Ionic silsesquioxane film immobilized on silica applied in the development of carbon paste electrode for determination of methyl parathion

A mesoporous silica-based hybrid material composed of silica xerogel modified with an ionic silsesquioxane, which contains the 1,4-diazoniabicyclo[2.2.2]octane chloride group, was obtained. The silsesquioxane film is highly dispersed on the surface. This hybrid material was utilized to develop a carbon paste electrode (CPE) for determination of methyl parathion. Transmission FTIR, elemental analysis and N₂ adsorption–desorption isotherms were used for characterization of the material. The electrochemical behavior of methyl parathion was evaluated by cyclic voltammetry and differential pulse voltammetry. It was observed a linear response to methyl parathion in the concentration range from 1.25 × 10^?7 to 2.56 × 10^?6 mol L^?1 by employing the carbon paste electrode, in Britton–Robinson buffer solution (pH 6). The achieved detection limit (3 SD of the blank divided by the slope of calibration curve) was 0.013 µmol L^?1 and sensitivity was 6.3 µA µmol L^?1. This result shows the potentiality of this electrode for application as electrochemical sensor for methyl parathion.     

Pomegranate rind-derived activated carbon as electrode material for high-performance supercapacitors

In this paper, activated carbon materials were synthesized from pomegranate rind through carbonization and alkaline activation processes. The effects of pyrolytic temperature on the textual properties and electrochemical performance were investigated. The surface area of the activated carbon can reach at least 2200 m² g^?1 at different pyrolytic temperatures. It was found that, at the range of 600–900 °C, decreasing the carbonization temperature leads to the increase of t-plot micropore area, t-plot micropore volume, and capacitance. Further decreasing the carbonization temperature to 500 °C also leads to the increase of t-plot micropore area and t-plot micropore volume, but the capacitance is slightly poorer. The activated carbon carbonized at 600 °C and activated at 800 °C possesses very high specific area (2931 m² g^?1) and exhibits very high capacitance (～268 F g^?1 at 0.1 A g^?1 and ～242 F g^?1 at 1 A g^?1). There is no capacitance fading after 2000th cycle.     

Aminophylline: thermal characterization and its inhibitory properties for the carbon steel corrosion in acidic environment

Aminophylline (AMF) was studied as corrosion inhibitor for carbon steel in 1.0 mol L^?1 HCl solution using electrochemical measurements associated with UV–Vis spectrophotometry and optical microscopy. Simultaneous thermogravimetry/derivative thermogravimetry and differential scanning calorimetry analysis was performed in order to determine the temperature range in which AMF is an effective inhibitor, without the decomposition risk that could change the inhibition mechanism. Thermal behaviour restricts AMF application as corrosion inhibitor for carbon steel in 1.0 mol L^?1 HCl solution at temperatures ≤45 °C where there are no significant modifications of the adsorption mechanism. According to the results of electrochemical measurements, in association with UV–Vis spectrophotometry and optical microscopy techniques, AMF is a mixed-type inhibitor for carbon steel corrosion in 1.0 mol L^?1 HCl solution, simultaneously suppressing the anodic and cathodic processes and acting via spontaneous physisorption on the metal surfaces.     

Evaluation of natural gamma radiation and absorbed gamma dose in soil and rocks of Perambalur district (Tamil Nadu,India)

The activity concentrations and absorbed gamma dose of primordial radionuclides ²³⁸U, ²³²Th and ⁴⁰K were determined employing γ-ray spectrometry in 31 soil samples from the land area earmarked for house construction in Perambalur district and 14 rock samples from quarries that supply stones for the entire district. The soil samples registered relatively a higher mean value of 13.2 Bq kg^?1 for ²³⁸U, 66 Bq kg^?1 for ²³²Th and 340.3 Bq kg^?1 for ⁴⁰K as compared to mean values for rock samples (²³⁸U—8.0 Bq kg^?1; ²³²Th—65.1 Bq kg^?1; ⁴⁰K—199.1 Bq kg^?1). The mean absorbed gamma dose rate for soil (61.4 nGy h^?1) marginally exceeded the prescribed limit of 55 nGy h^?1 while, rocks registered the mean absorbed gamma dose rate of 10.4 nGy h^?1. The mean radium equivalent activity was distinctly higher in soil (130.6 Bq kg^?1) than in rock (20.0 Bq kg^?1). However, these values were lower than the limit (370 Bq kg^?1) set by OECD for building materials. It is evident from the data that the soil and rocks do not pose any radiological risk for house constructions in Perambalur district.     

