Recognition-improved monolayer formation on air-water interface

Molecular recognition mechanism was introduced into the monolayer formation of two barbituric derivatives, B1 and B2, on a series of melamine derivatives containing water sub-phase. The recognition pattern was found that each barbituric(or melamine) group forms 3-fold H-bonds on its two edges, respectively, with two of its neighboring melamine(barbituric) cores in the ratio of 1:1 on air-water interface. The area per molecule in this pattern is about 60-65 A2 for both Bl and B2. Such recognition improves the monolayer formation of Bl by increasing the collapse pressure around 20 mN/M and modulates the intermolecular distance of B2 in monolayer. These effects should be quite meaningful for both theoretical research and practical application of Langmuir-Blodgett films, especially.     

三聚氰胺分子印迹光子晶体水凝胶膜传感器的制备及应用

该文将光子晶体与分子印迹技术结合，制备了分子印迹光子晶体水凝胶膜（MIPHs）作为光学传感器，用于样品中三聚氰胺的快速识别检测。以三聚氰胺为模板分子，通过垂直沉降自组装、填充聚合、去除模板3个步骤，制备得到了反蛋白石结构的三聚氰胺MIPHs。扫描电子显微镜的形貌表征表明，MIPHs具有高度有序的三维大孔结构。该MIPHs作为光学传感器可以将三聚氰胺的分子特异识别过程转换成光学信号，在对目标分析物分析时具有选择性高、响应快、灵敏度高的优点。此外，可以根据MIPHs的颜色变化利用图像软件分析或裸眼识别的方式实现目标分析物快速识别。实验结果表明，在最优条件下，三聚氰胺浓度为10^-11~10^-6mol/L时，MIPHs的布拉格衍射峰位移从563 nm红移到608 nm，而对三聚氰胺的结构类似物没有明显响应。     

氨基聚酯树脂固化过程的FTIR跟踪

用FTIR内标法跟踪氨基聚酯树脂的固化过程,选取815cm~(-1)的三嗪环面外振动峰作内标峰,913cm~(-1)处的甲氧基变形振动峰和3500cm~(-1)左右的羟基伸缩振动峰为特征吸收峰。结果表明,随着固化的进行,涂膜的羟基、甲氧基和羧基递减,醚键和羰基递增,说明固化过程是以交联反应为主,伴有自缩合反应和酯化反应的复杂过程。     

EuPtP,Eu1–xGdxPtP und Eu0,5Sr0,5PtP: Strukturen und Zwischenvalenz

EuPtP, Eu_1–xGd_xPtP, and Eu_0.5Sr_0.5PtP: Structures and Intermediate Valence EuPtP with a strong temperature dependence of the Eu-valency undergoes two first order phase transitions at 235 K (α-/β-form) and 190 K (β-/γ-form). The compound crystallizes in a modified Ni₂In-type structure, the P-atoms (α-, β-EuPtP) and the Pt-atoms too (γ-EuPtP) are shifted towards one of two Eu-layers. Compounds of the series Eu_1–xGd_xPtP and Eu_0.5Sr_0.5PtP crystallize in the same type of structure as α- or β-EuPtP, but don't undergo with x > 0.05 the above mentioned phase transitions. They were studied by L_III—X-ray absorption and susceptibility measurements: The valence of Eu shows roughly the same temperature dependence as in EuPtP, only one magnetic order transition was found. The structural details and the behaviour of these compounds are discussed with a domain picture.     

氧化石墨烯色谱固定相的制备及其在食品中三聚氰胺分析中的应用

以N,N-二环己基碳二亚胺为偶联剂,利用氧化石墨烯表面的羧基与氨基化硅球表面的氨基反应合成了一种氧化石墨烯键合硅球色谱固定相,通过扫描电镜和拉曼光谱对其进行表征,并考察了极性小分子在柱上的色谱行为。与氨基化硅球固定相相比,在相同的色谱条件下,三聚氰胺、双氰胺等氨基化合物的保留因子明显提高,且该固定相在亲水模式下对氨基化合物具有良好的保留性能,将其作为分析柱用于鸡蛋和牛奶中三聚氰胺的分析。该方法在0.2~50μg/m L范围内线性良好,相关系数(r)为0.999 9,定量下限为0.87mg/kg。在1,2,10 mg/kg加标水平下的回收率为84.7%~93.9%,相对标准偏差为4.1%~6.3%。     

