℃ revealed that the retention volume of florite was the largest at both temperatures. When the thermal trapping performance of dioxin at low temperatures is considered, florite is thought to be the best among the 11 adsorbents for capturing dioxins. However, when the desorption performance at high temperatures is considered, GDX-102 is the best adsorbent for the thermal desorption of dioxins, and its lnKSA,270 ℃ is the smallest among those for the aforementioned six adsorbents. The lnKSA,120 ℃ and lnKSA,270 ℃ values of silica gel, GDX-103, and GDX-203 are similar to those of GDX-102, and hence, they can also be used as rapid thermal adsorption/desorption materials. In this study, the thermal adsorption/desorption properties of 1,2,3,4-TCDD and 1,2,3,7,8-PCDF on 11 adsorbents were systematically evaluated to obtain a new solution for the sampling and preparation of dioxins and to provide technical support for the thermal capture of dioxins. It should be noted that these results were obtained under ideal conditions of nitrogen, without considering the influence of the complex conditions of flue gas (such as moisture and CO2) on the thermal capture. To achieve the thermal capture of dioxins in incineration flue gas, it is necessary to carry out the relevant evaluation and test research in a flue gas atmosphere.

Aldehydes and ketones, available by numerous methods and from plentiful starting materials, are vital classes of chemicals which serve as precursors and intermediates for the preparation of such di...

An HPLC method that separates four Non-Steroidal Anti-Inflammatory Drugs (Ketoprofen, Naproxen, Ibuprofen, and Flurbiprofen) and three of the four pairs of enantiomers in one run is reported. The NSAID samples were prepared with 1 mg/mL of Ketoprofen, Naproxen, Ibuprofen and Flurbiprofen, and 0.5 mg/mL thiourea as a t0 marker in a sample solvent consisting of 1: 1 acetonitrile and 0.2% formic acid. The separation of the enantiomers of the NSAIDs was investigated using a chiral column in two different lengths (5-cm, 10-cm) packed with Amylose tris(3,5-dimethylphenylcarbamate) coated on silica gel and using a tandem column that consists of a biphenyl column connected by a zero dead volume connector to a 5-cm chiral column packed with amylose tris(3,5-dimethylphenylcarbamate) coated on silica gel. Both isocratic and step-gradient methods were investigated, and the results of the different methods were compared to determine the benefits and drawbacks of each approach, with an emphasis on the resolution and analysis time.

Two new sesquiterpene aryl esters, armimelleolides A and B (1 and 2), and four known ones, were isolated from the EtOAc extract of Armillaria gallica 012 m by column chromatography on silica gel, r...