Copper-immobilized ionic liquid as an alternative to organic solvents in the one-pot synthesis of bioactive dihydropyrano[2,3-c]pyrazole derivatives

In this study, a novel Cu-immobilized ionic liquid (IL)was designed, characterized, and employed as both promoter and solvent in the synthesis of some dihydropyrano[2,3-c]pyrazoles. The synthesized ionic liquid was characterized by ¹H NMR, ¹³C NMR, FTIR, ICP and EDX analysis and showed high catalytic activity to proceed the synthesis of bioactive dihydropyrano[2,3-c]pyrazole derivatives. This method has the advantage of using the IL as a green medium for the synthesize of the products in high to excellent yields within short reaction times.     

Measurement of Residual Dipolar Couplings of Organic Molecules in Multiple Solvent Systems Using a Liquid-Crystalline-Based Medium

Residual dipolar coupling (RDC), a robust anisotropic NMR parameter for structural elucidation of organic molecules, is only accessible in an anisotropic environment. Herein, we introduce a novel alignment medium based on the molecular self-assembly of oligopeptide amphiphile (OPA). This medium is compatible with different intermediate and polar solvent systems, such as CD₃OD, [D₆]DMSO, and D₂O. The preparation of the OPA-based medium is simple and rapid, while only very weak background signals were observed from OPAs. Furthermore, we show that the purity of OPA has only a minor influence on the quality of the RDC data. These advantages allow RDC measurements of organic molecules with different polarities and solubilities with high efficiency and accuracy.     

Synthesis of Honeycomb-Structured Beryllium Oxide via Graphene Liquid Cells

Using high-resolution transmission electron microscopy and electron energy-loss spectroscopy, we show that beryllium oxide crystallizes in the planar hexagonal structure in a graphene liquid cell by a wet-chemistry approach. These liquid cells can feature van-der-Waals pressures up to 1 GPa, producing a miniaturized high-pressure container for the crystallization in solution. The thickness of as-received crystals is beyond the thermodynamic ultra-thin limit above which the wurtzite phase is energetically more favorable according to the theoretical prediction. The crystallization of the planar phase is ascribed to the near-free-standing condition afforded by the graphene surface. Our calculations show that the energy barrier of the phase transition is responsible for the observed thickness beyond the previously predicted limit. These findings open a new door for exploring aqueous-solution approaches of more metal-oxide semiconductors with exotic phase structures and properties in graphene-encapsulated confined cells.     

Amphiphilic poly(ionic liquid)/Wells–Dawson-type phosphovanadomolybdate ionic composites as efficient and recyclable catalysts for the direct hydroxylation of benzene with H2O2

Three novel amphiphilic poly(ionic liquid) (PIL)/Wells–Dawson-type phosphovanadomolybdate (V-POM) ionic composites with tunable oxidative catalytic activity and unique nanostructure were synthesized using carboxylic acid-functionalized PIL and H₇[P₂Mo₁₇VO₆₂], H₈[P₂Mo₁₆V₂O₆₂] and H₉[P₂Mo₁₅V₃O₆₂] as synthetic units via self-assembly in water. The results of characterization indicated that V-POM anions were finely dispersed in the PIL cation framework, and their structures were well preserved. The three composites are amorphous V-POM salts of PIL cation with a considerable thermal stability, and an open three-dimensional network structure with hierarchical porosity. The as-synthesized composites were found to be efficient heterogeneous catalysts for the direct hydroxylation of benzene to phenol with H₂O₂ in the liquid phase. Under optimum conditions, a phenol yield of 37.3% was achieved with selectivity of 100%. The high catalytic performance could be attributed to the synergistic catalytic effect between V-POM anion and carboxylic acid-functionalized PIL cation framework, and good benzene adsorption and phenol desorption ability of amphiphilic micropores in the structure of the composites. Additionally, these composites exhibited high stability under the reaction conditions and could be easily recovered and reused at least six times without noticeably loss of activity.     

Chemical profiling of bioactive constituents in hop cones and pellets extracts by online comprehensive two‐dimensional liquid chromatography with tandem mass spectrometry and direct infusion Fourier transform ion cyclotron resonance mass spectrometry

Humulus lupulus L. (hop) is highly interesting from a nutraceutical perspective. The hop phytocomplex contains a wide range of bioactive metabolites, and its characterization is challenging. To tackle such a task, for the first time we applied and compared a combined approach consisting of online comprehensive two‐dimensional liquid chromatography with tandem mass spectrometry and direct infusion Fourier transform ion cyclotron mass spectrometry. A reversed phase × reversed phase approach with a shifted gradient in the second dimension ensured selectivity and two‐dimensional space coverage. Hyphenation with an ion trap time‐of‐flight analyzer led to the identification of 83 compounds in 70 min, comprising a novel quercetin derivative and six unknown bitter acids. On the other hand, the direct infusion method was able to identify 40 analytes (except isomers) with high mass accuracy (≤ 0.1 ppm) in less than 1 min analysis time. The developed approach can be used in a complementary way, combining the separation capability and high informative spectra of two‐dimensional liquid chromatography tandem mass spectrometry with the ultra‐high mass accuracy of direct infusion, for potential compound discovery or the accurate profiling of bioactive compounds in different hop cultivars as well as for monitoring processing and storage of hop‐based products.     