A sustainable synthesis of biomass carbon sheets as excellent performance sodium ion batteries anode

Biomass-derived carbon (BMC) materials have attracted much attention due to their high performance and properties of abundant source. Herein, biomass carbon sheets (BMCS) from wheat straws had been successfully synthesized via a facile high temperature carbonization and expansion processes. The morphology of BMCS keeps the natural honeycomb-like shape of the cross section and the hollow tubular array structure of the vertical section with rich pores, which provides low-resistant ion channels to support fast diffusion. The (002) crystal plane reveals that the intercalation distance of carbon sheets is 0.383 nm larger than that graphite (0.335 nm), which benefits the larger sodium ion de/intercalation. By comparing different carbonization temperatures, wheat straws carbonized at 1200 °C (BMCS-1200) with well graphite microcrystallites show more excellent sodium ion storage performance than that of 900 °C (BMC-900). BMCS-1200 shows a stable reversible capacity of 221 mAh g^?1 after 200 cycles at 0.05 A g^?1, while BMC-900 is 162 mAh g^?1 after 100 cycles. And it also exhibits better rate capability (220, 109 mAh g^?1) than that of BMC-900 (125, 77 mAh g^?1) at 0.2 and 1 A g^?1, respectively. Finally, it delivers 89 mAh g^?1 stable capacity after 1400 cycles at 1 A g^?1 to prove its excellent long-term cycling stability.

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Graphical abstract High temperature carbon sheets with well graphite microcrystallites synthesized from wheat straw forexcellent sodium ion storage performance

     

Fast co-pyrolysis of coal and biomass in a fluidized-bed reactor

Co-pyrolysis is one of the most promising options for the utilization of coal and biomass. Coal/biomass blends were prepared using Yilan subbituminous (YL) and corncob and the mass ratios of coal in mixtures varied between 0 and 100 %. Co-pyrolysis characteristics were investigated in a thermogravimetric analyzer from 303 to 973 K under the nitrogen flow of 100 mL min^?1. The co-pyrolysis residues were less than the sum simply added of the solid yields of individuals. With heating rate increased from 10 to 40 K min^?1, the residues decreased more severely compared to the expected under various blending ratios. For fast pyrolysis in fluidized-bed reactor, gas volumes and char yields of co-pyrolysis showed a significant linearity. But pyrolysis-oil yields were higher than the expected from the additive model when the YL blending ratios were less than 60 %. The co-pyrolysis evolved more H₂, CH₄, C₂ + C₃, and less CO than an additive pyrolysis process of individual fuel. The GC/MS results indicated that co-pyrolysis-oil contained more alcohols, ketones, aldehydes, or acids than that of individual fuel. All of that suggested the H/OH in volatiles produced from rapid pyrolysis of biomass transferred to the radicals of coal pyrolysis. The possible reaction mechanism also was provided in the paper.     

Expression,Purification, and Characterization of NADP+-Dependent Malic Enzyme from the Oleaginous Fungus Mortierella Alpina

Malic enzymes are a class of oxidative decarboxylases that catalyze the oxidative decarboxylation of malate to pyruvate and carbon dioxide, with concomitant reduction of NAD(P)⁺ to NAD(P)H. The NADP⁺-dependent malic enzyme in oleaginous fungi plays a key role in fatty acid biosynthesis. In this study, the malic enzyme-encoding complementary DNA (cDNA) (malE1) from the oleaginous fungus Mortierella alpina was cloned and expressed in Escherichia coli BL21 (DE3). The recombinant protein (MaME) was purified using Ni-NTA affinity chromatography. The purified enzyme used NADP⁺ as the cofactor. The K _m values for l-malate and NADP⁺ were 2.19?±?0.01 and 0.38?±?0.02 mM, respectively, while the V _max values were 147?±?2 and 302?±?14 U/mg, respectively, at the optimal condition of pH 7.5 and 33 °C. MaME is active in the presence of Mn²⁺, Mg²⁺, Co²⁺, Ni²⁺, and low concentrations of Zn²⁺ rather than Ca²⁺, Cu²⁺, or high concentrations of Zn²⁺. Oxaloacetic acid and glyoxylate inhibited the MaME activity by competing with malate, and their K _i values were 0.08 and 0.6 mM, respectively.     

