反相高效液相色谱法测定可乐、茶叶中的咖啡因

研究了反相高效液相色谱法（RP－HPLC）直接测定茶叶水提取物、可乐饮料中的咖啡因的新方法，采用PE－C18柱，以CH3OH－H2O－HAc(30:69.92:0.08)溶液作流动相，紫外检测波长为260nm。可在8min内将咖啡因与基体分离，咖啡因含量与峰面积在10μg/mL－100μg/mL范围呈线性关系，回归方程为：Y＝33567c(μg/mL)-126421,r=0.9997.该法可用于可乐饮料，茶叶产品质量的监控及产品真伪的辨别。     

用荧光探针法研究茶叶花粉黄酮对氧自由基致鼠红细胞膜氧化损伤的保护作用

应用1,6-二苯基-1,3,5-已三烯(DPH)为荧光探针,超氧阴离子自由基和羟基自由基致鼠红细胞膜氧化损伤为模型,研究了茶叶花粉黄酮对鼠红细胞膜氧化损伤的影响.结果表明,超氧阴离子自由基和羟基自由基均能引起鼠红细胞膜脂质过氧化反应,脂质过氧化产物丙二醛含量显著升高,膜脂流动性下降.将鼠红细胞膜预先用茶叶花粉黄酮处理后,膜脂的MDA含量明显下降,呈现剂量与效应关系,膜脂流动性显著提高,表明茶叶花粉黄酮对超氧阴离子自由基和羟基自由基引起的鼠红细胞膜的氧化损伤有保护作用.     

UE/ME-GC-MS提取分析普洱茶的挥发和半挥发性成分

采用超声波提取（UE）和微波萃取（ME）两种前处理方法提取普洱茶的挥发性成分,利用气相色谱-质谱（GC-MS）联用仪进行定性检测,并加入乙酸苯乙酯作为内标进行定量分析。结果表明：两种萃取方法共鉴定出挥发性成分88种,其中超声波萃取检测出79种,微波萃取检测出69种。普洱茶的主要挥发性成分有11,14,17-二十三碳烯酸甲酯、咖啡因、棕榈酸、维生素E、β-香树脂醇、植醇等。超声波萃取法得到的提取率较高,而微波提取法耗时较短,两者各有所长,应根据需要来选择。     

固相微萃取/加速溶剂萃取-气相色谱-质谱法分析青山绿水茶叶的挥发性成分

采用固相微萃取(SPME)和加速溶剂萃取(ASE)两种前处理方法从青山绿水茶叶(也叫苦丁茶)中提取挥发性成分,用气相色谱-质谱法(GC-MS)定性。实验结果表明:两种前处理方法共检测出91种成分,SPME检出49种,ASE检出56种,共同组分14种。青山绿水茶叶的挥发性成分主要成分有β-月桂烯、3,3,5-三甲基-1,5-庚二烯、L-柠檬烯、α-罗勒烯、β-罗勒烯、β-蒎烯、2-甲基安息香醛和5-羟甲基糠醛等物质。这两种提取方法各具优势,共同应用可以起到取长补短的作用。     

改进的氧瓶燃烧法结合电感耦合等离子体质谱快速测定茶叶样品中的稀土元素含量

建立了电感耦合等离子体质谱法快速测定茶叶中Y~Lu共15种稀土元素的新方法,样品处理基于改进的氧瓶燃烧法,以涂覆甘油的石英布代替滤纸作为引燃和燃烧载体,在500 mL容积燃烧瓶中实现了0.1 g样品量的有氧完全燃烧。系统优化了样品处理关键参数,以5 mL 4％ HNO3+1％ HF(V/V)组合试剂超声提取燃烧残渣1 min,稀土元素回收率大于90％,样品总处理周期小于3 min。6次样品平行测定值的相对标准偏差(RSD)在2.7％~5.5％之间,方法检出限(3σ)在0.001~0.006 mg/kg之间。采用本方法对3种茶叶标准参考物质进行分析,测定结果和标准值吻合良好。     

Magnetically separable tea leaf mediated nickel oxide nanoparticles for excellent photocatalytic activity

