Adaptation of the ORAC assay to the common laboratory equipment and subsequent application to antioxidant plastic films

The oxygen radical absorbance capacity (ORAC) method has been adapted to the instrumental laboratory and optimized for the determination of the antioxidant capacity of a novel active packaging. As the ORAC assay requires the monitorization of a reaction at controlled temperature by means of the fluorescence signal decrease over time, specific instrumental is usually necessary. In this work, a common liquid chromatographic device has been adapted to perform the ORAC assay, leaving it accessible to any laboratory. Using this adaptation, five different essential oils have been determined resulting in the following antioxidant order: clove (2.66 g Trolox per gram of essential oil), oregano (2.25), cinnamon (1.93), rosemary (1.66), and ginger (1.47). After incorporating the essential oils to the film, its antioxidant capacity has also been checked and related to the concentration of essential oil as well as the thickness of the active film. The results point out that for the same amount of essential oil incorporated measured as grams per square meter, thicker films have more antioxidant capacity than the thinner and more concentrated ones. Furthermore, the antioxidant capacity found in the films was always higher than expected taking into account the amount of essential oil incorporated. Some likely explanations have been proposed, leading to the improvement of the antioxidant film under development.     

基于DMD的数字全息显示及其再现像质增强

采用DMD作为空间光调制器构建了一套数字全息显示系统.分析了数字全息图光学再现中影响再现图像质量的因素,提出了一种采用频域滤波重建高条纹对比度滤波全息图来改善其光学再现图像质量的新方法.采用信噪比及图像亮度作为评价参量,对原始全息图和滤波全息图的数值再现像进行定量分析表明,滤波后全息图的再现像质量明显优于原始全息图的再现像.基于DMD数字全息显示系统的光学再现实验也验证了理论分析结果.     

Study of multilayer packaging delamination mechanisms using different surface analysis techniques

Multilayer packaging, consisting of different layers joined by using an adhesive or an extrusion process, is widely used to promote different products, such as food, cosmetics, etc. The main disadvantage in using this form of packaging is the delamination process. In this work, different surface techniques (X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy) are used to analyse the delaminated surfaces in order to study the mechanisms that cause delamination of multilayer packaging. According to our results, the reaction of migrated molecules with adhesive-aluminium bonds is the main cause of the chemical delamination process. In contrast, the delamination of extruded materials would seem to be caused by the breaking of Van der Waals bonds.     

液态乳制品包装材料中VOCs迁移安全性研究

利用顶空/气相色谱-质谱(HS/GC-MS)联用法对百利包、利乐包、塑杯3种乳制品包装材料中的挥发性有机物(VOCs)进行迁移安全性研究。结果表明,平衡温度与保温时间对包装中的VOCs有不同程度的影响。百利包中均含有苯,部分含有异丙醇、乙苯、间/对二甲苯、邻二甲苯,包装材料中VOCs含量为85.64~102.10 ng/cm2;利乐包含有苯、间/对二甲苯、邻二甲苯,部分含有异丙醇、乙酸乙酯、乙酸丁酯、乙苯,包装材料中VOCs含量为54.77~75.16 ng/cm2;塑杯均含有苯,部分含有异丙醇、间/对二甲苯、邻二甲苯,包装材料中VOCs含量为82.63~171.25 ng/cm2。利用迁移模型对乳制品进行研究,得出苯迁移最坏情况为0.885×10-3mg/kg;穿过0.015 cm厚度包装材料所需的时间为76 d,大于其保质期45 d。     

超高效液相色谱-串联质谱法测定食品包装纸中的酚类化合物

建立了食品包装纸中2,4,6-三氯酚、五氯酚、4-氯-3,5-二甲基-苯酚和4-叔-辛基酚的超高效液相色谱-串联质谱(UPLC-MS/MS)分析方法。样品经丙酮超声萃取,Oasis HLB固相柱净化后,用Waters AC-QUITY UPLC C18柱以乙腈和0.05%氨水为流动相进行分离,以负离子模式离子化,在多离子反应监测(MRM)模式下定量检测。在优化实验条件下,2,4,6-三氯酚的线性范围为20~1 000μg.L-1,五氯酚、4-氯-3,5-二甲基-苯酚和4-叔-辛基酚的线性范围为5~1 000μg.L-1,相关系数均大于0.997。4种酚类化合物的检出限为1~10μg.kg-1,定量下限为5~20μg.kg-1,加标回收率为75%~109%,相对标准偏差均不高于12.5%。该方法灵敏度高、操作简单,可用于食品包装纸中酚类化合物含量的快速检测。     

Detection of migration of phthalates from agglomerated cork stoppers using HPLC-MS/MS

