茶叶及茶多酚中儿茶素的高效液相色谱分析方法研究

 筛选出HypersilBDSC18和ZorbaxSBC18两种适合同时分离茶叶和茶多酚中 7种儿茶素和咖啡因的反相柱。采用甲醇 水 醋酸 (或三氟醋酸 )作流动相 ,分别以等强度洗脱和梯度洗脱 (均在 30min内 )分离测定了我国 6种不同产地茶叶样品和 3种茶多酚样品中 7种儿茶素的含量。考察了 7种儿茶素和咖啡因的保留值与流动相组成及柱温的关系 ,优化了色谱条件及样品前处理方法。用电喷雾电离质谱 (ESI MS)定性确认没食子儿茶素没食子酸酯(GCG)和儿茶素没食子酸酯 (CG)两组分 ,并用高效液相色谱制备两对照品用于定量分析。     

ISO方法与常规方法测定茶叶中茶多酚总量及儿茶素组分上的差异比较

分别采用ISO方法和常规分析方法(GB/T 8313-2002等)分析了茶叶中茶多酚总量以及儿茶素组分.采用GB/T 8313-2002测定的绿茶、白茶、鸟龙荼和红茶茶样中的茶多酚总量数值分别是采用ISO 14502-1:2005(E)方法的1.43、1.47、1.46和1.72倍;而采用ISO 14502-2:20Q5(E)方法测定的儿茶素总量数值明显高于文中所采用的其它两种分析方法所得的测定数值,采用ISO 14502-1:2005(E)方法测定的绿茶、白茶、乌龙茶和红茶茶样中的儿茶素总量数值分别是采用的方法2#(茶汤提取方法参照GB/T 8313-2002)的1.53、1.46、1.24和1.04倍.该研究为不同文献中采用不同方法测定的茶多酚总量和儿荼素组分之间的比较提供了初步依据.     

茶多酚测定结果与绿茶品质关系的研究

结合茶叶样品中儿茶素含量的检测,研究了两种茶多酚测定方法-酒石酸铁法和Folin-Denis法的多酚检测结果与绿茶品质的关系.结果表明,对于同一绿茶样品,所选用的检测方法不同,多酚检测结果也有所不同.多酚检测结果与绿茶样品中儿茶素的组成、比例有关.     

5种分散吸附剂对茶叶乙腈提取液组分的吸附作用研究

考察了丙基乙二胺(PSA)、C18、石墨化炭黑(GCB)、氧化铝、弗罗里硅土对茶叶乙腈提取液组分(茶多酚、儿茶素类化合物、咖啡碱和叶绿素)的吸附作用。结果表明:C18和GCB显著降低茶叶乙腈提取液颜色深度;PSA对茶多酚和儿茶素类化合物具有较强的吸附作用,50～200 mg PSA使提取液中茶多酚的含量下降了16.3%～67.7%,其它4种吸附剂使提取液中茶多酚的含量下降了0.33%～20.3%。GCB对提取液中的咖啡碱有较好的吸附效果,50～200 mgGCB使提取液中咖啡碱的含量下降了26.4%～68.2%,其它4种吸附剂使提取液中咖啡碱的含量下降了6.32%～28.6%。另外,PSA对叶绿素a和叶绿素b均有较好的吸附效果,且对叶绿素b的吸附效果比叶绿素a明显。     

茶多酚的表面性能研究

通过分别测试二碘甲烷、水、甲酰胺等液体在茶多酚上的接触角,并根据van Oss-Chaudhury-Good的组合理论对茶多酚的表面性能进行研究。结果表明茶多酚的表面能随着茶多酚的含量增加而提高;且随着茶多酚的含量增加,儿茶素类物质即含酚羟基类物质的含量进一步增加,形成氢键的几率进一步增大,导致分子之间作用力和氢键力加大,因而使茶多酚的表面能提高。     

