Rapid analysis of flavonoids based on spectral library development in positive ionization mode using LC-HR-ESI-MS/MS

Natural product screening in plants has always been a difficult task due to the complex nature of the plant material and diverse structures of the compounds present in them. Flavonoids are important and diverse class of plant secondary metabolites with numerous medicinal activities. The present study focuses on the development of a high-resolution tandem mass spectral library for the rapid and authentic identification of common flavonoids. A total of forty flavonoid standards belong to class flavones, isoflavones, flavanones, flavanols and anthocyanins were pooled into two solutions applying logP-based strategy. The flavonoids were analyzed using LC-QTOF-MS high-resolution mass spectrometer with optimization of different instrumental parameters to achieve good sensitivity. The library was built by incorporating names, molecular formulae, exact masses, and MS, and MS/MS spectra of analyzed flavonoids using Bruker Library Editor tool. The fragmentation pattern observed for the standard compounds were compared to the fragments reported in the literature. To assess the practical implications, an extract of tea sample was analyzed and screened using the developed library, which resulted in the identification of three common flavonoids based on their HR-ESI-MS/MS spectral features. The established LC-HR-MS/MS method can be used for the targeted identification of flavonoids in complex samples like food material from different botanical families.     

茶叶中的铅

采用原子吸收汾光光度法对我国一些常用茶中Ｐｂ进行了测定，结果表明茶叶中的Ｐｂ通过一般食品，应引起重视。     

茶叶香味扫描和挥发性化学成分分析

为区分不同茶叶的香味，利用电子扫描仪对铁观音、兰贵人、玉针、碧螺春和云雾茶等5种茶叶进行了香味扫描，确定了电子鼻在茶叶香味辨别中的作用。采用固相微萃取．气相色谱／质谱联用法对这5种茶叶样品中的挥发性化学成分进行了定性和定量分析，分别鉴定出40、40、35、16和13种化合物。在鉴定出的化学成分中，乙酸、大茴香醚、十六烷、咖啡因、十六酸和双酚A是5种茶叶样品中所共有的化学成分，每种茶叶样品中又都含有一些特有的化学成分。最后对香味扫描结果和挥发性化学成分分析结果进行了分析，研究了挥发性化学成分组成和含量上的差别，对茶叶样品数据点在香味分析三维图中位置的影响。     

二溴对甲偶氮羧用于茶叶中微量钡的研究

通过对钡与新试剂二溴对甲偶氮羧的显色反应的研究,建立了一种测定茶叶中微量钡的光度分析方法。在0.2mol·L-1磷酸溶液中,钡与二溴对甲偶氮羧发生灵敏的显色反应,生成一个1∶2的配合物。钡(Ⅱ) 二溴对甲偶氮羧配合物的最大吸收峰位于609nm,摩尔吸光系数和Sandell灵敏度分别为3.26×104L·mol-1·cm-1和0.0042μg·cm-2;在25ml溶液中,0～40 0μg钡(Ⅱ)符合比耳定律;当采用氟化钠和草酸作掩蔽剂时,绝大多数金属离子不干扰钡的测定,尤其是对钙和锶有较大的允许量,方法的选择性好于目前所用的其它钡试剂,已用于茶叶样品中微量钡的测定,结果与原子吸收光度法相一致。     

茶叶掺糖含量检测算法中光谱数据有效性及冗余度研究

基于近红外光谱(NIRS)技术和遗传算法-反向传播(GA-BP)神经网络建立模型，分析茶叶掺蔗糖样品的1～2.5 μm原始光谱数据的有效性及冗余度。固定样本数据，对模型的参数优化选择后建立茶叶蔗糖含量定量检测模型。将1～2.5 μm原始数据分1～1.7，1～1.3，1.3～1.7，1.7～2.5和2～2.2 μm。利用建立的模型对同一分辨率下的不同波段进行模型训练。预测结果表明，1～1.7和1～2.5 μm波段存在数据冗余。仅使用1.3～1.7或1.7～2.5 μm波段即可有效建立模型。预测模型对同一波段下的不同分辨率进行研究，从2 nm到20 nm改变分辨率，当波段范围为1～2.5 μm时，模型的R均介于0.9和0.95之间，且RMSEP也在1.7和2.1之间。当波段范围为1～1.7 μm时，模型的R均在0.9和0.93之间，且RMSEP也在1.95和2.25之间。结果表明，1～2.5 μm原始数据中确实存在波长范围和光谱分辨率的冗余。通过光谱特征分析和算法建模，可以显著提高光谱数据获取的有效性；对于茶叶中蔗糖含量的检测，可以采用更窄的波长范围和更低的光谱分辨率。     

基于X射线荧光技术的茶叶产地鉴别方法研究

针对目前市场上存在的产地假冒茶叶严重影响名牌茶叶信誉的情况,根据不同产地茶叶中重金属含量的差异,提出了利用X射线荧光技术结合模式识别技术进行了茶叶产地鉴别的方法。将不同产地的样本分组,分别采集其X射线荧光光谱,提取其主成分,分别计算各个样本组的主成分均值作为样本中心点,计算待测样本到各样本组中心的马氏距离,将其归类到马氏距离值最小的类中,实现样本分类。采用Niton 792便携式X射线荧光仪对安吉、金华、杭州和台州等4个不同地区120个茶叶样本进行了鉴别试验,发现3～13 keV波段是X射线荧光光谱分析技术进行茶叶产地鉴别的有效波段,前4个主成分可用于茶叶的产地鉴别,试验的误差率为4.2%。     