Agglomerated stoppers are manufactured from natural cork granules and adhesives. Esters, such as phthalates and adipates, are commonly used in adhesives at concentrations of typically 2-5%. Because of this, and regarding consumer safety, it is necessary to ensure that these compounds do not migrate into the beverage where the cork stopper is used. A reversed-phase high performance liquid chromatography method with tandem mass spectrometry detection is developed for the separation of nine phthalates into 12% ethanol, used as simulant of alcoholic beverages. The chromatographic separation was carried out with a Luna C18 (2) HSTcolumn (50 × 3.0 mm, 2.5 μm) with a gradient elution of water/methanol with 0.1% acetic acid at 300 μL min(-1). The method was validated for four selected phthalates: di-butylphthalate, di-isononylphthalate, di-isodecylphthalate, and butyl-benzyl phthalate, with recoveries ranging between 95% and 112% and intralaboratory precision (RSD) between 5 and 14%, depending on the phthalate. The lowest quantification limit, 0.15 mg kg(-1), was achieved for di-butylphthalate. Nevertheless, in all cases, the limits obtained guarantee the method utility if restriction limits set in Commission Regulation No 10/2011 for plastic materials are taken into account.     

基体匹配校正-顶空-气相色谱法测定食品塑料包装材料中挥发性有机物

采用顶空-气相色谱法测定了食品用软质塑料包装材料中具有代表的10种挥发性有机物(VOC′s),包括甲苯、乙酸乙酯、2,4-戊二酮、2-乙基-1-己醇、1-壬醛、癸烷醛、十二烷醛、癸烷、正辛烷及十二烷,并用基体匹配法抵消了样品本身的基体干扰。从待分析样品(包装膜)裁取约100cm2大小片样置于真空烘箱中,于90℃烘24h,此片试样即可作为空白基质,再加入一定量的上述VOC标准溶液制备校准曲线。另取同一样品一片,剪碎后移入顶空瓶中,立即盖紧,在100℃平衡30min。方法中用HP-INNOWAX色谱柱在20℃～220℃温度区间程序升温,对各VOC进行分离,采用火焰离子化检测器检测。测得10种VOC′s的检出限(3S/N)在0.2～2.0μg.dm-2之间。另测得平均回收率及相对标准偏差(n=6)分别在82.5%～97.6%和0.9%～14.0%之间。     

功率型LED封装用高分子材料的研究进展

随着发光二极管(LED)亮度和功率的不断提高,封装材料已成为制约LED进入照明领域的关键技术之一。对于功率型LED封装材料,要求具有高折射率、高透光率、高导热率、耐紫外、耐热老化、低应力、低吸水率等性能特点。目前LED封装用两大主要高分子材料是环氧树脂和有机硅复合材料。对这两种材料的改性主要集中在折射率、耐老化性、导热性、吸水性和力学性能等方面。脂环族环氧树脂及纳米有机硅复合材料作为高功率LED封装材料具有广阔的发展前景。     

Very high thermal conductivity obtained by boron nitride-filled polybenzoxazine

A thermal conductivity of 32.5 W/mK is achieved for a boron nitride-filled polybenzoxazine at its maximum filler loading of 78.5% by volume (88% by weight). The extraordinarily high conductivity value results from outstanding properties of the polybenzoxazine matrix and the boron nitride filler. The bisphenol-A–methylamine-based polybenzoxazine possesses very low A-stage viscosity which aids in filler wetting and mixing. The filler particles with an average size of ca. 225 μm are large aggregates of boron nitride flake-like crystals. It has bimodal particle size distribution which assists in increasing the particle packing density. This filler–matrix system provides a highly thermally conductive composite due to the capability of forming conductive networks with low thermal resistance along the conductive paths. The SEM picture of the composite fracture surface reveals good interfacial adhesion between the boron nitride filler and polybenzoxazine matrix. Water absorption of the filled systems at 24 h is <0.1% and decreases with increasing filler content.     

非水毛细管电泳-化学发光法测定食品包装材料中酚类环境激素

建立食用包装材料中的双酚A、壬基酚等多种环境激素的非水毛细管电泳-化学发光分析方法.食品包装材料样品浸出物中的双酚A、烷基酚等环境激素经衍生剂DIB-Cl衍生后,经过非水毛细管电泳分离后,分别与过氧草酸酯化学发光反应体系作用,光信号经过光电倍增管接收放大后被检测.以雌二醇(17β-E2)为内标,以相对迁移时间定性,相对发光强度比定量,内标校准曲线法测定样品浸出物中待测物的含量.对影响非水毛细管电泳分离如溶剂组成和比例、电解质浓度、温度、乙酸浓度、电泳电压等条件进行了优化.同时对化学发光体系也进行了优化.4-叔丁基酚、双酚A、4-叔辛基酚、4-壬基酚和四溴双酚 A分别在0.0095～3.0 mg/L, 0.0087～3.0 mg/L, 0.0085～3.0 mg/L, 0.011～3.0 mg/L和0.009～3.0 mg/L范围内线性良好,r＞0.9947.相对迁移时间和相对峰高的RSD分别为0.88%～2.96%和 6.54%～8.57%.加标回收率为86.7%～98.8%.对5种常见的食品包装材料样品进行了测定, 所建立的方法简便、快速、灵敏,适合于食品包装材料中酚类环境激素的检测.