鲁米诺-过氧化氢-铜(Ⅱ)化学发光法测定儿茶素

1　引　　言儿茶素是从茶叶中提取的天然多酚类化合物 ,具有很好的抗氧化、抗自由基活性。常用的测定茶多酚含量的方法有高锰酸钾滴定法、酒石酸亚铁分光光度法、ＨＰＬＣ法等。作者发现儿茶素对鲁米诺 Ｈ2 Ｏ2 Ｃｕ 体系的化学发光有强烈的抑制作用 ,据此建立了一种高灵敏度的儿茶素测定方法。线性范围 7.0× 10 -7～ 1.0× 10 -5ｍｏｌ/Ｌ ;检出限为 5 .0× 10 -7ｍｏｌ/Ｌ ;对 8.6× 10 -6ｍｏｌ/Ｌ的儿茶素连续 9次测定的相对标准偏差为 1.0 %。用该方法测定茶多酚的含量 ,得到满意结果。2　实验部分2 1　仪器与试剂　ＤＲＩ Ｂ化学…     

脉冲辐解研究茶多酚4个组分清除羟自由基机理

采用脉冲电子辐解瞬态吸收光谱法 ,在pH 7的磷酸缓冲水溶液中测定茶多酚 4个组分表没食子儿茶素没食子酸酯 (EGCG)、表儿茶素没食子酸酯 (ECG)、表没食子儿茶素 (EGC)和表儿茶素 (EC)的清除羟自由基速率常数分别为 1 .5× 1 0 10 ,1 .4× 1 0 10 ,9.7× 1 0 9和 9.2× 1 0 9dm3 ·mol-1·s-1,并提出了EGCG和ECG在清除羟自由基的过程中存在一个脱没食子酸基团的机理     

半制备型液相色谱法分离纯化茶叶鲜叶中7种儿茶素类化合物

建立了从茶叶鲜叶中分离纯化7种儿茶素类化合物(没食子儿茶素(GC)、表没食子儿茶素(EGC)、儿茶素(C)、表没食子儿茶素没食子酸酯(EGCG)、表儿茶素(EC)、表没食子儿茶素3-O-(3-O-甲基)没食子酸酯(EGCG3"Me)和表儿茶素没食子酸酯(ECG))的半制备色谱法。铁观音鲜叶经甲醇超声浸提、浓缩、氯仿萃取后,向水相中加入碱式醋酸铅沉淀,得到茶多酚粗品。分别以甲醇-水、乙腈-水作为流动相,采用半制备色谱法纯化7种儿茶素类化合物,纯度均达到90%。此外,利用同样的方法分离纯化另外两种茶叶鲜叶中的7种儿茶素类化合物,得到相似的结果。该方法以溶剂提取、离子沉淀结合半制备色谱,适于简单、高效地同时分离制备多种儿茶素类化合物。     

近红外光谱在无机微量成分分析中的应用

由于近红外光谱的独特优势, 在实际复杂样品分析中发挥了重要作用. 但由于近红外光谱的信号相对较弱, 无机离子在近红外光谱中一般没有响应, 因此难以用于微量成分特别是无机微量组分的测定. 总结了近红外光谱技术在环境、土壤、植物及生物样品分析中的应用, 说明了近红外光谱用于无机微量成分分析的原理. 由于近红外光谱技术一般通过多元校正方法进行定性定量分析, 利用组分间的相互作用或组分含量之间的相关性可以实现微量组分或无光谱响应组分的定量分析. 还总结了富集技术在近红外光谱分析中的应用, 利用富集技术可实现稀溶液中金属离子含量的快速测定, 并可以改善分析的灵敏度和检测限.     

CCD近红外光谱快速测定喷气燃料的冰点

从化学计量学角度研究了近红外光谱技术测定航空燃料冰点的原理．使用偏最小二乘法分别建立了短波近红外和长波近红外的航空燃料冰点快速测定模型．将近红外法冰点测定结果和标准方法（ＧＢ ２４３０—８１）测定结果进行了比较，两种结果吻合得很好（标准偏差为１．４７℃。），近红外光谱法具有分析精度高（标准偏差为０．５３℃），快速（单个样品分析时间为 ｌｍｉｎ）和操作方便的优点．实际分析结果表明，石油化工科学研究院研制的ＣＣＤ短波近红外光谱仪分析性能达到进口傅立叶近红外光谱仪水平。     

Microwave‐assisted extraction followed by CE for determination of catechin and epicatechin in green tea

