现代分析仪器在高中化学教学中的应用*——以“防晒霜的防晒效果实验探究”为例

从高中化学原子、分子等抽象性的知识教学出发,以防晒霜的防晒效果实验探究为例,探讨了现代分析仪器在高中化学教学中的应用。通过利用现代分析仪器紫外可见分光光度计,结合紫外线变色球实验探究防晒霜的防晒效果,分析并认识防晒霜中化学防晒的机理。结果表明,防晒霜的厚度越大、SPF越高,防晒霜的防晒效果越好,并且防晒霜的防晒效果可以持续一段时间,但是不同类型的防晒产品存在一定差异。在化学教学中渗透现代分析仪器的应用,为学生进一步了解化学学科在改变学习方式、拓宽学科知识领域、推动自身全面与可持续发展方面打下坚实的基础。     

A gadolinium-based magnetic ionic liquid for supramolecular dispersive liquid–liquid microextraction followed by HPLC/UV for the determination of favipiravir in human plasma

Favipiravir is a potential antiviral medication that has been recently licensed for Covid-19 treatment. In this work, a gadolinium-based magnetic ionic liquid was prepared and used as an extractant in dispersive liquid–liquid microextraction (DLLME) of favipiravir in human plasma. The high enriching ability of DLLME allowed the determination of favipiravir in real samples using HPLC/UV with sufficient sensitivity. The effects of several variables on extraction efficiency were investigated, including type of extractant, amount of extractant, type of disperser and disperser volume. The maximum enrichment was attained using 50 mg of the Gd-magnetic ionic liquid (MIL) and 150 μl of tetrahydrofuran. The Gd-based MIL could form a supramolecular assembly in the presence of tetrahydrofuran, which enhanced the extraction efficiency of favipiravir. The developed method was validated according to US Food and Drug Administration bioanalytical method validation guidelines. The coefficient of determination was 0.9999, for a linear concentration range of 25 to 1.0 × 10⁵ ng/ml. The percentage recovery (accuracy) varied from 99.83 to 104.2%, with RSD values (precision) ranging from 4.07 to 11.84%. The total extraction time was about 12 min and the HPLC analysis time was 5 min. The method was simple, selective and sensitive for the determination of favipiravir in real human plasma.     

Processing of lignocellulosic polymer wastes using microwave irradiation

Lignin and mixed lignocellulosic natural polymer wastes have been accumulated in landfills over the past hundred years. These wastes should be processed to produce added- value chemicals and materials. This mini-review presents a brief literature survey related to state-of-the-art methods developed recently by the world research community to solve the problem of rational conversion of lignocellulosic polymer wastes, including production of hydrogen, synthesis gas, phenols, and monomers. The focus is made on microwave and plasma technologies used for lignocellulosic wastes processing.     

Tandem Use of Optical Sensing and Machine Learning for the Determination of Absolute Configuration,Enantiomeric and Diastereomeric Ratios,and Concentration of Chiral Samples

We have developed an optical method for accurate concentration, er, and dr analysis of amino alcohols based on a simple mix‐and‐measure workflow that is fully adaptable to multiwell plate technology and microscale analysis. The conversion of the four aminoindanol stereoisomers with salicylaldehyde to the corresponding Schiff base allows analysis of the dr based on a change in the UV maximum at 420 nm that is very different for the homo‐ and heterochiral diastereomers and of the concentration of the sample using a hypsochromic shift of another absorption band around 340 nm that is independent of the analyte stereochemistry. Subsequent in situ formation of Cu^II assemblies in the absence and presence of base enables quantification of the er values for each diastereomeric pair by CD analysis. Applying a linear programming method and a parameter sweep algorithm, we determined the concentration and relative amounts of each of the four stereoisomers in 20 samples of vastly different stereoisomeric compositions with an averaged absolute percent error of 1.7 %.     

Quantitative determination of potential genotoxic impurity 3-aminopyridine in linagliptin active pharmaceutical ingredient using HILIC–UV

This study aimed to develop an analytical method to determine the quantity of the impurity 3-aminopyridine (3AP). 3-Aminopyridine is a reactive reagent in the synthesis of linagliptin. The method was sensitive at level of 30.0 ppm of 3AP relative to linagliptin. The analysis was carried out using hydrophilic interaction liquid chromatography. The analytical column was Tracer Extrasil Silica (150 × 4.0 mm, 3 μm). A mobile phase of water–acetonitrile (10:90, v/v) containing 10.0 mM ammonium acetate was prepared and adjusted to pH 6.0. A UV detector was used to detect the amount of 3AP at a wavelength of 298 nm. Validation of the method was performed as per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use in terms of detection limit, quantitation limit, linearity, accuracy, precision, specificity and robustness. The calibration curve was linear (r² = 0.999) for 3AP concentration in the range of 30.0–450.0 ppm. This method showed a good sensitivity with a detection limit and a quantitation limit of 7.5 and 25.0 ppm, respectively.     