Rapid analysis of ultraviolet filters using dispersive liquid–liquid microextraction coupled to headspace gas chromatography and mass spectrometry

An ionic‐liquid‐based in situ dispersive liquid–liquid microextraction method coupled to headspace gas chromatography and mass spectrometry was developed for the rapid analysis of ultraviolet filters. The chemical structures of five ionic liquids were specifically designed to incorporate various functional groups for the favorable extraction of the target analytes. Extraction parameters including ionic liquid mass, molar ratio of ionic liquid to metathesis reagent, vortex time, ionic strength, pH, and total sample volume were studied and optimized. The effect of the headspace temperature and volume during the headspace sampling step was also evaluated to increase the sensitivity of the method. The optimized procedure is fast as it only required ∼7–10 min per extraction and allowed for multiple extractions to be performed simultaneously. In addition, the method exhibited high precision, good linearity, and low limits of detection for six ultraviolet filters in aqueous samples. The developed method was applied to both pool and lake water samples attaining acceptable relative recovery values.     

In situ liquid SIMS analysis of uranium oxide

Trace analysis of nuclear materials in solid particles collected in the environment or particles in liquid slurry generated in nuclear material manufacturing processes can pinpoint elemental, organic, and isotopic signatures of nuclear fuel cycle activities and processes. Such information can support nuclear safeguards programs by increasing our ability to detect undeclared nuclear materials, routine activities for safeguarding at declared facilities, and illicit activities. However, trace radioactive material analysis in liquids and slurries is challenging using bulk approaches. For example, one drawback of sensitive analysis such as inductively coupled plasma mass spectrometry (ICP-MS) is that sample is consumed or destroyed as a result of the technical approach. We developed a vacuum compatible microfluidic interface to enable surface analysis of liquids and solid–liquid interactions using time-of-flight secondary ion mass spectrometry (ToF-SIMS). In this work, we illustrate the initial results from the analysis of liquid uranium oxide standard solutions using in situ liquid SIMS. Because the liquid SIMS analysis is almost nondestructive, the same sample can then be analyzed by other analytical techniques or saved for future reference. Consequently, multimodal analysis is possible. Our results demonstrate that in situ liquid SIMS can be used as a new approach to analyze radioactive materials in liquid and slurry forms of relevance to diverse applications.     

Analysis and fate of the hindered amine light stabilizer Tinuvin 622 in polyester powder coatings using high performance liquid chromatography / time of flight mass spectrometry

Hindered amine light stabilizers are used to protect polymers from heat- and light-induced degradation. In this study the oligomeric stabilizer Tinuvin 622 was analysed in-depth employing high performance liquid chromatography/time of flight mass spectrometry (HPLC/TOF-MS) to differentiate products of different manufacturers in respect of their terminating groups and oligomer length. Additionally, the behaviour of the stabilizer in uncured and cured polyester powder coatings was investigated regarding its interaction with the other coating components and chemical changes during the crosslinking process. The extraction efficiency was determined as a function of oligomer length and coating colour.     

Ion pair assisted micro matrix solid phase dispersion extraction of alkaloids from medical plant

A novel micro matrix solid phase dispersion method was successfully used for the extraction of quaternary alkaloids in Phellodendri chinensis cortex. The elution of target compounds was accomplished with sodium hexanesulfonate as the eluent solvent. A neutral ion pair was formed between ion-pairing reagent and positively charged alkaloids in this process, which was beneficial for selectively extraction of polar alkaloids. Several parameters were optimized and the optimal conditions were listed as follows: silica gel as the sorbent, silica to sample mass ratio of 1:1, the grinding time of 1 min. The exhaustive elution of targets was achieved by 200 µL methanol/water (9:1) containing 150 mM sodium hexane sulfonate at pH 4.5. The method validation covered linearity, recovery, precision of intraday and interday, limits of detection, limits of quantitation, and repeatability. This established method was rapid, simple, environmentally friendly, and highly sensitive.     

Analysis of new psychoactive substances in human urine by ultra‐high performance supercritical fluid and liquid chromatography: Validation and comparison

New psychoactive substances represent serious social and health problem as tens of new compounds are detected in Europe annually. They often show structural proximity or even isomerism, which complicates their analysis. Two methods based on ultra high performance supercritical fluid chromatography and ultra high performance liquid chromatography with mass spectrometric detection were validated and compared. A simple dilute‐filter‐and‐shoot protocol utilizing propan‐2‐ol or methanol for supercritical fluid or liquid chromatography, respectively, was proposed to detect and quantify 15 cathinones and phenethylamines in human urine. Both methods offered fast separation (<3 min) and short total analysis time. Precision was well <15% with a few exceptions in liquid chromatography. Limits of detection in urine ranged from 0.01 to 2.3 ng/mL, except for cathinone (5 ng/mL) in supercritical fluid chromatography. Nevertheless, this technique distinguished all analytes including four pairs of isomers, while liquid chromatography was unable to resolve fluoromethcathinone regioisomers. Concerning matrix effects and recoveries, supercritical fluid chromatography produced more uniform results for different compounds and at different concentration levels. This work demonstrates the performance and reliability of supercritical fluid chromatography and corroborates its applicability as an alternative tool for analysis of new psychoactive substances in biological matrixes.