“宠物毒粮”中的假冒蛋白质——三聚氰胺

详细介绍了三聚氰胺的结构、制备和性质;从各个角度分析了它的毒性,分析了它对人和动物的危害。     

Confocal Raman Spectroscopy – Applications on Wood,Pulp, and Cellulose Fibres

The manifold possibilities using dispersive Raman spectroscopy along the production chain from wood to cellulose fibre are presented here: The distribution of the lignin, cellulose, and added resins in the wood cell; additives inside regenerated cellulose fibres; their accessibility and reactivity. On-line measurements during the phase transition of magnesium sulphite -hexahydrate into -trihydrate are performed in a stirring vessel.     

Integrated photografted molecularly imprinted polymers with a cellulose acetate membrane for the extraction of melamine from dry milk before HPLC analysis

In this study, a new separation technique based on membrane extraction is described for the determination of melamine in dry milk. The water‐compatible cellulose acetate membrane, which is photografted by melamine imprinted nanospheres, was prepared by placing the membrane into the polymerization solution containing methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as cross‐linker, acetonitrile as porogen, and melamine as the template molecule. The characterization of the polymeric membrane was performed by Fourier transmission infrared spectroscopy and scanning electron microscopy. This integrated composite membrane was used as a solid‐phase extraction medium for the extraction of melamine from dry milk samples. Various parameters affecting the extraction efficiency of the membrane were evaluated. The results showed higher binding capacity for melamine imprinted membranes in comparison with the nonimprinted membranes. High‐performance liquid chromatography analysis showed that the extraction of melamine from dry milk by the photografted cellulose acetate membrane had a linear calibration curve in the range of 0.02–11.80 μg/mL with an excellent precision of 2.73%. The limit of detection and quantification of melamine was 0.007 and 0.020 μg/mL, respectively. The recoveries of melamine were in the range of 88.7–94.8%.     

Exploring Redox Behavior of Neutral pH Active Poly(melamine) and its Electrocatalytic Origination towards NADH Detection

We report here in detail the redox properties and catalytic origination of poly(melamine). Gradual change in redox behavior of the monomer from polymer is explained by grafting monomer and different amounts of polymer on screen printed carbon electrode. The redox peak of the poly(melamine) is pH‐dependent with a slope of ?60 mV/pH, representing a Nernstian type proton‐coupled electron‐transfer process. Catalytic origination from the ? NH‐NH? bond formed in polymer is proved using NADH as a probe. This polymer is effective to catalyze NADH oxidation with a wide linear range of 1 μM–10 mM and a detection limit (S/N=3) of 0.67 μM. Most importantly, unlike most neutral pH active polymer dyes, it shows high stability even after 15 days.     

Designing semiencapsulation based covalently self‐healable poly(methyl methacrylate) composites by Atom Transfer Radical Polymerization

Self‐healable poly(methyl methacrylate) (PMMA) composites were fabricated with embedded glycidyl methacrylate (GMA) encapsulated poly(melamine‐formaldehyde) microcapsules. The matrix polymers were synthesized via Atom Transfer Radical Polymerization using two different initiators; one linear and another hexafunctional. As the so prepared polymer matrix retains living characteristics, it can initiate a healing reaction when the encapsulated monomer reaches the matrix due to formation or extension of a crack and thus healing the system covalently. The effect of number of initiating functionality on healing characteristic was studied using both linear and 6‐armed star PMMA having same targeted molecular weight. Both the systems were able to restore 100% original fracture toughness after healing. However, the polymer matrix prepared by hexafunctional initiator restored the fracture toughness much faster than that of the linear polymer matrix. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1842–1851     

Hydrogen-bonding recognition-induced aggregation of gold nanoparticles for the determination of the migration of melamine monomers using dynamic light scattering