三聚氰胺三聚硫氰酸盐的合成

以三聚氰胺和三聚硫氰酸为原料合成了一种新型含硫三聚氰胺基阻燃剂——三聚氰胺三聚硫氰酸盐(MSA),其结构和热性能经1H NMR,13C NMR,FT-IR,元素分析和TGA表征。确定了合成MSA的最优工艺条件为:去离子水为溶剂,三聚硫氰酸和三聚氰胺摩尔比为1∶1,反应时间为3 h。TGA分析表明:MSA失重5%时,温度为308.8℃,600℃时分解基本完全,残碳率为0.86%。     

Primary amide-functionalized cyclotricatechylene covalent organic frameworks membrane for efficient enrichment of melamine and its derivatives in migration solution of food contact materials

A highly chemically stable primary amide-functionalized cyclotricatechylene covalent organic framework was synthesized by an irreversible reaction and a post-synthetic modification. It possessed a rod-like morphology and exhibited strong solvent stability owing to the polyether bonds. The material showed good adsorption performance for melamine and its derivatives and adsorption mechanism was investigated by molecular simulations. The adsorbent was coated on the nylon-66 membrane to prepare the enrichment membrane. Under optimized conditions, an in-syringe membrane-based extraction method, combined with ultra-high performance liquid chromatography-tandem mass spectrometry was developed for the analysis of melamine and six melamine derivatives in the migration solution. A good linearity was obtained with correlation coefficients ranging from 0.9924 to 0.9995. The limits of detection were 1–200 ng/L and the limits of quantification were 3–500 ng/L. This method was successfully applied to the migration solution of sushi bamboo rolling mats with spiked recoveries of 73.2%–115% and relative standard deviations of 0.9%–9.9%. This work shows a practical and perspective approach for the efficient enrichment of food contact material hazards.     

Green dispersive solid-phase microextraction of melamine using crosslinked beta-cyclodextrin with citric acid followed by high-performance liquid chromatography

In this research, a green approach for dispersive solid phase microextraction was introduced for the extraction and determination of melamine in various matrices such as infant formula and hot water in a melamine bowl. In this way, a natural polar polymer called ß-cyclodextrin has been cross-linked with citric acid to create a water-insoluble adsorbent. The extraction was carried out by dispersion of the sorbent into the sample solution. The effective parameters on the extraction efficiency of the melamine, including ion strength, extraction time, sample volume, amount of absorbent, pH, type of desorption solvent, desorption time, and desorption solvent volume were optimized by one variable at a time approach. Under the optimal conditions, the method showed a good linear dynamic range for melamine in the range of 1–1000 μg/L with a coefficient of determination of 0.9985. The obtained limit of detection was 0.3 μg/L. The intra-day and inter-day relative standard deviations (n = 3) were 3.1% and 3.2% respectively. Lastly, this technique was applied to extract and determine the analyte in a melamine bowl and infant formula with acceptable and satisfactory results.     

Hydrogen-bonded Supramolecular Rosette Ribbon Constructed from Melamine with Isophthalic Acid

The new complex of melamine （MA） with isophthalic acid （H2IA）, [（HMA^＋）- （HIA^-）]·2H2O, has been prepared and its structure was characterized by X-ray crystallography. The crystal is of triclinic, space group P^-1 with a = 7.0228（6）, b = 9.1706（8）, c = 12.170（1） A, α = 95.337（2）, β = 105.247（2）, γ = 97.813（2）^o, V = 742.3（1） A ^3, Mr= 328.30, Z = 2, Dc = 1.469 g/cm^3, ;λ = 0.71073 A,μ（MoKa） = 0.121 mm^-1 and F（000） = 344. The structure was refined to R = 0.0389 and wR = 0.1093 for 2513 observed reflections with I 〉 2σ（I）. Melamine dimer and isophthalic acid anion are interlinked by N-H…N and N-H…O hydrogen bonds, resulting in a 1D rosette ribbon in which water molecules and amino groups are self-assembled into quasihexagonal patterns.