Investigation of volatile metabolites during growth of Escherichia coli and Pseudomonas aeruginosa by needle trap-GC-MS

A new method for the growth-dependent headspace analysis of bacterial cultures by needle trap (NT)-gas chromatography-mass spectrometry (GC-MS) was established. NTs were used for the first time as enrichment technique for volatile organic compounds (VOCs) in the headspace of laboratory cultures. Reference strains of Escherichia coli and Pseudomonas aeruginosa were grown in different liquid culture media for 48 h at 36 °C. In the course of growth, bacterial culture headspace was analysed by NT-GC-MS. In parallel, the abiotic release of volatile organic compounds (VOC) from nutrient media was investigated by the same method. By examination of microbial headspace samples in comparison with those of uninoculated media, it could be clearly differentiated between products and compounds which serve as substrates. Specific microbial metabolites were detected and quantified during the stationary growth phase. P. aeruginosa produced dimethyl sulfide (max. 125 μg L^?1??1) and 2-nonanone (max. 200 μg L^?1), whereas E. coli produced carbon disulfide, butanal and indole (max. 149 mg L^?1). Both organisms produced isoprene. Graphical Abstract

MVOCs produced by P. aeruginosa and E. coli at T = 36 °C in autoclaved LB + TRP medium      

Analysis of drug interactions with very low density lipoprotein by high-performance affinity chromatography

High-performance affinity chromatography (HPAC) was utilized to examine the binding of very low density lipoprotein (VLDL) with drugs, using R/S-propranolol as a model. These studies indicated that two mechanisms existed for the binding of R- and S-propranolol with VLDL. The first mechanism involved non-saturable partitioning of these drugs with VLDL, which probably occurred with the lipoprotein’s non-polar core. This partitioning was described by overall affinity constants of 1.2 (±0.3)?×?10⁶ M^?1 for R-propranolol and 2.4 (±0.6)?×?10⁶ M^?1 for S-propranolol at pH 7.4 and 37 °C. The second mechanism occurred through saturable binding by these drugs at fixed sites on VLDL, such as represented by apolipoproteins on the surface of the lipoprotein. The association equilibrium constants for this saturable binding at 37 °C were 7.0 (±2.3)?×?10⁴ M^?1 for R-propranolol and 9.6 (±2.2)?×?10⁴ M^?1 for S-propranolol. Comparable results were obtained at 20 and 27 °C for the propranolol enantiomers. This work provided fundamental information on the processes involved in the binding of R- and S-propranolol to VLDL, while also illustrating how HPAC can be used to evaluate relatively complex interactions between agents such as VLDL and drugs or other solutes.     

Performance and Bacterial Population Composition of an n-Hexane Degrading Biofilter Working Under Fluctuating Conditions

In this work, several conditions of pH and inlet load (IL) were applied to a scale laboratory biofilter treating n-hexane vapors during 143 days. During the first 79 days of operation (period 1, P1), the system was fed with neutral pH mineral medium (MM) and the IL was progressively decreased from 177 to 16 g m^?3 h^?1. A maximum elimination capacity (EC) of 30 g m^?3 h^?1 was obtained at an IL of 176.9?±?9.8 g m^?3 h^?1. During the following 64 days (period 2, P2), acidic conditions were induced by feeding the biofilter with acidic buffer solution and pH 4 MM in order to evaluate the effect of bacterial community changes on EC. Within the acidic period, a maximum EC of 54 g m^?3 h^?1 (IL 132.3?±?13 g m^?3 h^?1) was achieved. Sequence analysis of 16S rDNA genes amplified from the consortium revealed the presence of Sphingobacteria, Actinobacteria, and α-, β- and γ-Proteobacteria. An Actinobacteria of the Mycobacterium genus had presence throughout the whole experiment of biofiltration showing resistance to fluctuating pH and IL conditions. Batch tests confirm the bacterial predominance and a negligible contribution of fungi in the degradation of n-hexane.     

The Development and Validation of a Stability-Indicating UHPLC-DAD Method for Determination of Perindopril l-Arginine in Bulk Substance and Pharmaceutical Dosage Form

A stability-indicating ultra-high-performance liquid chromatography (UHPLC) method with a diode array detector was developed and validated for the determination of cis/trans isomers of perindopril l-arginine in bulk substance and pharmaceutical dosage form. The separation was achieved on a Poroshell 120 Hilic (4.6 × 150 mm, 2.7 µm) column using a mobile phase composed of acetonitrile–0.1 % formic acid (20:80 v/v) at a flow rate of 1 mL min^?1. The injection volume was 5.0 µL and the wavelength of detection was controlled at 230 nm. The selectivity of the UHPLC-DAD method was confirmed by determining perindopril l-arginine in the presence of degradation products formed during acid–base hydrolysis and oxidation as well as degradation in the solid state, at an increased relative air humidity and in dry air. The method’s linearity was investigated in the ranges 0.40–1.40 µg mL^?1 for isomer I and 0.40–2.40 µg mL^?1 for isomer II of perindopril l-arginine. The UHPLC-DAD method met the precision and accuracy criteria for the determination of the isomers of perindopril l-arginine. The limits of detection and quantitation were 0.1503 and 0.4555 µg mL^?1 for isomer I and 0.0356 and 0.1078 µg mL^?1 for isomer II, respectively.     