The migration of melamine monomers from food contact materials has aroused particular attention since the 2008 melamine-tainted milk scandal in China. However, the determination of melamine monomer’s migratory quantity (MMMQ) has remained an open question because of the complex sample pretreatment and the low sensitivity. Based on the hydrogen bonding interaction between DNA thymine and melamine, this paper described a simple and rapid method focusing on the measurement of MMMQ from melamine tableware by gold nanoparticles (GNPs) and dynamic light scattering (DLS). With the presence of probe DNA (p-DNA), the GNPs were stable in NaCl solution (0.06 M), whereas they became aggregated when the p-DNA hybridized with melamine. The change in the hydrodynamic diameter of GNPs could be detected by DLS technology. Under the optimal conditions, the average diameter increased linearly with the concentration of melamine over the range from 5.0 to 320.0 μg L⁻¹, and showed a detection limit of 2.0 μg  L⁻¹ (3σ/slope). The MMMQ was investigated within a range from 6.00 × 10⁻⁴ to 2.58 × 10⁻¹ mg dm⁻² (n ≥ 3) in four different food simulants at different temperatures and time points. The results suggest that the DLS method has great potential in the analysis of the migration of melamine monomers.     

Effects of melamine polyphosphate and halloysite nanotubes on the flammability and thermal behavior of polyamide 6

Melamine polyphosphate (MPP) and halloysite nanotubes (HNT) were introduced to polyamide 6 (PA6) by melt blending in order to improve the fire resistance. PA6 composite containing 12% flame retardants with good spinnability was obtained. The flammability of PA6 composite was characterized by limiting oxygen index (LOI), UL‐94 vertical burning and cone calorimeter (CONE) tests. The results indicated that the LOI value could reach 24.0 vol.% and UL‐94 rating could achieve V2 level at the presence of 12% flame retardants. CONE data demonstrated that peak heat release rate was significantly reduced from 554 kW/m² of neat PA6 to 368 kW/m² of the sample containing flame retardants. Thermal analysis indicated that the thermal stability and char formation were improved by the presence of flame retardants. The morphology of residue char was characterized by scanning electron microscopy; and it suggested that a network‐structured protective char layer had been formed. The possible synergism between MPP/HNT and their flame retardant mechanism was also analyzed and discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

新型多功能三溴三聚氰胺催化剂催化醇甲酰化和乙酰化反应MaryamHajjami,ArashGhorbani-Choghamarani,ZahraKaramshahi,MasoomehNorouzi简

Tribromo melamine has been found to be an efficient and green organocatalyst for the acetylation and formylation reactions of alcohols with acetic anhydride and ethyl formate at room temperature and under mild reaction conditions.     

硝酸活化三聚氰胺前驱体对g-C3N4结构和可见光催化性能的影响

为缩短e-和h+的迁移途径而改善g-C3N4易发生光生载流子复合的缺陷,采用不同物质的量浓度的HNO3活化三聚氰胺前驱体,通过形成质子化氨基基团,制备了一系列x-HNO3-g-C3N4(x=1,2,3,4,5 mol·L^-1)光催化剂。采用N2物理吸附-脱附、X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、荧光光谱(PL)、紫外-可见漫反射光谱(UV-Vis DRS)、瞬态光电流响应谱(TCS)和电化学阻抗图谱(EIS)等测试手段对上述光催化剂进行了表征分析,以考察催化剂的结构与其光催化性能之间的影响作用规律。以罗丹明B(RhB)为模拟染料污染物,分别以x-HNO3-g-C3N4和直接煅烧三聚氰胺得到的g-C3N4为光催化剂,进行了可见光催化降解活性差异性能测试研究。由实验结果可知:3 mol·L^-1-HNO3-g-C3N4的光催化活性最高,相较于直接煅烧三聚氰胺得到的g-C3N4,在60 min内,其可将RhB的降解率从38%提高到99%。将3 mol·L^-1-HNO3-g-C3N4催化剂循环使用4次后,催化效果仍为99%。这是因为三聚氰胺前驱体经HNO3活化后,可使经热聚合制备而成的g-C3N4产品具有较高的聚合度,从而得到具有大比表面积的多层g-C3N4;此外,PL结果证明其荧光强度明显降低,而使载流子寿命获得了显著提高;EIS结果表明其载流子传输能力有了明显的增强,从而提高了g-C3N4的光催化活性。