Synthesis of nanoparticles having low chemical toxicity has been interest of researchers for decades. Utilization of plant phytochemicals as reducing agent is now a globally recognized alternative technique for environmental friendly and low-cost production of nanoparticles. This work reports a facile green synthesis protocol of Nickel Oxide nanoparticles (NiO NPs) using fresh tea leaf extract. The synthesized nanoparticles have been characterized through various analytical techniques like Powder XRD (P-XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The XRD results reveal the formation of crystalline nickel oxide nanoparticles. FTIR spectrum displays the existence of different polyphenolic groups over NiO NPs surface. TEM and SEM images indicate the formation of slightly agglomerated spherical nanoparticles with particle size 3–5 ​nm. The nanoparticles were used towards the photocatalytic degradation of both cationic, anionic dyes and their mixtures under optimum conditions in the presence of UV light irradiation. More than 95% degradation was observed for all the dye solutions with 30 ​mg ​L^-1 catalytic dose. Moreover, the degradation efficiency of the nanoparticle was studied by altering various parameters like pH, initial dye concentration and amount of catalytic dose. Pseudo first order kinetic model was employed in all the reactions. A detailed mechanism and kinetics of the all the reactions were studied. Interestingly, the catalyst showed excellent recyclability up-to 4th cycles with very low catalytic activity loss.     

Separation and purification of both tea seed polysaccharide and saponin from camellia cake extract using macroporous resin

A novel method to separate and purify tea seed polysaccharide and tea seed saponin from camellia cake extract by macroporous resin was developed. Among four kinds of resins (AB‐8, NKA‐9, XDA‐6, and D4020) tested, AB‐8 macroporous resin possessed optimal separating capacity for the two substances and thus was selected for the separation, in which deionized water was used to elute tea seed polysaccharide, 0.25% NaOH solution to remove the undesired pigments, and 90% ethanol to elute tea seed saponin. Further dynamic adsorption/desorption experiments on AB‐8 resin‐based column chromatography were conducted to obtain the optimal parameters. Under optimal dynamic adsorption and desorption conditions, 18.7 and 11.8% yield of tea seed polysaccharide and tea seed saponin were obtained with purities of 89.2 and 96.0%, respectively. The developed method provides a potential approach for the large‐scale production of tea seed polysaccharide and tea seed saponin from camellia cake.     

热解吸-电喷雾离子源-三重四极杆质谱法快速筛查火锅底料和肉汤中非法添加罂粟壳

通过简单的金属探针直接接触火锅底料和肉汤表面采集待测物,经热解吸离子源进一步热解吸和电喷雾离子化,最终进入三重四极杆质谱检测器在多反应监测模式下进行定性分析,实现了火锅底料和肉汤中罂粟壳的现场实时快速检测。结果表明,设置热解吸温度为260℃,以0.1%甲酸水溶液（含10 mmol/L甲酸铵-乙腈（1:1,v/v）作为注射溶剂、注射泵流速为200 μL/h时,仪器响应值最优,灵敏度最高;5种生物碱中罂粟碱、那可丁、蒂巴因在火锅底料和肉汤中的检出限均为2 μg/kg,可待因、吗啡在火锅底料中的检出限为10 μg/kg,在肉汤中的检出限为5 μg/kg。该法与罂粟壳胶体金卡片快检试剂盒相比,灵敏度具有明显优势。应用该法对50批次市售火锅底料、肉汤等样品进行检测,发现1批次鸡汤含有那可丁、罂粟碱、蒂巴因和吗啡4种生物碱,与高效液相色谱-三重四极杆质谱法的检测结果一致。由此说明该方法具有无需样品制备和色谱分离的特点,是一种快速、绿色、环保的分析方法,能够满足对食品中罂粟壳的快速定性分析。     

ICP-OES测定奶茶粉中的常量、微量元素

采用干法灰化法处理奶茶粉样品,建立电感耦合等离子体发射光谱法(ICP-OES)同时测定奶茶粉中常量、微量元素的方法.该方法以钪作为内标以补偿仪器波动,采用不同标准系列分组以消除光谱干扰.方法检出限为0.02-8.77μg/g,相对标准偏差均小于3%,回收率为93.9%-109.4%.方法操作简单、分析速度快、灵敏度高、...     

ICP-AES测定青岛崂山绿茶中的微量元素

采用HNO3-H2O2混合酸,密闭微波消解样品,应用ICP-AES测定青岛崂山绿茶中Al、Ca、Cd、Co、Cr、Cu、Fe、K、Mg、Mn、Na、Ni、Pb、Se、Sr、V和Zn等17种营养元素及重金属元素的含量。测定结果的相对标准偏差均小于3.50%,对17种元素的加标回收率在90.0%—110.2%之间,采用该方法测得的茶叶标准物质（GBW10016）的17种元素的值均在标准值范围内,方法准确度高。实验结果表明青岛崂山绿茶中含有大量对人体有益的元素包括Ca、Co、Cr、Cu、Fe、K、Mg、Mn、Na、Ni、Se、Sr、V和Zn等,另外也检测到含有Al,Cd和Pb等有毒、有害元素,但是含量很低,对人体的不利影响可以忽略不计。