Titanium dioxide nanoparticle based solid phase extraction of trace Alizarin Violet,followed by its specrophotometric determination

Nanometer-sized titanium dioxide (nano-TiO₂) is shown to be a viable material for the preconcentration of Alizarin Violet (AV, a common dye and biological stain). In the preconcentration step, a 5-ring cyclic ester is formed between the ortho-dihydroxy groups of AV and two hydroxy groups of the titanic acid on the surface of the nano-TiO₂. Under optimized conditions, the adsorption capacity of nano-TiO₂ is?~?20 μg?·?mg^?1, the adsorption efficiency is 98 %. The adsorbed AV can be eluted with 5 mL of 5 mol?·?L^?1 5-sulfosalicylic acid with an elution efficiency of more than 91.8 %. The preconcentration factor is 50 in case of 250 mL samples. Spectrophotometric determination of AV in the eluate gives a linear calibration plot in the range between 18.8 μg?·?L^?1 and 10 mg?·?L^?1 and a detection limit (3 s; for n?=?11) of 18.8 μg?·?L^?1. The method is simple and fast. It was successfully applied to the analysis of AV in spiked natural waters, and recoveries were found to range between 94.2 and 97.3 %.

Nanometer-sized titanium dioxide is a viable material for the preconcentration of Alizarin Violet (AV), before its spectrophotometrical determination. The method is simple and fast. It was successfully applied to the analysis of AV in spiked natural waters, and recoveries were found to range between 94.2 and 97.3 %.     

Carbon composite-based DNA sensor for detection of bacterial meningitis caused by Neisseria meningitidis

Carbon/1-octadecanethiol-carboxylated multiwalled carbon nanotubes (cMWCNT) composite was used to construct a DNA sensor for detection of human bacterial meningitis caused by Neisseria meningitidis. The carbon composite electrode was used to covalently immobilize 5′-amine-labeled 19-mer single-stranded DNA (ssDNA) probe, which was hybridized with 1.35?×?10²–3.44?×?10⁴ pM (0.5–128 ng/5 μl) of single-stranded genomic DNA (ssG-DNA) of N. meningitidis for 10 min at room temperature (RT). The surface topography of the DNA sensor was characterized by using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) while electrochemically characterized by electrochemical impedance. The immobilization of ssDNA probe and hybridization with ssG-DNA were detected electrochemically by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at RT in 30 min with a response time of 1 min. The DNA sensor showed high pathogenic specificity and can distinguish among complement, noncomplement, one base mismatch, and triple base mismatch oligomer targets. The limit of detection (LOD) and sensitivity of the sensor were approximately 68 pM and 38.095 (μA/cm²)/nM of ssG-DNA, respectively, using DPV. The improved sensitivity and LOD of the sensor can be attributed to the higher efficiency of probe immobilization due to high surface area-to-volume ratio and good electrical activity of cMWCNT. Figure

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Transparent poly(thiourethane-urethane)s based on dithiol chain extender

New segmented poly(thiourethane-urethane)s (PTU-Us) (with hard-segment content of 30–60 mass%) were synthesized by a one-step melt polymerization from poly(oxytetramethylene) diol of \( \overline{M}_{n} \)  = 1,000 g mol^?1 or \( \overline{M}_{n} \)  = 2,000 g mol^?1 or poly(hexamethylene carbonate) diol of \( \overline{M}_{n} \)  = 860 g mol^?1 as soft segments, 1,1′-methanediylbis(4-isocyanatocyclohexane) (Desmodur W ^®) and (methylenedi-1,4-phenylene)dimethanethiol as a chain extender. The PTU-Us were examined by FTIR, GPC, XRD, DSC, TG, Shore hardness, and tensile testing. Moreover, refractive index, transparency, adhesive properties, and resistance to bacteria and fungi were determined for selected polymers. The obtained high-molar-mass amorphous polymers showed elastomeric or plastic properties. Their T _gs were in the range from ?70 to 58 °C. The PTU-Us with the polycarbonate soft segments demonstrated a better segmental miscibility (higher T _gs), transparency as well as generally higher tensile strength and hardness than those with the polyether soft segments. All the synthesized PTU-Us showed a relatively good thermal stability. The temperature of 1 % mass loss of all PTU-Us was in the range of 236–255 °C. The introduction of thiourethane linkages to polyurethane chain caused increase of the adhesive strength on copper–polymer junction and refractive index values. From the microbial studies, it was found that the obtained polymers had delayed the growth of Gram-positive bacteria.     

