Developing an on-line derivatization of FAs by microwave irradiation coupled to HPLC separation with UV detection

The development of analytical methods for routine simultaneous identification and quantification of carboxylic fatty acids (CFAs) are required in different fields, such as, pharmaceutical cosmetics, food products and formulations of water–microemulsion–oil systems. Determination of CFAs has been developed mainly by gas chromatography (GC). As an alternative to GC, liquid chromatography (LC) has better sensitivity and selectivity. However, most CFAs show no useful absorption in ultraviolet–violet (UV–Vis) region, one of the more used detection technique in high-performance liquid chromatography (HPLC). In order to allow the use of UV–Vis detection, the use of pre-column derivatization has been reported to increase sensitivity and selectivity. Therefore, establishment of a simpler and faster on-line method with complete separation is needed for the screening of large numbers of samples. 2,4-Dinitrophenylhydrazine (2,4-DNPH.), benzoil chloride (BC), and phenylhydrazine (PH) were used for derivatization of different FAs by microwaves radiation (MW). After the on-line derivatization, products were separated and quantified by HPLC. Reactor coil was placed inside of microwaves oven at 450 W. Parameters as flow, amount of reagents, irradiation time, and chromatographic conditions were optimized. The continuous analysis using the MW–HPLC–UV system provided high sensitivity and reduced both the amount of reagent used and the analysis times. This proposed method can be used for the routine analysis of FAs contained in water–microemulsion–oil systems, to quantify the total acid fraction in each phase.     

Microstructure–conductivity relationship in Gd- and Sm-doped ceria-based electrolytes prepared by the acrylamide sol–gel-related method

We have prepared pure electrolytes of Ce_0.8Gd_0.2O_1.9 (CGO) and Ce_0.8Sm_0.2O_1.9 (CSO), useful for SOFCs, by a sol–gel-related technique like the acrylamide method. This method consists of preparing a solution from the single oxides followed by gelation. Then, the combustion or decomposition of the organic molecules is initiated, producing nanometric calcined powders of the above-mentioned compounds. Thermal treatments were optimized in order to obtain good electrochemical properties of the electrolytes. We have observed that the synthesis temperature to obtain the pure phase is lower for the sol–gel samples than for the pellets prepared by solid-state reaction, and the final density is higher. The microstructure and composition of the powders were characterized by TEM, SEM, and EDX analysis. The electrical properties of the electrolytes were measured by impedance spectroscopy at different temperatures and oxygen partial pressures.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

清除试剂在液相组合化学中的应用

综述了近年来清除试剂在液相组合化学中的应用,并介绍了一些采用清除试剂对液相化合物库进行分离和纯化的实例。对清除试剂进行了分类,各类清除试剂参与的液相反应以及被清除的非目标产物类型也作了相应的介绍。     

离子色谱法测定洗涤用品中的氮川三乙酸盐

研究并建立了洗涤用品中氮川三乙酸盐(NTA)的离子色谱测定方法。将洗涤用品样品用超纯水稀释200~500倍,置于磁力搅拌器上搅拌至完全溶解,样品提取液依次过尼龙滤膜和OnGuardII RP固相萃取柱。滤液采用离子色谱-抑制电导检测法分析测定,以IonPac AS11阴离子交换色谱柱分离,以KOH溶液为淋洗液进行梯度洗脱,ASRS-400阴离子型抑制电导检测,外标法定量。方法的线性范围为0.02~10μg/mL,相关系数为0.9998,对氮川三乙酸盐定量限为20 mg/kg,液类洗涤用品在低、中、高3种加标水平的回收率为90.9%~103.2%,相对标准偏差为1.9%~4.1%;粉类产品在低、中、高3种加标水平的回收率为89.3%~105.1%,相对标准偏差为4.1%~6.7%;皂类产品在低、中、高3种加标水平的回收率为96.9%~115.1%,相对标准偏差为2.3%~4.2%。     

液体闪烁计数法测定生物塑料中生物基含量

研究并建立了液体闪烁计数法测量生物塑料中生物基含量。首先将生物塑料样品充分燃烧,通过碳的转移与固定,最终催化合成液态苯。通过液体闪烁计数器对液体苯中的放射性核素14C衰变进行计数,从而计算生物塑料样品中生物基的含量。生物塑料样品加标回收率为98.5%~101%,相对标准偏差为0.2%。方法可用于生物塑料中生物基含量检测。     

铁催化2-烯基氮杂芳烃的绿色合成

以廉价、低毒的醋酸亚铁为催化剂,在三氟乙酸助催化下,2-甲基氮杂芳烃与芳香醛经过加成与脱水反应,直接选择性合成具有生物活性的反式2-烯基氮杂芳烃化合物,水是唯一副产物.该合成方法催化剂用量少,后处理方便,产率高,选择性高,底物适用范围广.治疗哮喘药顺尔丁中间体(E)-3-[2-(7-氯-2-喹啉基)乙烯基]苯甲醛(3v)的克级合成展现了该方法的应用前景.     