In this work, for the first time, microwave‐assisted extraction (MAE) followed by CE was developed for the fast analysis of catechin and epicatechin in green tea. In the proposed method, catechin and epicatechin in green tea samples were rapidly extracted by MAE technique, and then analyzed by CE. The MAE conditions and the method's validation were studied. It is found that the extraction time of 1 min with 400 W microwave irradiation is enough to completely extract catechin and epicatechin in green tea sample, whereas the conventional ultrasonic extraction (USE) technique needs long extraction time of 60 min. The method validations were also studied in this work. The calibration curve shows good linearity in 0.01–3 mg/mL for catechin (R²=0.993), and 0.005–3 mg/mL for epicatechin (R²=0.996), respectively. The RSD values for catechin and epicatechin are 0.65 and 2.58%, respectively. This shows that the proposed method has good reproducibility. The proposed method has good recoveries, which are 118% for catechin and 120% for epicatechin. The proposed method was successfully applied to determination of the catechin and epicatechin in different green tea samples. The experiment results have demonstrated that the MAE following CE is a simple, fast and reliable method for the determination of catechin and epicatechin in green tea.     

Rapid, direct determination of polyphenols in tea by reversed-phase column liquid chromatography.

Column liquid chromatography on a C18-bonded silica column with water-methanol-acetic acid as eluent was used to determine polyphenols and caffeine in tea. Without any pretreatment, catechin, epicatechin gallate, epigallocatechin gallate, epigallocatechin, epicatechin and caffeine were separated successfully within 15 min. The detection limits (S/N = 3) of polyphenols studied were 1.8-24 mg/l at a detection wavelength 270 nm. The linear range of the peak area calibration curves for the analytes were over two orders of magnitude with a correlation coefficient of 0.996-0.999. Using this method, some Chinese tea samples were analyzed with a good reproducibility (RSD are below 5%).     

Voltammetric evaluation of the antioxidant capacity of tea on electrodes modified with multi-walled carbon nanotubes

The characteristics of the voltammograms of tea polyphenols on a glassy carbon electrode modified with multi-walled carbon nanotubes (MCNT-GCE) were evaluated. With the use of atomic force microscopy, it was found that MCNTs are oriented as rows 0.8–1.0 μm wide with alternating hills to 586 nm in height. Polyphenols other than of tannin are reversibly oxidized at the first step. Corresponding electrode reaction schemes are proposed. A voltammetric procedure for the estimation of the antioxidant capacity (AOC) of tea based on the oxidation of its polyphenol compounds was developed. The voltammograms of tea exhibited clearly defined peaks and oxidation steps whose potentials depend on the type of tea. The area of oxidation peaks was chosen as the parameter that characterizes antioxidant properties. The AOC of tea was expressed in terms of catechin equivalents per 100 mL of a beverage. 27 tea samples were analyzed. It was found that the AOC of green tea is 79% higher than that of black tea (290 ± 40 and 54 ± 22 mg/100 mL, respectively, P < 0.05). The AOC of oolong tea (70 ± 5 mg/100 mL) is considerably lower than that of green tea and statistically insignificantly higher than that of black tea. The AOC of white tea is comparable with the AOC of green tea (255 ± 11 and 290 ± 40 mg/100 mL, respectively, P > 0.05).     

Folin-Ciocalteu分光光度法测定茶多酚锌配合物中多酚的含量

以没食子酸为对照品,采用Folin-Ciocalteu比色法测定了茶多酚锌配合物(TP-Zn)中多酚的含量.结果表明,多酚质量浓度在0～8.54 mg ·L-1范围内与吸光度呈良好的线性关系;稳定性、精密度、重现性和回收率实验的相对标准偏差在0.39％～1.23％范围内.该法是一种简便、快速、准确测定茶叶制品中多酚含量...     

Effect of Water Hardness on Catechin and Caffeine Content in Green Tea Infusions

The health benefits of green tea are associated with its high catechin content. In scientific studies, green tea is often prepared with deionized water. However, casual consumers will simply use their local tap water, which differs in alkalinity and mineral content depending on the region. To assess the effect of water hardness on catechin and caffeine content, green tea infusions were prepared with synthetic freshwater in five different hardness levels, a sodium bicarbonate solution, a mineral salt solution, and deionized water. HPLC analysis was performed with a superficially porous pentafluorophenyl column. As water hardness increased, total catechin yield decreased. This was mostly due to the autoxidation of epigallocatechin (EGC) and epigallocatechin gallate (EGCG). Epicatechin (EC), epicatechin gallate (ECG), and caffeine showed greater chemical stability. Autoxidation was promoted by alkaline conditions and resulted in the browning of the green tea infusions. High levels of alkaline sodium bicarbonate found in hard water can render some tap waters unsuitable for green tea preparation.     