Effects of type of nanosized carbon black on the performance of an all-solid-state potentiometric electrode for nitrate

The potentiometric properties of all-solid-state nitrate-selective electrodes based on plasticized PVC and containing different types of nanosized carbon black were investigated. The use of a carbon black interlayer is shown to significantly improve the potentiometric response. The electrodes display a close-to-Nernstian slope in the range from 10^?1 to 10^?6 M, highly stable potentials and low membrane resistance. However, different analytical features were found depending on the type of carbon black used. The best long-term potential stability was observed for the electrode with Printex XE2-B carbon black that has a relatively high BET surface area (1000 m²?·?g^?1) and an average particle size of 30 nm. Nevertheless, the electrodes with the Vulcan XC-72 (BET surface: 240 m²?·?g^?1; average size: 55 nm) showed the most repeatable and reproducible standard potential. The lowest detection limit for nitrate (2.5·10^?7 M) is observed for an electrode containing Vulcan XC-72.

A nano self-assembled artificial peroxidase: spectroscopic and electrochemical investigations

A nano-micelle with highly efficient peroxide activity was constructed by self-assembly of sodium dodecyl sulfate micellar, histidine and hematin in 50 mM phosphate buffer at 25 °C. UV–Vis spectrometry methods were utilized for characterization of the nanostructured material or artificial peroxidase (AP). The Michaelis–Menten (K _m) and catalytic rate (k _cat) constants of the AP were obtained to be 5.5 μM and 0.06 s^?1, respectively, in 50 mM phosphate buffer solution at pH 8.0. The catalytic efficiency of AP was evaluated to be 0.011 μM^?1 s^?1. The AP was also immobilized on a functional multi-wall carbon nanotubes-gold nanoparticles (AuNPs) nano-complex modified glassy carbon electrode (GCE). The transmission electron microscopy method was utilized for the characterization of the nano-materials. The electron-transfer rate constant (k _s) and the apparent Michaelis–Menten constant K _m ^app of the AP modified GCE were evaluated to be 1.36 s^?1 and 0.19 μM, respectively. For a biosensor without a redox protein, the properties of the AP modified GCE were significant and will further benefit from additional studies and improvement.     

Synthesis of hierarchical free-standing NiMoO<Subscript>4</Subscript>/reduced graphene oxide membrane for high-performance lithium storage

Free-standing and flexible NiMoO₄ nanorods/reduced graphene oxide (rGO) membrane with a 3D hierarchical structure was successfully synthesized by a general approach including vacuum filtration followed by thermal reduction. NiMoO₄ nanorods with about 50–100 nm diameter were embedded homogenously into the 3D rGO sheets and assembled with rGO to form a membrane about 10 μm in thickness. The NiMoO₄/rGO membrane could be directly evaluated as anode materials for lithium-ion batteries (LIBs) without using binder. The 3D layer stacked graphene hierarchical architecture can not only offers a continuous conducting framework for efficient diffusion and transport of ion/electron but also accommodates the large volume expansion of NiMoO₄ nanorod changes during cycling. Moreover, our results show that the NiMoO₄/rGO membrane exhibited excellent electrochemical performance with a high reversible capacity of 945 mAh g^?1 at a current density of 0.25 A g^?1 as anode materials in LIBs.

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Graphical abstract ?

