超声波法提取苦丁茶总黄酮含量的工艺

采用超声波提取法,通过单因素实验和正交试验优选出苦丁茶中总黄酮的最佳提取工艺.苦丁茶总黄酮最佳提取工艺为:料液比(g/mL)1:30,乙醇浓度70%,超声功率80W,提取时间20min.在此条件下,苦丁茶中的总黄酮含量为21.151mg/g,RSD=0.85%(n=3).     

Polarized X ray fluorescence spectrometer (EDPXRF) for the determination of essential and non essential elements in tea

Polarized X ray fluorescence spectrometer (EDPXRF) is employed for the determination of essential and non essential elements in several kinds of tea marked in Italy. The quality of data was assured by calibrating the instrument with certified reference materials. The elements are found to be present in the different kinds of tea in various proportions depending on soil composition and the climate in which the plant grows.     

氢化物发生-原子荧光光谱法测定茶水中砷

采用氢化物发生-原子荧光光谱法测定茶水中砷含量。样品经硝酸-高氯酸(4+1)混合酸消解,在盐酸(6+94)溶液中加入30 g·L-1硼氢化钾-5 g·L-1氢氧化钾溶液使与溶液中砷离子反应生成氢化物。分析中采用载气流量为400 mL·min-1。试样溶液中加入硫脲及抗坏血酸混合溶液作为预还原剂。引入仪器的进取样量为1.2 mL,按选定的工作条件操作。荧光强度与砷的质量浓度在0.20~100μg·L-1范围内呈线性关系,方法的检出限(3s/k)为0.030μg·L-1。应用此法对3种茶叶泡出的茶水进行分析,测得回收率在97.7%~101.5%之间。     

固相萃取-气相色谱法测定茶叶中多种有机磷农药残留量

本文选择石墨碳黑固相萃取小柱对茶叶样品进行净化,样品中残留的农药经过乙腈洗脱,浓缩后采用气相色谱-火焰光度检测器(FPD)测定.研究结果表明,茶叶中添加农药浓度为0.02～1.0 mg/kg时,9种农药的平均回收率为75.76%～107.9%,相对标准偏差为1.38%～8.95%,方法检出限为0.006～0.01 mg...     

高效液相色谱-串联质谱法测定茶叶中唑螨酯、三唑酮、鱼藤酮、除虫脲及萎锈灵残留量

提出了高效液相色谱-串联质谱法同时测定茶叶中5种农药,即唑螨酯、三唑酮、鱼藤酮、除虫脲和萎锈灵残留量的方法。样品经乙腈和固体硫酸镁及氯化钠提取,以Shiseido C18MGII色谱柱为分离柱,以不同体积比的乙腈和0.005mol·L-1乙酸铵溶液的混合液为流动相进行梯度洗脱。采用电喷雾正离子源多反应监测模式进行质谱测定。5种农药的质量浓度均在1.00~20.0μg·L-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)为0.005 mg·kg-1。在0.005,0.010,0.020mg·kg-1 3个浓度水平上进行加标回收试验,回收率在88.2%~104%之间,测定值的相对标准偏差(n=10)在4.8%~13%之间。     

Tea and fluorosis

Tea trees (Camellia sinensis), abundant in fluoride, selectively absorb F from the soil and air in the surrounding, and accumulate mainly in the tea leaves in the form of Al and F complex. Long-term consumption of high fluoride tea could result in chronic fluoride intoxication. This review summarized those data of the fluoride content in various tea commodities, and estimated the risk of fluorosis caused by high fluoride tea commodities. We also introduced fluorosis caused by tea from case reports, epidemiology observations and animal models. Fluorosis was easily misdiagnosed and over-looked and people made little acquaintance in the high fluoride in some tea commodities. So it is the time to pay more attentions on the over-looked safety problem of tea and tea products and some measures should be taken to the fluorosis caused by tea. Large-scale epidemiological investigations and further studies on tea-type fluorosis are in need for those tea-drinking areas. In addition, it is urgent that governmental and international agencies adopt safe standards of fluoride content in tea commodities.     

Solid‐phase purification and extraction for the determination of trace neonicotinoid pesticides in tea infusion

An analytical protocol that includes solid‐phase purification and extraction is successfully developed for the determination of trace neonicotinoid pesticides in tea infusion. The method consists of a purification on amino‐functionalized mesoporous silica SBA‐15 followed by a solid‐phase extraction based on graphene oxide before ultra high performance liquid chromatography with tandem mass spectrometry analysis. Parameters that significantly affected the extraction of the neonicotinoids onto graphene oxide, such as the amount of adsorbent, extraction time, pH, elution solvent, etc. were optimized. The amino‐functionalized mesoporous silica SBA‐15 has been proved to be an efficient adsorbent for removal of polyphenols especially catechins from tea infusion. Graphene oxide exhibits a very rapid adsorption rate (within 10 min) and high adsorption capacities for neonicotinoids at low initial concentration (0.01–0.5 mg/L). The analysis method gave a good determination coefficient (r² > 0.99) for each pesticide and high recoveries in the range of 72.2–95.0%. Powder X‐ray diffraction, Raman spectroscopy, transmission electron microscopy, and UV‐vis spectroscopy were utilized to identify the structure and morphology of graphene oxide. The adsorption driving force of neonicotinoids on graphene oxide mainly depends on π–π electron donor–acceptor interaction and electrostatic interaction.     

Synthesis of molecularly imprinted polymers using acrylamide‐β‐cyclodextrin as a cofunctional monomer for the specific capture of tea saponins from the defatted cake extract of Camellia oleifera

Molecularly imprinted polymers were synthesized using mixed tea saponins as a template and acrylamide‐β‐cyclodextrin as a cofunctional monomer for the specific binding and purification of tea saponins from the defatted cake extract of Camellia oleifera. The adsorption properties of the prepared polymers were systematically evaluated including adsorption kinetics, adsorption isotherms, and selective recognition characteristics. It showed that the adsorption kinetics followed the pseudo first‐order kinetic model (R² = 0.995) with an equilibrium time of 3 h, adsorption isotherm data fitted well with the Langmuir–Freundlich model (R² = 0.984) with an adsorption capacity of 14.23 mg/g. The relative selectivity coefficient (k´) in the presence of the analogues glycyrrhizic acid and glycyrrhetinic acid were 1.16 and 17.21, respectively. The performance of the molecularly imprinted polymers as solid‐phase extraction materials was investigated and the results indicated that using acrylamide‐β‐cyclodextrin as a cofunctional monomer improved both the adsorption capacity and active sites stability of the imprinted polymers. The solid‐phase extraction using the polymers as packing materials was subsequently applied for the separation of tea saponins in raw C. oleifera press extract, and targets were obtained with a purity reaching 89%.     

固相萃取-气相色谱法测定茶叶中甲胺磷残留量

茶叶样品经乙酸乙酯提取,上清液于50℃蒸发至近干,加入乙酸乙酯溶解残渣后,经硅胶-石墨化碳混合柱净化。先以乙酸乙酯洗脱去除杂质,再以碱化乙腈洗脱并收集流出液,在50℃蒸发至近干,加乙酸乙酯定容至1mL,供气相色谱分析。采用DB-1701色谱柱分离和火焰光度检测器检测,所得甲胺磷的线性范围为0.010～1.00mg·L-1,方法的检出限(3S/N)为0.005mg·kg-1。在0.010,0.020,0.080 mg·kg-1 3个浓度水平下进行回收试验,甲胺磷的回收率在85.0%～90.9%之间,相对标准偏差(n=6)在2.2%～4.3%之间。