阳离子聚丙烯酰胺的聚合方法研究进展

论文评述和探讨了目前阳离子聚丙烯酰胺的几种常见的聚合方法,包括水溶液聚合、反相乳液聚合、分散聚合及光引发聚合,对各聚合方法的优缺点进行了比较,并且对各种方法的产业化进行了分析,提出了光引发聚合法的发展前景,认为有必要深入开展光引发聚合机理及相关技术研究。     

氟掺杂提高纳米二氧化钛光催化活性的研究进展

纳米二氧化钛(TiO2)具有光催化活性高、无毒、化学性质稳定、成本低等优点,是目前最具发展前景的光催化剂。但TiO2的宽禁带和低量子效率限制了它的实际应用。因此,对TiO2进行改性研究,实现TiO2的可见光响应和提高其量子效率成为研究的热点。氟掺杂不仅能够使TiO2具有可见光催化活性,而且可提高其紫外光催化活性。本文综述了氟掺杂TiO2的制备,氟掺杂提高TiO2光催化活性的机理、氟与其他元素共掺杂TiO2的研究进展。     

超声波辅助提纯氢化枞酸的研究

以氢化松香为原料、乙醇胺为有机胺、乙酸乙酯为溶剂,在超声波辅助下进行胺化反应制备氢化枞酸乙醇胺盐,再经萃取、重结晶和酸化得到氢化枞酸,采用正交试验考察了超声功率、搅拌转速、反应温度、反应时间对氢化枞酸纯度的影响,结果表明,影响氢化枞酸纯度因素按显著程度依次为反应温度>反应时间>超声波功率>搅拌转速,确定了最佳的胺化反应条件为:反应温度40℃、反应时间40min、超声波功率400W、搅拌转速400r/min,所得氢化枞酸的纯度为94.5%。采用GC、GC-MS、FT-IR、熔点仪和旋光仪对氢化枞酸产品进行了分析鉴定。     

A DFT study of cage compounds: 3, 5, 8, 10, 11, 12-hexanitro-3, 5, 8, 10, 11, 12-hexaazatetracyclo [5.5.1.12,6.04,9] dodecane and its derivatives as high energetic materials

A new cage compound, 3, 5, 8, 10, 11, 12-hexanitro-3, 5, 8, 10, 11, 12-hexaazatetracyclo [5.5.1.1^2,6.0^4,9] dodecane (HNHATCD, I) as well as its –ONO₂ (II) and –N₃ (III) derivatives were proposed in the present work. Their molecular structures were optimized at the B3LYP/6-31G(d,p) level of density functional theory. Heat of formation, strain energy, detonation performance, and thermal stability were studied. Results show that the –N₃ group greatly increases the heat of formation, but decreases the strain energy and density, and it is much more helpful for enhancing the detonation energy than the –NO₂ and –ONO₂ groups. An analysis of bond dissociation energies (BDEs) of the weakest bonds implies that the BDE of –N₃ derivatives is the smallest but it is still larger than 120 kJ mol^?1, revealing that these designed compounds have a high thermal stability. Considering the detonation performance and thermal stability, I and II may be potential candidates of high energy density materials.     

Simultaneous quantitation of seven alkaloids in processed Fuzi decoction by rapid resolution liquid chromatography coupled with tandem mass spectrometry

A rapid analytical method based on rapid resolution LC coupled with MS/MS was first established to quantify seven alkaloids in processed Fuzi decoction. The chromatographic method was optimized to allow simultaneous analysis of all analytes in 5 min and demonstrated good linearity (r > 0.9995), repeatability (RSD < 4.36%), intra‐ and interday precisions (RSD < 5.07%) with good accuracies (97.76–105.08%) and good recovery (95.0–107.5%) of seven alkaloids, namely higenamine, benzoylhypaconine, benzoylmesaconine, benzoylaconine, aconitine, hypaconitine, and mesaconitine. The LODs for these markers were in the range of 2.30–17.00 pg/mL. Quantitative analysis of the seven alkaloids in Baifupian decoction and Heishunpian decoction showed that the content of the seven marker chemicals varied significantly and concluded that the quality of Fuzi was greatly affected by different processed methods. The developed method could be used as a rapid, sensitive, and reliable approach for assessment of the quality of processed Fuzi and related decoction.     