Study of water uptake in poly(ether ether ketone) irradiated by MeV O+ and Au+ ions

Poly(ether ether ketone) (PEEK) was irradiated with 4?MeV O⁺ and 5 and 10?MeV Au⁺ ions to the fluences from 10¹² to 10^14?cm^?2 and then treated in 5 M/l water solution of LiCl for one month at room temperature. After drying and removal of LiCl surface contamination, the depth distribution of LiCl embeded in PEEK was measured by the neutron depth profilig method (NDP) sensitive to ⁶Li isotope. Embeded LiCl is believed to map distribution of water diffusing into PEEK interior. The results show that the PEEK irradiated to the fluences above 1.10¹³cm^?2 is prone to water penetration to the depths of few microns. On the pristine PEEK and that irradiated to lower ion fluences only a surface Li contamination is observed.     

Insight into copper-mordenite–silica mixtures (CuMOR–SiO2)

A series of ternary CuMOR–SiO₂ mixed materials were prepared by two synthesis approaches (CuMOR1–y–SiO₂ and CuMOR2–y–SiO₂). Extensive characterization was done for both series and some selected materials were tested in CO catalytic oxidation and NO reduction. The presence of CuMOR and SiO₂ segregated phases was observed in both series by XRD, suggesting that silica formation was not inhibited by the mordenite (MOR) presence. UV–Vis results exhibited that Cu ion exchange was successfully done for CuMOR1–y–SiO₂ series. In the CuMOR2–y–SiO₂ series, the amount of copper was below the sensitivity limit of EDS analysis. CuMOR1–50%–SiO₂ catalyst resulted with higher specific surface area and catalytic activity. A possible relation between reduction temperature, the increase in Cu plasmon excitation, and catalytic activity was observed.     

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.     

Rational Molecular Design towards Vis/NIR Absorption and Fluorescence by using Pyrrolopyrrole aza‐BODIPY and its Highly Conjugated Structures for Organic Photovoltaics

Pyrrolopyrrole aza‐BODIPY (PPAB) developed in our recent study from diketopyrrolopyrrole by titanium tetrachloride‐mediated Schiff‐base formation reaction with heteroaromatic amines is a highly potential chromophore due to its intense absorption and fluorescence in the visible region and high fluorescence quantum yield, which is greater than 0.8. To control the absorption and fluorescence of PPAB, particularly in the near‐infrared (NIR) region, further molecular design was performed using DFT calculations. This results in the postulation that the HOMO–LUMO gap of PPAB is perturbed by the heteroaromatic moieties and the aryl‐substituents. Based on this molecular design, a series of new PPAB molecules was synthesized, in which the largest redshifts of the absorption and fluorescence maxima up to 803 and 850 nm, respectively, were achieved for a PPAB consisting of benzothiazole rings and terthienyl substituents. In contrast to the sharp absorption of PPAB, a PPAB dimer, which was prepared by a cross‐coupling reaction of PPAB monomers, exhibited panchromatic absorption across the UV/Vis/NIR regions. With this series of PPAB chromophores in hand, a potential application of PPAB as an optoelectronic material was investigated. After identifying a suitable PPAB molecule for application in organic photovoltaic cells based on evaluation using time‐resolved microwave conductivity measurements, a maximized power conversion efficiency of 1.27 % was achieved.     

Improving the gas barrier,mechanical and thermal properties of poly(vinyl alcohol) with molybdenum disulfide nanosheets

New multifunctional materials with both high structural and gas barrier performances are important for a range of applications. Herein we present a one‐step mechanochemical process to prepare molybdenum disulfide (MoS₂) nanosheets with hydroxy functional groups that can simultaneously improve mechanical strength, thermal conductivity, and gas permittivity of a polymer composite. By homogeneously incorporating these functionalized MoS₂ nanosheets at low loading of less than 1 vol %, a poly(vinyl alcohol) (PVA) polymer exhibits elongation at break of 154%, toughness of 82 MJ/m³, and in‐plane thermal conductivity of 2.31 W/m K. Furthermore, this composite exhibits significant gas barrier performance, reducing the permeability of helium by 95%. Under fire condition, the MoS₂ nanosheets form thermally stable char, thus enhancing the material's resistance to fire. Hydrogen bonding has been identified as the main interaction mechanism between the nanofillers and the polymer matrix. The present results suggest that the PVA composite reinforced with 2D layered nanomaterial offers great potentials in packaging and fire retardant applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 406–414