UF-两段厌氧处理茶多酚废水的研究

采用前置超滤膜(UF)的两相厌氧工艺对原水COD为18362.6mg/L,荼多酚为3608.3mg/L、色度为2624.2倍的茶多酚生产废水进行为期90d的实验研究.结果表明,当实验压力为0.2Mpa时,膜组件对COD去除率为63.4%,茶多酚去除率为95.1%,色度去除率为93.4%.然后,对两相厌氧工艺的投配率、P含量和酸化段水力停留时间(HRT1)对废水COD、色度与茶多酚去除率和产气率的影响进行了研究.当投配率为15.0%、P含量为38.1mg/L、HRT1=24h,该工艺达到最佳处理效果,出水COD为1288.1mg/L,COD去除率为80.8%,色度为95.6倍,色度去除率为44.6%,残余茶多酚为119.8mg/L,茶多酚去除率为32.3%,产气率为0.85m3/kg COD,与未采用UF预处理的两相厌氧水解工艺相比,COD、色度和荼多酚去除率分别提高23.40%,10.2%和1613%,产气率增加0.15m3/kg COD.     

Extraction of Catechin Compounds from Green Tea with a New Green Solvent

An emerging green solvent called a deep eutectic solvent（DES） was applied to the extraction and determination of catechin（C）,（＋）epicatechin gailate（ECG） and （-）epigallocatechin gallate（EGCG） from Chinese green tea.After evaluating different combinations of them by extraction methods and DESs,a DES-based extraction method was established and optimized by a systematic investigation of the influencing factors.As a result,a total of 3.629,35.25 or 114.2 mg/g catechin,（＋）epicatechin gallate or （-）epigaliocatechin gallate were extracted respectively under optimal conditions with extraction efficiencies of 82.7％,92.3％ and 97.0％,respectively.By comparing with other common used solvents for extracting catechin compounds,DESs were proved to be potential extraction solvents for bioactive ingredients.     

等度反相高效液相色谱法测定茶多酚中的儿茶素和咖啡因

 介绍一种简便的等度反相高效液相色谱分析茶多酚中 5种儿茶素和咖啡因的快速方法。样品总的分析时间在 0 5h内。色谱柱为ResolveC18;流动相为水 体积分数为 85 %的磷酸水溶液 乙腈 N ,N 二甲基甲酰胺 (DMF)(体积比为 85 9∶1∶12 0∶2 0 ) ;柱温为 43℃ ;紫外检测波长为 2 80nm。研究了流动相中改良剂DMF与容量因子的关系。被测组分的含量与其峰面积有良好的线性关系 (r =0 .9992～ 0 .9999) ;加标回收率在 83.33%～ 10 4.42 %(RSD在 0 .74%～ 1.43% )。     

High throughput qualitative analysis of polyphenols in tea samples by ultra-high pressure liquid chromatography coupled to UV and mass spectrometry detectors

The analysis of polyphenols in tea extracts is important due to their potential health benefits. Therefore, efficient and high throughput analytical methods have been developed for the separation of seven predominant polyphenols, also known as catechin derivatives, present in tea extracts. Columns packed with sub-2-μm particles operating at elevated pressure (UHPLC strategy) were selected to improve chromatographic performance. The potential of UHPLC–UV was demonstrated with baseline resolution of all standard catechins in only 30 s using a 50-mm column packed with 1.7-μm particles. When dealing with real samples such as tea extracts, however, longer columns of up to 150 mm in length were employed to enhance the separation of catechin derivatives and other constituents within the tea samples while maintaining an acceptable analysis time. Two strategies based on 2-D experiments were proposed to clearly identify catechins. Firstly, a liquid–liquid extraction procedure was added prior to the UHPLC–UV analysis to decrease the complexity of the sample. Secondly, UHPLC was coupled to ESI-MS/MS to attain sufficient sensitivity and selectivity between catechin derivatives and other constituents of tea extract. These two strategies were found extremely promising as a clear discrimination of catechins from the matrix could be attained.