Determination of Organic Compounds in Aqueous–Organic and Dispersed Media Using Electrochemical Methods of Analysis

Journal of Analytical Chemistry - We considered capabilities of electrochemical analysis for the determination of organic compounds in aqueous-organic and dispersed media. The main factors...     

“Activated Borane” – A Porous Borane Cluster Network as an Effective Adsorbent for Removing Organic Pollutants

The unprecedented co-thermolysis of decaborane(14) (nido-B₁₀H₁₄) and toluene results in a novel porous material (that we have named “activated borane”) containing micropores between 1.0 and 1.5 nm in diameter and a specific surface area of 774 m² g⁻¹ (Ar, 87 K) that is thermally stable up to 1000 °C. Solid state ¹H, ¹¹B and ¹³C MAS NMR, UV-vis and IR spectroscopies suggest an amorphous structure of borane clusters interconnected by toluene moieties in a ratio of about three toluene molecules for every borane cluster. In addition, the structure contains Lewis-acidic tri-coordinated boron sites giving it some unique properties. Activated borane displays high sorption capacity for pollutants such as sulfamethoxazole, tramadol, diclofenac and bisphenol A that exceed the capacity of commercially-available activated carbon. The consistency in properties for each batch made, and the ease of its synthesis, make activated borane a promising porous material worthy of broad attention.     

Sensitive and Selective LC–ESI–MS Analysis of Aesculin in Rat Plasma

A rapid and sensitive liquid chromatography–electrospray ionization mass spectrometry method was developed for the determination of aesculin in rat plasma. The analyses were chromatographed on a Zorbax Extend-C18 analytical column (150 × 2.1 mm I.D., 5 µm) with 30:70 (v/v) methanol–0.1% formic acid as mobile phase. Detection was performed by triple-quadrupole tandem mass spectrometry in multi-reaction-monitoring mode with an electrospray ionization source. The method was validated for accuracy and precision, and linearity in the two matrices was good. The assay was linear in the range 12.5–1,800 ng mL^?1. The lower limit of quantification of aesculin (LLOQ) was 12.5 ng mL^?1. The recovery of aesculin and tinidazole (IS) were well above 85%. The within- and between-batch accuracy was 100–104% and 97–109%, respectively. There were no stability-related problems in the procedure for the analysis of aesculin. The method was successfully used in a preclinical study of the pharmacokinetics of aesculin in rats.     

Study on the Methods Of Adsorbent Enriching－SFE Desorbing and Off－line GC－MS－DS Determination of Trace Organic Pollutants from Coal Smoke

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FeIII–Salen-Based Probes for the Selective and Sensitive Detection of E450 in Foodstuff

Inorganic pyrophosphate (PPi) is considered as a diagnostic marker for various diseases such as cancer and vascular calcification. PPi also plays an important preservative role as an additive E450 in foodstuff. In this work, a selective Fe^III–salen-based probe for PPi is described; this probe disassembles in the presence of the target analyte into its molecular blocks, 1,2-propanediamine and 3-chloro-5-formyl-4-hydroxybenzenesulfonic acid. The latter signaling unit leads to a fluorometric response. Compared with a related prototype, the new complex shows a 2.3-times stronger emission at 500 nm and a 155-times better selectivity of PPi over adenosine triphosphate (ATP). Importantly, the new probe was successfully applied for detecting E450 in foodstuff.     

Sensitive and Selective Detection of Enterococcus faecalis Using a New Turn-on Fluorogenic β-glucosidase Substrate Combined with a Modified Selective Broth

A new, simple-to-synthesize and sensitive turn-on fluorogenic substrate ( CFMU-Glu ) for β-glucosidase activity was developed. This probe was based on a 7-hydroxycoumarin derivative ( CFMU ) that could emit green fluorescence and had the low pK_a value of 5.61 ± 0.01. CFMU-Glu could be used for sensitive monitoring of the almond βGLU and Enterococcus faecalis (E. faecalis) at the optimal pHs of 6.50 and 7.00, respectively. Moreover, a new sensitive and selective fluorogenic broth (PBF-B) for E. faecalis, utilizing CFMU-Glu and polymyxin B, was also developed. Polymyxin B was discovered to can significantly improve the detection selectivity and signal intensity. The proposed 4-four method using PBF-B and a microcentrifuge tube could provide fluorogenic detection limits of 5.01 × 10⁴ and 1.0 × 10⁵ CFU mL⁻¹ by fluorescence microplate reader and naked eye, respectively; it could also provide a turn-on chromogenic detection limit of 1.0 × 10⁶ CFU mL⁻¹ by naked eye. The proposed method could detect 8 CFU mL⁻¹ of E. faecalis in drinking water, Liangcha (herbal tea) and milk samples within 10 h, without pre-enrichment.     