Separation,interconversion, and insecticidal activity of the cis‐ and trans‐isomers of novel hydrazone derivatives

A series of cis‐ and trans‐isomers of hydrazone derivatives were separated and analyzed through HPLC with diode‐array detection and HPLC‐MS/MS using ESI and ion trap MS. Two single crystals (A‐5‐1 and C‐2‐1) of the trans‐isomers were obtained and determined using X‐ray crystallography data, and the cis‐ to trans‐isomerization under different conditions was discussed. Both of the cis‐ and trans‐isomers of A‐4 and A‐5 exhibited good insecticidal activities against Plutella xylostella.     

Simultaneous determination of 11 related impurities in propofol by gas chromatography/tandem mass spectrometry coupled with pulsed splitless injection technique

A variety of related impurities, including starting materials, process impurities, and degradation products, can be detected in propofol. In this article, a sensitive and selective GC‐MS/MS method using pulsed splitless injection technique for the determination of 11 main related impurities in propofol in one chromatogram is investigated. This method is extensively validated for its linearity, recovery, precision, LOD, and LOQ, and is able to detect trace‐level related impurities (LOD = 0.2–5.6 μg/g) in propofol bulk drug. Stressed tests proposed that oxidative degradation, photolytic degradation, and heat are the main causes for the formation of degradation products in propofol.     

Electropolymerization of single‐walled carbon nanotubes composited with polypyrrole as a solid‐phase microextraction fiber for the detection of acrylamide in food samples using GC with electron‐capture detection

We developed a solid‐phase microextraction coupled to GC with electron‐capture detection method for the detection of acrylamide in food samples. Single‐walled carbon nanotubes and polypyrrole were electropolymerized onto a stainless‐steel wire as a coating, which possessed a homogeneous, porous, and wrinkled surface, chemical and mechanical stability, long lifespan (over 300 extractions), and good extraction efficiency for acrylamide. The linearity range between the signal intensity and the acrylamide concentration was found to be in the range 0.001–1 μg/mL, and the coefficient of determination was 0.9985. The LOD, defined as three times the baseline noise, was 0.26 ng/mL. The reproducibility for each single fiber (n = 6) and the fiber‐to‐fiber (n = 5) repeatability prepared in the same batch were less than 4.1 and 11.2%, respectively.     

An interesting two‐phase solvent system and its use in preparative isolation of aconitines from aconite roots by counter‐current chromatography

Two‐phase solvent system plays crucial role in successful separation of organic compounds using counter‐current chromatography (CCC). An interesting two‐phase solvent system, composed of chloroform/ethyl acetate/methanol/water, is reported here, in which both phases contain sufficient organic solvents to balance their dissolving capacities. Adjusting the solvent system to get satisfactory partition coefficients (K values) for target compounds becomes relatively simple. This solvent system succeeded in sample preparation of aconitine (8.07 mg, 93.69%), hypaconitine (7.74 mg, 93.17%), mesaconitine (1.95 mg, 94.52%) from raw aconite roots (102.24 mg, crude extract), benzoylmesaconine (34.79 mg, 98.67%) from processed aconite roots (400.01 mg, crude extract), and yunaconitine (253.59 mg, 98.65%) from a crude extract of Aconitum forrestii (326.69 mg, crude extract).     

Comparison of different sample pre‐treatments for multi‐residue analysis of organochlorine and pyrethroid pesticides in chrysanthemum by gas chromatography with electron capture detection

The widespread use of insecticides in Chinese herbal medicines has created a compelling need for the development of a multiresidue analytical method to help assure herbs safety. The operating variables affecting the performance of the multiresidue analysis of 34 organochlorine and 12 pyrethroid pesticides in chrysanthemum, a widely used kind of Chinese herbal medicines, were evaluated. Three different extraction solvents including n‐hexane and its mixtures with acetone and petroleum ether were compared, and n‐hexane was found to be an appropriate option. A combination of gel permeation chromatography and SPE was selected as the optimum cleanup, in comparison with dispersive SPE, or the two former methods alone. The determination of the 46 pesticide residues in the spiked chrysanthemum samples was performed by GC with electron capture detection. The average recoveries ranged from 71.3 to 102.6% with RSDs of 1.4–15.7% for all of the pesticides. The LOQs were in the range of 0.0015–0.2 mg/kg, while the LODs were between 0.0005 and 0.1 mg/kg. The satisfactory accuracy, and precision, in combination with a good separation and few interferences, have demonstrated the strong potential of this technique for its application in chrysanthemum analysis.