Streamlining sample preparation and gas chromatography–tandem mass spectrometry analysis of multiple pesticide residues in tea

In this work, a new rapid method for the determination of 135 pesticide residues in green and black dry tea leaves and stalks employing gas chromatography coupled to tandem mass spectrometry (GC–MS/MS) with a triple quadrupole was developed and validated. A substantial simplification of sample processing prior to the quantification step was achieved: after addition of water to a homogenised sample, transfer of analytes into an acetonitrile layer was aided by the addition of inorganic salts. Bulk co-extracts, contained in the crude organic extract obtained by partition, were subsequently removed by liquid–liquid extraction using hexane with the assistance of added 20% (w/w) aqueous NaCl solution. The importance of matrix hydration prior to the extraction for achieving good recoveries was demonstrated on tea samples with incurred pesticide residues. For most of the analytes, recoveries in the acceptable range of 70–120% and repeatabilities (relative standard deviations, RSDs) ≤20% were achieved for both matrices at spiking levels of 0.01, 0.1 and 1 mg kg⁻¹. Under optimised GC–MS/MS conditions, most of the analytes gave lowest calibration level ≤0.01 mg kg⁻¹, permitting the control at the maximum residue levels (MRLs) laid down in Regulation (EC) No 396/2005. The developed method was successfully applied to the determination of pesticide residues in real tea samples.     

Evaluation of tea tree oil quality and ascaridole: A deep study by means of chiral and multi heart-cuts multidimensional gas chromatography system coupled to mass spectrometry detection

The natural-like assessment of essential oils is a demanding task due to the growing trend toward adulterations. Usually chiral chromatography was used for this purpose due to the capability of assessing stereospecificity which is directly related to the enzymatic pathways of each plant species. On the other hand, the quality of an essential oil involves also the evaluation of its oxidative state, mainly connected with the age and storage conditions. In fact, some modifications in the chemical profile of the oil can occur if not properly preserved. Alterations of the components due to oxidative reactions lead to the formation of peroxides, endoperoxides and epoxides, such as ascaridole and 1,2,4-trihydroxymenthane, usually present in very low amount, formed by the oxidation of terpinen-4-ol and α-terpinene, respectively. Therefore, in the present research, the quality of Australian Tea Tree oil (Melaleuca alternifolia (Maiden & Betche) Cheel, Myrtaceae) was investigated by means of a multi heart-cut multidimensional gas chromatographic system coupled to a mass spectrometer detector and by conventional enantio-GC. The MDGC system allowed the complete separation of the compounds of interest transferred from the first column to a second dimension based on a different separation mechanism. The MS detector at the end of the second column provided the identification of the peaks with high similarity values because of their high purities after the multidimensional separation. Method validation was carried out, in order to use this procedure for routine application, monitoring the repeatability of 1D retention times and 2D peak areas, LoD and LoQ. Finally, enantiomeric ratios for chiral compounds were established to support quality data obtained.     

Development and application of UHPLC-MS/MS method for the determination of phenolic compounds in Chamomile flowers and Chamomile tea extracts

UHPLC-MS/MS method using BEH C18 analytical column was developed for the separation and quantitation of 12 phenolic compounds of Chamomile (Matricaria recutita L.). The separation was accomplished using gradient elution with mobile phase consisting of methanol and formic acid 0.1%. ESI in both positive and negative ion mode was optimized with the aim to reach high sensitivity and selectivity for quantitation using SRM experiment. ESI in negative ion mode was found to be more convenient for quantitative analysis of all phenolics except of chlorogenic acid and kaempherol, which demonstrated better results of linearity, accuracy and precision in ESI positive ion mode. The results of method validation confirmed, that developed UHPLC-MS/MS method was convenient and reliable for the determination of phenolic compounds in Chamomile extracts with linearity >0.9982, accuracy within 76.7-126.7% and precision within 2.2-12.7% at three spiked concentration levels. Method sensitivity expressed as LOQ was typically 5-20 nmol/l.Extracts of Chamomile flowers and Chamomile tea were subjected to UHPLC-MS/MS analysis. The most abundant phenolic compounds in both Chamomile flowers and Chamomile tea extracts were chlorogenic acid, umbelliferone, apigenin and apigenin-7-glucoside. In Chamomile tea extracts there was greater abundance of flavonoid glycosides such as rutin or quercitrin, while the aglycone apigenin and its glycoside were present in lower amount.     

Study the effect of metal ion on wool fabric dyeing with tea as natural dye

Aqueous extract of natural dye, tea was dyed on the wool fabric with dark brown for 2% and 5% shade. The tea containing tannins as the main colorant species to produce different shade with different mordant salts. The mordant salts Alum, CuSO₄, FeSO₄, ZnSO₄, Na₂SO₄, and MgSO₄ were used to dye fabric using three different dyeing methods: pre-mordanting, meta-mordanting and post-mordanting. The color of the fabric was investigated on Data Color matching system in terms of K/S and CIE Lab-color difference values. The post-mordanting method gave the great depth of shade of natural dye tea with 2% and 5% shade, it also give good light fastness and wash fastness properties. Copper was found as a good mordant to achieve the best results with transition metal ions effect. Deep shades (K/S = 17.50) were obtained for original sample of 5% with color difference ΔE value is 0.17, as compare to 2% original sample of tea of light brown shades (K/S = 10.50) with color difference ΔE value is 0.50 under maintained temperature at 85 °C for 35 min of dyeing.