二安替比林（3,4—二甲氧基）苯基甲烷光度法测定茶叶中锰

在碱性介质中，加热时空气氧化Ｍｎ为Ｍｎ，Ｍｎ与二安替比林苯基甲烷反应生成橙色产物，吐温２０和乳酸起到协同增敏作用，λｍａｘ＝４６０ｎｍ，ε＝７．８×１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１，锰量在０－１２μｇ／２５ｍｌ范围内符合比尔定律。     

Spectroscopy Investigation on Conformational Transition of Tea Glycoconjugate from Green Tea

The conformational transition of a new glycoconjugate, tea glycoconjugate (TGC), was investigated by spectroscopy techniques including circular dichroism (CD) and ultraviolet (UV) spectroscopy. The solution behaviors of TGC in the mediums of different temperature, pH value, and ions were compared. Results showed that the native conformation of TGC was partially ordered. The CD value and UV absorbance of TGC altered with the change of pH value, temperature, the addition of ions, and also accompanied order-disorder transition. Especially the conditions with temperature higher than the glass transition temperature (Tg=62℃), higher pH value or lower pH value will have the most impact on the conformation of TGC, which will destroy the hydrogen bonds between the TGC molecules. The results indicated that the outside factors play important roles on the stability of the conformation of TGC.     

茶叶中总黄酮含量测定方法的研究

茶叶中富含羟基苯甲酸类、肉桂酸类及原花色素等多酚类物质,这些物质都具有邻苯二羟基结构,碱性环境下与铝离子形成络合物,影响总黄酮的测定。本实验用亚硝酸钠-硝酸铝法和三氯化铝法测定茶叶总黄酮含量的结果作了比较。实验结果表明,亚硝酸钠-硝酸铝法的测定结果比三氯化铝法约高60mg/g,三氯化铝法在酸性环境下进行,酸度实验显示,适宜酸度为pH≥5.0。鞣酸干扰实验表明,平均误差为0.017mg,随着鞣酸量的增加,测得值无上升趋势。三氯化铝法的线性方程:y=0.000638 0.8623x,相关系数:r=0.9998;样品加标回收率为98.05%。因此,对含酚类较多的植物应采用三氯化铝法测定其总黄酮的含量。     

气相色谱-质谱法测定茶叶中的噻嗪酮残留量

建立了气相色谱-质谱法测定茶叶中噻嗪酮残留量的方法。茶叶中残留的噻嗪酮用丙酮-正己烷混合溶剂(1∶1)提取,提取液经Envi-Carb活性碳柱和LC-Alumina N中性氧化铝柱净化,浓缩定容后,直接用气相色谱-质谱进行分析和确证,外标法定量。以HP-5MS(30m×0.25mm i. d., 0.25 μm)石英毛细管柱为分离柱,噻嗪酮的分离效果良好。方法的线性范围为0.01～1.00μg/mL,检出限为0.01mg/kg,回收率为81.6％～97.2％,相对标准偏差为3.36％～5.78％。质谱监测离子选m/z为105、140、172、305amu,其强度比约为41∶13∶29∶17。样品前处理采用微量化学技术。     

超高效液相色谱-串联质谱法测定茶叶中游离氨基酸成分

建立了使用超高效液相色谱-串联质谱（UHPLC-MS/MS）高效、快速直接测定茶叶中游离氨基酸的方法。通过对质谱、色谱条件及氨基酸提取条件的优化，以含0.2%（体积分数）甲酸的5 mmol/L乙酸铵水溶液和甲醇为流动相进行梯度洗脱，在电喷雾离子（ESI）源正离子扫描模式下检测，通过UHPLC-MS/MS测定，共解析了茶叶中的20种氨基酸。结果表明，茶氨酸（Thea）、Arg、Asn和Asp在50~500 μg/L范围内线性关系良好，其他氨基酸在10~250 μg/L范围内线性关系良好，相关系数均大于0.99；加标回收率为92.3%~109.2%，相对标准偏差为2.00%~9.88%，检出限为0.001~0.011 mg/L，定量限为0.010~0.053 mg/L。该方法灵敏、准确，具有良好的重复性和稳定性，可有效检测出茶叶中的20种氨基酸及氨基类成分。     

气相色谱-负化学源质谱联用法测定菊酯类农药

通过固相萃取-气相色谱-负化学离子源质谱技术建立了11种拟除虫菊酯类农药残留的检测方法，并应用于茶叶农残检测。样品经乙酸乙酯提取后，用串联的活性炭和中性氧化铝固相萃取柱选择性地富集茶叶中待测组分，再由气相色谱-负化学离子源质谱分时段选择离子监测技术进行测定。方法简单快速，一次进样就能得到11种菊酯残留结果；准确度和精密度高，在0．016μg／kg、0．032μg／kg和0．064μg／kg3个添加水平下的回收率在70％～110％之间，CV≤7．4％；选择性好，消除了色素和其它杂质干扰；灵敏度高，检出限低，除了氯菊酯为10μg／kg外，其它菊酯检出限都在μg/∥kg级，七氟菊酯则达到了0．02μg／kg。     

