阴极催化剂Sm1.5Sr0.5MO4 (M＝Ni, Co, Fe)在低温常压下合成氨

利用溶胶—凝胶法制备了复合氧化物Sm1.5Sr0.5MO4 (M＝Ni, Co, Fe)(SSM),并利用XRD和SEM等对样品进行表征。用Nafion膜作电解质、以SSM作为阴极、Ni-SDC金属陶瓷为阳极、银-铂网做集流体组成单电池,在温度为25℃～100℃的低温常压下以干燥氮气和湿的氢气为原料进行电化学合成氨气测定,同时研究了影响氨合成的关键因素,确定了合适的工作温度,实验结果表明,最高氨产率可达到1.05×10-8mol·s-1·cm-2。     

Optimization of a microwave-assisted extraction of secondary metabolites from crustose lichens with quantitative spectrophotodensitometry analysis

A focused and rapid microwave-assisted extraction (MAE) process was carried out and optimized for secondary metabolites from crustose lichens using Taguchi experimental design and quantitative analysis on TLC by a Camag^® spectrophotodensitometer. The procedure was improved by quantitative determination of norstictic acid (NA), a common depsidone isolated from Pertusaria pseudocorallina (Sw.) Arn. Various experimental parameters that can potentially affect the NA extraction yields including extraction time, irradiation power, volume and the percentage of tetrahydrofuran (THF) were optimized. Results suggest that THF percentage and solvent volume were statistically the most significant factors. The optimal conditions were determined as follows: THF level of 100%, solvent volume of 15 mL, microwave power of 100 W and extraction time of 7 min. Compared to the reflux method, MAE showed a drastic reduction of extraction time (7 min vs. 3 h) and solvent consumption (15 mL vs. 30 mL). The NA in total yield was 90% using the two methods. The optimal conditions were applied to other crustose lichens, Aspicilia radiosa, Diploicia canescens and Ochrolechia parella for the extraction of NA, diploicine (DP) and variolaric acid (VA), with 83%, 90% and 95% of recovery, respectively.     

Simple mercury fractionation in biological samples by CV AAS following microwave-assisted acid digestion or TMAH pre-treatment

A simple and reliable method to determine total and inorganic mercury in biological certified reference material (CRM) by cold vapor atomic absorption spectrometry (CV AAS) is proposed. After the CRM treatment at room temperature with tetramethylammonium hydroxide (TMAH), inorganic mercury is determined by CV AAS. Total mercury is measured by the same technique, after sample acid digestion in a microwave oven. Organic mercury, basically methylmercury, is obtained by difference. In both procedures, the quartz tube is kept at room temperature. By means of analysis of the following reference materials: pig kidney, lobster hepatopancreas, dogfish liver and mussel tissue, it was clear that the difference between the total and inorganic mercury concentrations agrees with the methylmercury concentration. Only one calibration curve against aqueous standards in acidic medium was carried out for both procedures. The concentrations obtained by both procedures are in agreement with the certified values according to the t-test at a 95% confidence level. The relative standard deviations were lower than 3.0% for digested CRM and 6.0% for CRM treated with TMAH for most of the samples. The limits of detection in the samples were 0.02 µg g^{− 1} and 0.04 µg g^{− 1} for inorganic and total Hg, respectively, since the sample mass for total mercury was half of that for inorganic mercury determination. Simplicity and high efficiency without using chromatographic techniques are some of the qualities of the proposed method, being adequate for fractionation analysis of mercury in biological samples.     

