Analysis of metabolic markers of tea origin by UHPLC and high resolution mass spectrometry

Tea is an infusion made from the dried leaves of Camellia sinensis L. and is the second most consumed beverage in the world. It has been shown that factors such as fermentation methods, cultivar, geographical origin and season can affect the biochemical composition of tea. In this study, the biochemical composition of green, oolong and black commercial tea samples from around the world was studied using a non-targeted method utilising reversed phase ultra high pressure liquid chromatography (UHPLC) and high resolution mass spectrometry. Principal component analysis of green, oolong and black tea extracts clearly showed that fermented tea can be resolved from non-fermented tea. When the non-targeted data were combined with the supervised multivariate technique, partial least squares discriminant analysis, the method was able to clearly distinguish ‘country of origin’ within green tea and to a lesser extent within a black tea sample set, plus provide indicative marker ions for the country of origin. Many of the significant components detected in this study are unknowns, emphasising the importance of un-biased non-targeted analytical techniques. This study highlights the potential efficacy of non-targeted UHPLC–mass spectrometry when combined with multivariate statistics to differentiate fermented from non-fermented tea and provide potential indicators of provenance of tea samples for further examination.     

外墙保温材料的种类及防火性能分析

讨论了常见外墙保温材料的主要种类,按照国家有关标准对各种材料进行防火性能实验,对外墙保温材料的防火性能进行分析与讨论。     

基于发动机虚拟实验室的负荷特性实验设计

本文基于在教育、开发设计以及协同实验领域有较广泛的应用的虚拟实验室技术,设计了发动机虚拟教学实验室,采用C#和MATLAB混合编程,通过适当的程序设计将发动机负荷特性实验的操作过程虚拟化。对于教学实验节约了大量的时间和资金,操作提示程序加深学生对实验流程和测定参数的理解,数据处理模块便于学生对于实验曲线图的理解,实验室程序人机交互界面友好、维护简单、有较好的扩展性。     

Battery impedance characterization through inspection of discharge curve and testing with short pulses

A simple method is proposed for battery impedance characterization at low frequencies (relevant to the electrochemical processes) and at higher frequencies (relevant to the double-layer process). The electrochemical impedance at very low frequencies is described using discharge curve information. This method makes it possible to distinguish between outwardly similar batteries that differ in backup times. The double-layer impedance at higher frequencies is characterized using short testing pulses. It is shown that the double-layer impedance of the negative electrode is observable in hertz range while the positive electrode is observable at the boundary to the millihertz range. The double-layer impedance of deeply discharged battery is observable at higher frequencies than the impedance of fully charged (or significantly discharged) battery because the electrodes are less overlapping in frequency and the spectrum shift to the higher frequencies is larger especially for the negative electrode.     

短链醇对CTAB/KCl混合溶液粘度的影响

采用粘度法研究了在KBr存在条件下,乙醇、丙醇以及丁醇对十六烷基三甲基溴化铵(CTAB)水溶液粘度的影响。结果表明,丙醇和丁醇的加入会导致溶液的相对粘度先上升后下降,而乙醇浓度的增加会引起溶液相对粘度的持续下降。在此基础上进一步探讨了不同链长的醇与表面活性剂形成的胶束之间的疏水相互作用及其对表面活性剂聚集形态的影响。     

基于电力载波和物联网技术的建筑节能测评系统

建筑物的能耗检测点众多,针对传统的逐点检测方法效率低下问题,该系统采用电力载波技术将分散的检测值自动传输到各数据采集系统中,再借助3G无线网络远传到物联网节能测评服务平台上,由系统自动计算整体建筑的能耗情况,并给出节能综合评价结果.     

昌化明矾石石英地鸡血石的宝石矿物学特征

利用宝石学常规手段、偏反光显微镜、红外光谱仪、X射线粉末衍射仪和X荧光光谱仪等测试方法对昌化明矾石石英地鸡血石的宝石矿物学特征进行了较详细的分析。结果发现,该品种鸡血石中的"地"主要由明矾石和石英组成,并含少量的黄铁矿和镜铁矿,不含地开石和高岭石。据其透明度、光泽、硬度等特征应归属于"刚地"鸡血石,但其矿物组成明显不同于其它含有粘土矿物的昌化"刚地"鸡血石。X荧光光谱仪的测试结果显示,样品中含有一定量的Sr和Ba,推测其可能含有少量的天青石-重晶石的类质同象系列矿物。     

浓香型白酒窖泥中芽孢杆菌的分离鉴定及代谢产物分析

从浓香型白酒窖泥中筛选出3细菌,经磷脂脂肪酸（PLFA）鉴定,分别为球形赖氨酸芽孢杆菌（Lysinibacillus sphaerieus）、短短芽孢杆菌（Brevibacillus brevis）、尘埃类芽孢杆菌（Paenibacillus larvae subsup. pulvifaciens）。采用固相微萃取结合气相色谱-质谱联用（SPME-GC-MS）技术分析3株菌发酵产物,结果表明,3株菌产风味物质能力较强且种类丰富,主要为高级醇、高级酮等芳香类化合物,它们作为白酒中的微量成分,对浓香型白酒风味的形成起着放香、助香及调香的作用。因此,这3株菌的代谢产物对浓香型白酒风味物质的形成有一定影响。     

超高效液相色谱串联质谱法同时检测13种植物生长激素残留物

目的采用超高效液相色谱-三重四极杆质谱技术,建立促进农作物生长的13种植物生长激素残留的检测方法。方法样品加甲醇超声提取,离心净化后进样分析,分析物经C_(18)色谱柱分离,以甲酸铵-乙腈溶液作为流动相梯度洗脱,在电喷雾正、负离子扫描、多反应监测模式下,外标法定量分析,同时探讨了前处理和仪器分析条件对检测的影响。结果 13种常见植物生长调节剂在1～1000μg/L范围内,峰面积与质量浓度的线性关系良好;当添加浓度水平在50、100、500μg/kg时,13种植物生长调节剂的平均回收率为92.5%～103.5%,相对标准偏差(relative standard deviation,RSD)为1.7%～5.6%,检出限(limit of detection,LOD)为0.8～4.2μg/kg。结论本方法简化了样品前处理步骤,具有良好的可靠性和灵敏度,适于植物源性食品中植物生长激素的快速检验与分析。     

导电聚合物-纤维素纤维复合材料研究新进展

导电聚合物与纤维素纤维的复合可实现功能互补,相应复合材料具有较大利用潜力。本文概述了近年来导电聚合物 纤维素纤维复合材料研究的一些新进展。导电聚合物 纤维素纤维复合材料的制备方法有：原位液相化学聚合法、气相化学聚合法、喷墨打印法、聚电解质吸附法、层层自组装法、吸附胶团聚合法、电化学聚合法等。不同方法各具特色,亦有交叉性与重叠性。其中,原位液相化学聚合法因制备过程简单、成本较低和环境友好而备受关注,已有的研究进展为复合材料在功能纸和水体净化材料等方面的应用奠定了理论基础。在对新进展进行概述的基础上,提出了今后导电聚合物 纤维素纤维复合材料具有发展潜力的研究方向。