Are Organic Certified Carrots Richer in Health-Promoting Phenolics and Carotenoids than the Conventionally Grown Ones?

The aim of the present study was to determine the concentrations of polyphenols and carotenoids by means of HPLC/UV-Vis in certified organic and non-organic carrots (Daucus carota L.) of two cultivars (Flacoro and Nantejska). The analyzed carrot root samples contained, on average, 4.29 ± 0.83 mg/100g f.w. of carotenoids (mainly β-carotene) and 9.09 ± 2.97 mg/100g f.w. of polyphenols, including 4.44 ± 1.42 mg/100g f.w. of phenolic acids and 4.65 ± 1.96 mg/100g f.w. of flavonoids. Significant effects of the production system on the carotenoids (total) and β-carotene concentration were found, with higher concentrations of these compounds generally identified in conventionally cultivated roots (4.67 ± 0.88 mg/100g f.w.) vs. organically grown ones (4.08 ± 0.74 mg/100g f.w.). There was a noticeable inter-sample (inter-farm) variation in the concentration of polyphenols in carrot roots. Despite a general trend towards higher concentrations of these compounds in the organic carrots (9.33 ± 3.17 mg/100g f.w.) vs. conventional carrots (8.64 ± 2.58 mg/100g f.w.), and in those of Nantejska (9.60 ± 2.87 mg/100g f.w.) vs. Flacoro (8.46 ± 3.02 mg/100g f.w.) cultivar, no consistent, statistically significant impact of the production system and/or cultivar on the level of these bioactive compounds was identified. More efforts should be encouraged to ensure that organic crops reaching the market consistently contain the expected high levels of health-promoting bioactive compounds, which could be brought through their shelf-life and all processing steps, in order to meet consumers’ expectations and provide the expected health benefits.     

Electrocatalytic Oxidation of Organic Pollutants on Boron-Doped Diamond and Ti–Ru Oxide Anodes in Sulfate Medium

Electrochemical oxidation for degradation of industrial dye Methyl Orange in aqueous sulfate solutions with various electrocatalytic materials: boron-doped diamond electrode and electrode based on titanium and ruthenium oxides. The influence exerted by the main working parameters of electrolysis (current density, concentration of Methyl Orange, pH) on the discoloration efficiency and on the chemical oxygen demand (COD) was examined. It was shown that an increase in the current density and a decrease in the pollutant concentration improve the process efficiency. However, this leads to an increase in the specific electric energy consumption per unit mass of COD. It was found that the boron-doped diamond electrode is a more efficient electrocatalytic material, compared with electrode based on titanium and ruthenium oxides. At low concentrations of Methyl Orange (<50 mg L^–1), there exists the possibility in principle of using the electrode based on titanium and ruthenium oxides not only for discoloration, but also for making lower the COD level.     

Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks

The semihydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry. Unfortunately, state-of-the-art heterogeneous catalysts hardly achieve high turnover frequencies (TOFs) simultaneously with almost full conversion, excellent selectivity, and good stability. Here, we used metal–organic frameworks (MOFs) containing Zr metal nodes (“UiO”) with tunable wettability and electron-withdrawing ability as activity accelerators for the semihydrogenation of alkynes catalyzed by sandwiched palladium nanoparticles (Pd NPs). Impressively, the porous hydrophobic UiO support not only leads to an enrichment of phenylacetylene around the Pd NPs but also renders the Pd surfaces more electron-deficient, which leads to a remarkable catalysis performance, including an exceptionally high TOF of 13835 h⁻¹, 100 % phenylacetylene conversion 93.1 % selectivity towards styrene, and no activity decay after successive catalytic cycles. The strategy of using molecularly tailored supports is universal for boosting the selective semihydrogenation of various terminal and internal alkynes.     

ON–OFF Fluorescent Imidazole Derivative for Sensitive and Selective Detection of Copper(II) Ions

Russian Journal of Organic Chemistry - A novel multichromophoric hybrid compound, 2-[1-(4-tert-butylphenyl)-4,5-diphenyl-1H-imidazol-2-yl]-6-(pyren-1-yl)quinoline (TDIPQ) has been synthesized as an...     