     

Determination of methylisothiocyanate in soil and water by HS-SPME followed by GC–MS–MS with a triple quadrupole

Methylisothiocyanate (MITC) is the main degradation product of metam sodium, a soil disinfectant widely used in agriculture, and is responsible for its disinfectant properties. Because MITC is highly toxic and volatile, metam sodium has to be applied in a manner that tries to reduce atmospheric emissions but still maintains adequate concentration of MITC in soil to ensure its disinfectant effect. Thus, monitoring of MITC concentrations in soil is required, and to this end sensitive, fast, and reliable analytical methods must be developed. In this work, a headspace solid-phase microextraction (HS-SPME) method was developed for MITC determination in water and soil samples using gas chromatography-tandem mass spectrometry (GC–MS–MS) with a triple-quadrupole analyzer. Two MS–MS transitions were acquired to ensure the reliable quantification and confirmation of the analyte. The method had linear behavior in the range tested (0.026–2.6 ng mL^?1 in water, 1–100 ng g^?1 in soil) with r ² over 0.999. Detection limits were 0.017 ng mL^?1 and 0.1 ng g^?1 in water and soil, respectively. Recoveries for five replicates were in the range 76–92 %, and RSD was below 7 % at the two spiking levels tested for each matrix (0.1 and 1 ng mL^?1 for water, 4 and 40 ng g^?1 for soil). The potential of using multiple HS-SPME for analyzing soil samples was also investigated, and its feasibility for quantification of MITC evaluated. The developed HS-SPME method was applied to soil samples from experimental plots treated with metam sodium following good agriculture practices. Figure

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Rapid screening and detection of XOD inhibitors from S. tamariscina by ultrafiltration LC-PDA–ESI-MS combined with HPCCC

Xanthine oxidase (XOD) catalyzes the metabolism of hypoxanthine and xanthine to uric acid, the overproduction of which could cause hyperuricemia, a risk factor for gout. Inhibition of XOD is a major treatment for gout, and biflavonoids have been found to act as XOD-inhibitory compounds. In this study, ultrafiltration liquid chromatography with photodiode-array detection coupled to electrospray-ionization tandem mass spectrometry (UF-LC-PDA–ESI-MS) was used to screen and identify XOD inhibitors from S. tamariscina. High-performance counter-current chromatography (HPCCC) was used to separate and isolate the active constituents of these XOD inhibitors. Furthermore, ultrahigh-performance liquid chromatography (UPLC) and triple-quadrupole mass spectrometry (TQ-MS) was used to determine the XOD-inhibitory activity of the obtained XOD inhibitors, and enzyme kinetics was performed with Lineweaver–Burk (LB) plots using xanthine as the substrate. As a result, two compounds in S. tamariscina were screened as XOD inhibitors: 65.31 mg amentoflavone and 0.76 mg robustaflavone were isolated from approximately 2.5 g?S. tamariscina by use of HPCCC. The purities of the two compounds obtained were over 98 % and 95 %, respectively, as determined by high-performance liquid chromatography (HPLC). Lineweaver–Burk plot analysis indicated that amentoflavone and robustaflavone were non-competitive inhibitors of XOD, and the IC ₅₀ values of amentoflavone and robustaflavone for XOD inhibition were 16.26 μg mL^?1 (30.22 μmol L^?1) and 11.98 μg mL^?1 (22.27 μmol L^?1), respectively. The IC ₅₀ value of allopurinol, used as the standard, was 7.49 μg mL^?1 (46.23 μmol L^?1). The results reveal that the method for systematic screening, identification, and isolation of bioactive components in S. tamariscina and for detecting their inhibitory activity using ultrafiltration LC–ESI-MS, HPCCC, and UPLC–TQ-MS is feasible and efficient, and could be expected to extend to screening and separation of other enzyme inhibitors. Graphical Abstract

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Activated nitrogen-doped carbons from polyvinyl chloride for high-performance electrochemical capacitors

Activated nitrogen-doped carbons (ANCs) were prepared by carbonization/activation approach using aminated polyvinyl chloride (PVC) as precursor. ANCs exhibit larger porosities and higher specific surface areas than those of their nitrogen-free counterparts for the same KOH/carbon ratio. The specific surface area of ANC-1 is up to 1,398 m² g^?1 even at a low KOH/carbon ratio of 1:1. Fourier transform infrared spectroscopy investigation of the nitrogen-enriched resin precursor indicates the efficient dehydrochlorination of PVC by ethylenediamine at a low temperature. The nitrogen content and the population of nitrogen functionalities strongly depend on the KOH/carbon ratios and decrease drastically after KOH activation as seen from the elemental and X-ray photoelectron spectroscopy analysis. The surface concentration of N-6 and N-Q almost disappears and the dominant nitrogen groups become N-5 after KOH activation. The highest specific capacitance of ANCs is up to 345 F g^?1 at a current density of 50 mA g^?1 in 6 M KOH electrolyte. ANCs also exhibit a good capacitive behavior at a high scan rate of 200 mV s^?1 and an excellent cyclability with a capacitance retention ratio as high as ～93 % at a current density of 2,000 mA g^?1 for 5,000 cycles.