Thermal properties and kinetics of new-generation posterior bulk fill composite cured light-emitting diodes

In this study, the thermal behavior in terms of glass transition (T _g), degradation, and thermal stability of four commercial new-generation posterior bulk fill composites (Surefill SDR, Dentsply; Quixfill, Dentsply; Xtrabase, Voco; and Xtrafill, Voco) activated by light-emitting diodes (LEDs) was analyzed by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The activation energies (E _a) for the decomposition of the dental resins were calculated based on the Kissinger and Doyle kinetic models from the peaks of the endothermic curves obtained when the specimens were heated at four different temperatures (5, 10, 15, and 20 °C min^?1) during DSC. The results show that the Xtrabase composite displayed the highest T _g (120 °C at a 5 °C min^?1 heating rate) and E _a (157.64 kJ mol^?1) values associated with thermal degradation from the main chain of the polymer.     

Functional copolymer/organo‐MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA‐alt‐1‐octadecene)‐g‐PLA layered silicate nanocomposites with nanoporous core–shell morphology

Novel bioengineering functional copolymer‐g‐biopolymer‐based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L‐lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1‐octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo‐MMT clay (reactive ODA‐MMT and non‐reactive DMDA‐MMT) complexes as nanofillers and tin(oct)₂ as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT‐IR spectroscopy, X‐ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA‐DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro‐ and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H‐bonding and self‐organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride‐containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer‐g‐biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.     

On the Dual Phosphorescence of Xanthone and Chromone in Glassy Hydrocarbon Hosts

Trace quantities of hydrogen‐bonding impurities in otherwise highly purified and dried glassy hydrocarbon matrices at 77 K can modify the relative triplet state energy levels, and hence the photophysical properties of two aromatic ketones, xanthone and chromone, to the extent that the intrinsic spectroscopic properties are obscured. The intrinsic spectroscopic properties of each are revealed in multicrystalline n‐alkane Shpol'skii matrices, and also can be observed in rigorously purified and dried hydrocarbon glasses at 77 K. The extreme sensitivity to stoichiometric, and even substoichiometric quantities of hydrogen‐bonding impurities arises from the near‐degeneracy of the two lowest‐lying triplet states, and the sensitive nature of the n→π* blueshift phenomena to specific hydrogen‐bonding interactions.     

固相萃取-气相色谱-串联质谱法测定乳胶儿童用品中15种N-亚硝胺及其前体物的迁移量

建立了同时测定乳胶儿童用品中15种N-亚硝胺及其前体物迁移量的固相萃取-气相色谱-串联质谱(SPEGC-MS/MS)分析方法。以人工唾液作为迁移模拟物,以Chromabond Easy固相萃取柱(填料的主要成分是极性修饰的聚乙烯-二乙烯基苯共聚物)对迁移液中的N-亚硝胺分析物进行净化,采用HP-5 MS UI色谱柱分离,MS/MS在多反应监测模式下进行定性及定量分析。15种N-亚硝胺在5~2 000μg/L范围内呈良好的线性关系,相关系数均大于0.998;方法定量限(S/N=10)为0.625~12.50μg/kg,低于欧盟2 009/48/EC指令的限量要求。在低、中、高3个添加水平的回收率为53.8%~116.2%、52.7%~105.1%和49.5%~102.9%;日内精密度分别为1.3%~14.0%(n=6),日间精密度为1.6%~7.6%(n=4)。采用本方法对婴儿奶嘴样品和气球样品进行了测定,其中4件奶嘴和7件气球样品中检出亚硝胺及其前体物,奶嘴和气球中N-亚硝胺的总检出含量分别为0.049 9~0.126mg/kg和0.515~41.2 mg/kg;N-亚硝胺前体物总检出量分别为0.026 4~0.030 0 mg/kg和0.187~12.5mg/kg。