A Selective and Sensitive Fluorescence Probe for Se(Ⅳ) Based on Fluorescence Quenching of Gatifloxacin

A novel high selective and sensitive fluorescence probe termed gatifloxacin was discovered based on fluorescence "on-off" phenomenon in the presence of Se(Ⅳ). In the Tris-HCl/acetonitrile(3:7, volume ratio, Tris-HCl 0.05 mol/L, pH=7.3) sys-tem, the fluorescence intensity of gatifloxacin was linearly decreased with the concentration increase of Se(Ⅳ) in a range of 1.0×10^-5-5.0×10^-5 mol/L with a correlation coefficient of 0.9979(R²=0.9958) and in a range of 5.0×10^-5-1.0×10^-4 mol/L with a correlation coefficient of 0.9973(R²=0.9946). The detection limit of Se(Ⅳ) was 1.70×10^-6 mol/L.     

Polyoxometalates-Based Metal–Organic Frameworks Made by Electrodeposition and Carbonization Methods as Cathodes and Anodes for Asymmetric Supercapacitors

Hybrid materials have obtained well-deserved attention for energy storage devices, because they show high capacitances and high energy densities induced by the synergistic effect between complementary components. Polyoxometalate-based metal–organic frameworks (POMOFs) possess the abundant redox-active sites and ordered structures of polyoxometalates (POMs) and metal–organic frameworks (MOFs), respectively. Here, an asymmetric supercapacitor (ASC) NENU-5/PPy/60//FeMo/C was fabricated in which both its electrodes are prepared from POMOF precursors. A typical POMOF material, NENU-5, was first connected with polypyrrole (PPy) through electrodeposition to form the cathode material NENU-5/PPy. Another representative POMOFs material, PMo₁₂@MIL-100, was carbonized to obtain the anode material FeMo/C. Cathode NENU-5/PPy exhibited an extraordinary capacitance of 508.62 F g⁻¹ (areal capacitance: 2034.51 mF cm⁻²). In addition, anode FeMo/C shows excellent cyclic stability attributed to its unique structure. Finally, benefiting from the outstanding capacitances and structural merits of the anode and cathode, assembled asymmetric supercapacitor NENU-5/PPy/60//FeMo/C achieves an energy density of 1.12 mWh cm⁻³ at a power density output of 27.78 mW cm⁻³, as well as a notable life of 10 000 cycles with an capacity retention of 80.62 %. Thus, the unique ASC is strongly competitive in high capacitance, long cycle life, and high energy-required energy storage devices.     

Evaluation of Liquid–Liquid Extraction Methods for Determining the Levels of Lipids and Organochlorine Pollutants in Human Milk

Organic chlorine pesticides and polychlorinated biphenyls are organic pollutants that are stored in the adipose tissues of humans. The concentrations of those pollutants in human milk have previously been utilized as a biomarker for monitoring the body burden of lipophilic pollutants in humans. Liquid–liquid extraction methods have been applied to lipids, chlorinated pesticides, and polychlorinated biphenyls from breast milk. In this study, the effectiveness of four extraction methods, which have been widely used to isolate fats and organic pollutants from milk, were compared. The organic solvents included hexane, hexane/acetone (2:1, v/v), ethanol/ethyl ether/hexane (2:3:4, v/v), and methanol/chloroform (1:1, v/v). These results demonstrated that hexane yields the lowest extraction recoveries for lipids (approximately 21.3%) and analytes (approximately 50%). The other three organic solvents demonstrated better performance in extracting the target compounds, with the ethanol/ethyl ether/hexane system showing the optimum efficiency. The optimized system was employed to determine the analytes in human milk.     

Methods of Encapsulation of Biomacromolecules and Living Cells. Prospects of Using Metal–Organic Frameworks

Russian Journal of Organic Chemistry - The review discusses different methods of encapsulation and biomineralization of macromolecules and living cells. Main advantages and disadvantages of most...     

Photoredox Catalysis of Aromatic β-Ketoesters for in Situ Production of Transient and Persistent Radicals for Organic Transformation

Radical formation is the initial step for conventional radical chemistry. Reported herein is a unified strategy to generate radicals in situ from aromatic β-ketoesters by using a photocatalyst. Under visible-light irradiation, a small amount of photocatalyst fac-Ir(ppy)₃ generates a transient α-carbonyl radical and persistent ketyl radical in situ. In contrast to the well-established approaches, neither stoichiometric external oxidant nor reductant is required for this reaction. The synthetic utility is demonstrated by pinacol coupling of ketyl radicals and benzannulation of α-carbonyl radicals with alkynes to give a series of highly substituted 1-naphthols in good to excellent yields. The readily available photocatalyst, mild reaction conditions, broad substrate scope, and high functional-group tolerance make this reaction a useful synthetic tool.