高效液相钴离子催化化学发光抑制法测定茶叶中的茶氨酸

 研究了用高效液相分离、抑制化学发光测定茶叶中茶氨酸的分析方法。该法采用YWG C18(10μm,250mm×5 0mmi d )柱,以0 01mol·L-1醋酸钠 醋酸缓冲液(pH5 5)为流动相,流速为0 8mL·min-1。对茶氨酸抑制Co2+催化鲁米诺(luminol)与过氧化氢(H2O2)化学发光反应的条件进行了优化:Co2+的质量浓度为2μg·L-1,鲁米诺浓度为0 25mmol·L-1,H2O2浓度为0 5mmol·L-1。在茶氨酸的质量浓度为0 2g·L-1～5 0g·L-1时,茶氨酸抑制化学发光产生负峰的相对峰面积Y(将实际峰面积缩小至万分之一)与其质量浓度X(kg·L-1)的线性回归方程为Y=33862X+1 0605(r=0 9983)。     

Feasibility study for the use of near infrared spectroscopy in the qualitative and quantitative analysis of green tea, Camellia sinensis (L.)

This paper indicates the possibility to use near infrared spectroscopy (NIR) combined with PLS as a rapid method to estimate the quality of green tea. NIR is used to build calibration models to predict the content of caffeine, epigallocatechin gallate (EGCG) and epicatechin (EC) and for the prediction of the total antioxidant capacity of green tea. For the determination of the total antioxidant capacity, the trolox equivalent antioxidant capacity (TEAC) method is used. Until now, the prediction of the antioxidant capacity as such by use of NIR has not been reported. For caffeine and TEAC, models are build for the whole green tea leaves and also for the ground leaves. For the polyphenols (EGCG and EC), only models for the whole leaves are investigated. A partial least squares (PLS) algorithm is used to perform the calibration. To decide upon the number of PLS factors included in the PLS model, the model with the lowest root mean square error of cross-validation (RMSECV) for the training set is chosen. The correlation coefficient (r) between the predicted and the reference results for the test set is used as an evaluation parameter for the models: for the TEAC results r=0.90 for the model with the whole leaves, r=0.86 for the model with the powdered leaves are obtained. The caffeine prediction model has a correlation coefficient r=0.96 for the whole leaves and r=0.93 for the ground leaves. The correlation coefficient for the EGCG and the EC content models are, respectively 0.83 and 0.44.     

微波衍生-离子对高效液相-磺化四苯基卟啉光度法同时测定痕量镍、铜、锰和锌

 用磺化四苯基卟啉 (TPPS4 )作柱前衍生试剂 ,在微波作用下进行衍生反应 ,研究了衍生和分离Ni2 + ,Mn2 + ,Zn2 + 和Cu2 + 的最佳条件。在 75 0W的微波作用下衍生反应 3min ,在C18柱上采用乙腈 水 (体积比为 2 2 5∶77 5 )体系作流动相 ,四乙基溴化铵 (TEABr)作离子对试剂 ,在 415nm处检测 ,建立了微波衍生 离子对高效液相快速分离、光度检测Ni2 + ,Mn2 + ,Zn2 + 和Cu2 + 的新方法。络合物和反应试剂在 15min内出峰完毕。Zn2 + ,Cu2 + ,Ni2 + 和Mn2 + 的检测限分别为 0 0 5 μg/L ,0 0 1μg/L ,0 10 μg/L和 0 40 μg/L。     

单柱离子色谱法测定茶叶中草酸根和硫酸根的研究

本文研究单柱离子色谱分离测定茶叶中微量草酸根和硫酸根的方法。样品水浸泡，酸化液。上ＳｈｉｍＰａｒｓｋＩＣ－Ａ＿２柱分离，用２．０ｍｍｏｌ·Ｌ￣（－１）Ｈ－２Ｃ＿８Ｏ＿４／１．９ｍｍｏｌ·Ｌ￣（－１）Ｔｒｉ淋洗液洗脱，电导检测器检测，检测灵敏度为１．６Ｓ／ｃｍ，最低检出限０．０５μｇ／ｍＬ；线性范围Ｌ；相对标准偏差１．０６％；平均回收车９８．７２％９７．８８／。该法简便、快速、准确、灵敏、选择性好。