SPE and HPLC/UV of resin acids in colophonium-containing products

A new method, involving SPE and HPLC/UV diode-array detection (DAD), was developed for the quantification of colophonium components in different consumer products, such as cosmetics. Colophonium is a common cause of contact dermatitis since its components can oxidize into allergens on exposure to air. Three different resin acids were used as markers for native and oxidized colophonium, abietic acid (AbA), dehydroabietic acid (DeA), and 7-oxodehydroabietic acid (7-O-DeA). The SPE method, utilizing a mixed-mode hydrophobic and anion exchange retention mechanism, was shown to yield very clean extracts. The use of a urea-embedded C(12) HPLC stationary phase improved the separation of the resin acids compared to common C(18). Concentrations higher than 2 mg/g of both AbA and DeA were detected in wax strips. In this product also 7-O-DeA, a marker for oxidized colophonium, was detected at a level of 28 microg/g. The LODs were in the range of 7-19 microg/g and the LOQs 22-56 microg/g. The method is simple to use and can be applied on many types of technical products, not only cosmetics. For the first time, a method for technical products was developed, which separates AbA from pimaric acid.     

Melt flow behavior of polypropylene composites filled with multi-walled carbon nanotubes during extrusion

Polypropylene (PP) composites filled with multi-walled carbon nanotubes (MWCNTs) were prepared using a twin-screw extruder. The melt flow properties of the composites were measured with a capillary rheometer in a temperature range from 180 to 230 °C and at various apparent shear rates varying from 100 to 4000 s⁻¹. The results showed that the melt shear stress increased almost linearly while the melt shear viscosity decreased almost linearly with increasing shear rates in a bi-logarithmic coordinate system. The melt shear flow followed the power law relationship and the dependence of the melt shear viscosity on temperature obeyed the Arrhenius equation. The relationship between the melt shear viscosity and the MWCNT weight fraction was roughly linear under the investigated range of temperature or shear rate.     

Effect of Layering Pattern on the Mechanical Properties of Bark Cloth (Ficus natalensis) Epoxy Composites

The quest for sustainable materials as a consequence of a global drive to mitigate climate change has led to a focus on natural fiber–reinforced composite materials. In this study, skillful ply angle arrangement of bark cloth–reinforced laminar epoxy composites was carried out for the first time using vacuum-assisted resin transfer molding, and the composites fabricated were characterized for the effect of the layering pattern on their static and dynamic mechanical properties. Tensile strength and flexural strength were shown to be dependent on the ply angle arrangement. Dynamic mechanical analysis of the composites showed a glass transition temperature of 70°C, and the storage modulus and mechanical damping properties showed that the developed composites can withstand considerable loads and have excellent fiber-to-matrix adhesion.     

ICP-AES用于金莲花的无机元素初级形态分析及其溶出特征性研究

采用传统花茶饮用方法对金莲花茶中的Fe、Mg、Cu、Zn、Mn、Cr、Pb、As 8种元素进行浸取;按照初级形态分析流程制备样品溶液,用0.45μm微孔滤膜分离浸取液中的可溶态和悬浮态。应用电感耦合等离子体-原子发射光谱法（ICP-AES）对此花茶中8种无机元素的初级形态进行测定。结果显示：金莲花茶中8种元素的浸出率在17.2%—72.3%之间,可溶态在水浸液中的比率在67.4%—98.6%之间。     

FAAS测定高山绿茶中金属元素含量及溶出性

湿法消解处理和去离子水浸泡后处理高山绿茶样品,采用FAAS测定Fe、Mn、Cu、Zn、Ni等金属元素的含量。金属元素含量为：Mn〉Fe〉Zn〉Cu〉Ni;各元素的加标回收率为95.32%—101.63%;相对标准偏差为1.67%—3.83%,准确度和精密度符合要求;不同浸泡时间茶水中金属元素含量不同,30min浸泡液含量较高,且第一次浸泡液中金属元素含量最高。因此,FAAS测定高山绿茶中金属元素含量及溶出特性的方法可行,实验结果可靠。     

A New Approach to Extracting Roots in Garside Groups

We study the problem of extracting roots in Garside groups by reducing it to the calculation of certain ultra summit sets. Several properties concerning the roots and an effective algorithm are derived. In particular, in the case of braid groups, a conjecture on the bound of super summit set implies that, for fixed number of strands and ordinal number of root, the algorithm is polynomial in the word length.     

固相萃取富集-火焰原子吸收光谱法测定钯

制备了附载有五硫代-15-冠-5(PT15C5)的反相微孔树脂固相萃取柱,并研究了其对钯的固相萃取,含钯样品以0.1mol/L的盐酸介质过柱,样品溶液中的钯可定量吸附在小柱上,富集完后用0.5mol/L的硫脲洗脱小柱上富集的钯,可实现钯的高倍数富集和干扰离子的分离。洗脱液中的钯可用火焰原子吸收光谱法测定,钯浓度在0.1—3.0μg/mL内与吸光度成良好的线性关系;方法用于环境水样中钯的实际测定,相对标准偏差在3.2%—4.1%之间,加标回收率在87.8%—104.7%之间,结果令人满意。     

离子交换富集-ICP-OES测定沉积物中痕量钼

建立了以717型强碱性阴离子树脂富集-电感耦合等离子体-发射光谱法测定沉积物样品中痕量钼的分析方法,优化了各项仪器条件、化学条件及操作参数。并考察了共存离子的干扰。本法测定钼的检出限为0.09μg/L,回收率在98.2%—105.9%之间,方法应用于沉积物样品中微量钼的测定,获得满意的结果。     

化学光谱法测定三氧化二钆中微量钍

采用717阴离子交换树脂分离钍与钆及其他元素,超声波雾化,高频电感耦合等离子体原子发射光谱法测定分离液中微量钍。取样1.0g时,测定下限为0.20μg·g-1,方法回收率为99.2%,相对标准偏差RSD为11.7%(n=6)。     

热塑性酚醛树脂覆膜砂的研究进展

综述了生产热塑性酚醛树脂覆膜砂的原材料 ,混砂工艺 ,再生砂和理论进展等 ,并提出今后覆膜砂的发展方向。