Microwave-assisted extraction for qualitative and quantitative determination of brominated flame retardants in styrenic plastic fractions from waste electrical and electronic equipment (WEEE)

A fast method for the determination of brominated flame retardants (BFRs) in styrenic polymers using microwave-assisted extraction (MAE) and liquid chromatography with UV detection (HPLC-UV) was developed. Different extraction parameters (extraction temperature and time, type of solvent, particle size) were first optimised for standard high-impact polystyrene (HIPS) samples containing known amounts of tetrabromobisphenol A (TBBPA) and decabromodiphenyl ether (Deca-BDE). Complete extraction of TBBPA was achieved using a combination of polar/non-polar solvent system (isopropanol/n-hexane) and high extraction temperatures (130 °C). Lower extraction yields were, however, obtained for Deca-BDE, due to its high molecular weight and its non-polar nature. The developed method was successfully applied to the screening of BFRs in standard plastic samples from waste electrical and electronic equipment (WEEE); TBBPA could be fully recovered, and Deca-BDE could be identified, together with minor order polybrominated diphenyl ether (PBDE) congeners.     

Improved methodologies for synthesis of prenylated xanthones by microwave irradiation and combination of heterogeneous catalysis (K10 clay) with microwave irradiation

Eleven prenylated xanthone derivatives (4-9, 11-15) have been synthesized for the first time by the microwave irradiation method. Prenylation of the xanthone building blocks 1 and 2 with prenyl bromide in alkaline medium, using microwave irradiation, gave the oxyprenylated xanthones 4 and 6, as major products in high yields, as well as diprenylated by-products (5, 7, 8, and 9) in very low yields. Microwave irradiation of oxyprenylated xanthones 4 and 6 furnished three new Claisen rearranged products (11, 14, and 15), as well as the previously described dihydrofuranoxanthones (12, 13). Furthermore, three new (19, 20, 21) and three previously described (16, 17, 18) dihydropyranoxanthones have also been prepared by a one-pot synthesis from xanthones 1, 2, and 3, using Montmorillonite K10 clay as a heterogeneous catalyst and a combination of Montmorillonite K10 clay with microwave irradiation in various conditions. The presence of solvent and the type of the clay (commercial or dry) were found to have a strong influence on the product yields. This is the first report of using these methodologies for the synthesis of dihydropyranoxanthone derivatives. The structures of the prenylated xanthones obtained were established by IR, UV, HRMS, and NMR (¹H, ¹³C, HSQC, and HMBC) techniques.     

The microwave-assisted synthesis and characterization of novel, octakis(2-hydroxyethoxy)resorcinarene bridged polymeric metallophthalocyanines

The new metallophthalocyanine (Zn, Cu, Ni, Co) polymers containing 4,6,10,12,16,18,22,24-octakis(2-hydroxyethoxy)-2,8,14,20-tetramethylresorcinarene are described. Firstly, 4,6,10,12,16,18,22,24-octakis(2-hydroxyethoxy)-2,8,14,20-tetramethylresorcinarene compound (1) was synthesized by treating resorcinarene with 2-chloroethanol under microwave irradiation. Then, tetrakis(4,5-bis(2-hydroxyethoxy))phthalonitrile substituted resorcinarene compound (2) and octakis(4-(2-hydroxyethoxy))phthalonitrile substituted resorcinarene compound (3) were synthesized by treating compound (1) with 4,5-dichloro-1,2-dicyanobenzene and 4-nitro-1,2-dicyanobenzene, respectively, under microwave irradiation. The chlorides Cu (II), Ni (II), Co (II), were employed in order to synthesize the corresponding metallophthalocyanine polymers (2b–d and 3b–d) and Zn(CH₃COO)₂ was used for the preparation of zinc phthalocyanine polymers (2a and 3a). All products were synthesized by microwave-assisted synthesis method. The structures were characterized by elemental analyses, ¹H NMR, ¹³C NMR, UV–Vis and FTIR spectroscopy.     

原子吸收法测定枸杞子矿物质元素的三种前处理方法比较

采用干灰化法、HNO₃-H₂O₂湿法消解法和HNO₃-HClO₄湿法消解法分别处理枸杞子样品,利用原子吸收光谱法测定各组样品中Na,K,Ca,Mg,Fe,Cu,Zn,Ni,Pb,Cd十种元素的含量,探讨简单、快捷、准确地测定枸杞子中矿物质元素的前处理方法。结果表明：干灰化法的回收率范围为89.88%～102.15%,标准偏差(RSD)<3.037% ;HNO₃-H₂O₂湿法消解法的回收率范围为92.34%～103.21%,标准偏差(RSD)<2.751%;HNO₃-HClO₄湿法消解法的回收率范围为94.52%～102.10%,标准偏差(RSD)<2.496%;三种方法均具有较好的准确度和精密度,但相对于干灰化法和HNO₃-H₂O₂湿法消解法,HNO₃-HClO₄湿法消解法回收效果较好,精密度更高。HNO₃-HClO₄湿法消解法测得Na, K, Ca, Mg元素含量的平均值高于干灰化法和HNO₃-H₂O₂湿法消解法,差异有统计学意义(p<0.05)。此外,HNO₃-HClO₄体系湿法消解法耗时短、消耗试剂量少、消解完全。因而,HNO₃-HClO₄体系湿法消解法可作为原子吸收光谱法测定枸杞子矿物质元素含量较好的前处理方法。     

程序控温石墨消解-氢化物原子荧光光谱法测定植物中痕量硒

探讨了硒测定的几种预处理方法,采用一种程序控温的石墨消解系统来消化处理柑橘叶、茶叶、灌木叶、圆白菜、大米五种代表性的植物标准样品。详细研究了这类植物样品前处理方法中消解液用量、消解温度以及消解时间对植物样品中硒提取效果的影响;优化了氢化物发生-原子荧光光谱法(HG-AFS)的仪器参数条件;在氢化物反应条件中重点考察了还原剂KBH₄浓度和酸度(HCl)对硒测定的影响,不仅考虑了载流HCl浓度的影响,还从样品HCl浓度就酸度对硒测定影响作了进一步细致研究,从而建立了石墨消解-氢化物发生原子荧光光谱法测定这类植物样中痕量硒的最佳测定方法。结果显示：该方法中硒加标回收率在87.1%～106.2%,检出限0.018 μg·L-1,精密度RSD＜6.0 %,标准物质的测试结果与参考值均相吻合;在0～10 μg·L-1低标范围内和在0～100 μg·L-1 高标范围内,荧光值与硒浓度均呈线性相关,相关系数分别为r=0.999 9和=0.999 7。因此该方法具有线性范围宽、灵敏度高、检出限低,稳定性好的显著特点,尤其适合如柑橘叶、茶叶、灌木叶、圆白菜、大米等这类批量植物样品硒的痕量分析,且该方法操作简便安全,实用性强,仪器成本低,所用试剂毒性小,可作为一般实验室的常规分析方法。     

Global attractability and permanence for a new stage-structured delay impulsive ecosystem

In this paper, a new stage-structured delay ecosystem with impulsive effect is formulated and some dynamical properties of this system is investigated.By using comparison theorem and the stroboscopic technique, we prove the existence of the predator-extinction periodic solution of this system and obtain some sufficient conditions to guarantee the global attractivity of the prey-extinction periodic solution. In the final, we also obtain the permanence of this system. It should be pointed out that the new mathematical method used in this paper can also be applied to investigate such other ecosystems corresponding to both impulsive and delay differential equations.     

微波消解/ICP-MS法测定烟草中微量元素含量

采用2 mL 50% HNO₃和1 mL 47% H₂O₂作为消解体系,最终消解液酸度在2%左右对烟草样品进行微波消解,标准溶液采用2% HNO₃稀释,添加Ge和Rh内标元素,直接进行ICP-MS分析。此方案避免采用浓酸,可省去赶酸或稀释的繁琐步骤,延长仪器相关部件使用寿命,消除由于样品溶液与标准溶液酸度差别较大带来的误差。测试考察了烟草中30种微量元素,给出7个烟草产区样品中8种微量元素的测定结果。方法检出限为0.006～1.133 ng·mL-1,相对标准偏差0.90%～5.66%,Cu和Y回收率93%～102%。结果表明,文章所提出的微波消解方法适用于烟草中多种微量元素的同时测定,烟草样品微量元素含量与烟草产地、类别有紧密联系。