密胺餐具中三聚氰胺的迁移规律

密胺餐具样品用乙酸溶液浸泡后,采用高效液相色谱法测定其中三聚氰胺的迁移量。考察了浸泡液的种类、浸泡温度、浸泡时间、样品尺寸、浸泡次数等参数对三聚氰胺迁移量的影响。试验结果表明:三聚氰胺的迁移量随溶液酸性、浸泡温度、浸泡时间的增加及样品尺寸的减小而增大;随浸泡次数的增多,每次浸出量递减。     

金银花茶中8种微量元素溶出特性研究

目的 探究金银花茶样品中8种微量元素的溶出特性。方法 基于电感耦合等离子体质谱法(inductively coupled plasma mass spectrometry,ICP-MS),测定样品中Na、Ca、Mg、Mn、Fe、Zn、Cu、Se 8种微量元素含量,并分别研究了浸泡时间、浸泡次数及浸泡温度与元素溶出特性之间的关系。结果 结果表明,金银花茶中微量元素含量丰富,8种元素含量由高到低的顺序为：Ca>Mg> Fe>Na>Mn> Zn>Cu>Se。各元素溶出量随浸泡时间延长而升高,其中Fe溶出率最低,表明Fe最难溶出。除Na和Se以外,各元素溶出量随浸泡次数增加而降低,随浸泡温度升高而升高;Na的溶出量随浸泡次数增加呈先降低后升高的趋势,而Se的溶出量随浸泡次数增加而降低;Na和Se的溶出量均随浸泡温度升高呈先升高再降低的趋势。各元素溶出量与浸泡时间、浸泡次数及浸泡温度之间的关系均可通过建立不同类型的数学模型进行描述。结论 从保健茶饮的功能性和风味角度考虑,金银花茶冲泡应选用100℃的水温,且冲泡次数应不超过4次。     

自来水用橡胶软管中铅的析出分析

研究生活饮用水用橡胶软管中铅析出规律,选择3款橡胶软管,测定铅含量,并在自来水中分析不同浸泡时间以及普通浸泡温度(22、40、60、80、100℃)条件下铅析出量。结果表明,橡胶软管3#、1#、2#的铅含量依次降低,相同条件下铅析出量也依次降低;同一样品随着浸泡次数的增加,铅析出量呈现下降趋势;随着温度的升高,铅析出量呈现增加趋势,析出速率也在增加,铅含量高的橡胶软管铅析出量也高,铅析出量随着浸泡次数的增加而逐渐降低,随着浸泡温度的提高而增高。     

稀土废渣中污染物特性及环境风险分析

探究了离子型稀土矿开采产生的除杂渣、酸溶渣、熔盐渣3种典型稀土废渣的腐蚀性、组成、物相结构及赋存状态。基于典型稀土废渣的赋存状态及其堆存自然环境,研究了浸泡时间、浸泡液pH值和浸泡温度等因素对其所含铜、锌、铅、镉、镍、总铬、铍、钡、砷、硒等重金属离子及镝,铒,钆,钬,钕,镨,钐,镱稀土元素的浸出含量的影响,分析和评估了除杂渣、酸溶渣、熔盐渣3种典型稀土废渣的有毒重金属离子浸出毒性和环境风险,为稀土废渣的回收利用和安全处置提供了数据支撑。     

湛江市不同茶场出品的绿茶茶水中微量元素的测定分析

采用原子吸收法测定了湛江不同茶场出品的绿茶茶水中的锌、铜、铁、钙、镁、锰、镉、镍、铅的含量。结果显示，绿茶茶水中含有较丰富的多种矿物元素和人体必需的微量元素，不同茶场出品的绿茶茶水中微量元素含量有所不同，浸泡次数不同，微量元素含量不同，第一次浸泡的茶水中微量元素的含量明显大于第二次浸泡。     

ICP-MS法测定硅胶奶嘴中8种可溶性重金属

建立了使用电感耦合等离子体-质谱仪技术(ICP-MS)分析硅胶奶嘴中锰、镍、铜、锌、镉、铅、铬、砷溶出量的方法.应用碰撞反应界面技术(CRI)有效地消除了多原子或离子对待测金属离子的干扰;选用89 Y,115In和209Bi等元素为内标混合液校正基体效应和信号漂移,确定了实验的最佳测定条件;研究了浸泡温度、浸泡时间以及浸泡提取方式对重金属溶出量的影响.该测试方法对于锰、镍、铜、锌、镉、铅、铬、砷的仪器检出限为0.01~2.00μg/L,仪器相对标准偏差为0.4%~2.8%,加标回收率为81.4%~113.1%.该方法快速、简便,具有较好的准确度和精密度,为硅胶奶嘴中重金属含量的监控提供了途径.     

银杏茶中总黄酮的水溶浸出行为研究

以芦丁为标准品，采用分光光度法，以Al（NO3）3-NaNO2为显色剂，测定了市售银杏茶中总黄酮的含量，并考察了银杏茶在水中浸泡时浸泡温度、浸泡时间、浸泡次数、浸泡溶液的pH值等条件对银杏茶中总黄酮浸出的影响。结果表明，银杏茶中黄酮在水中浸出量受浸泡温度和浸泡溶液DH值的影响比较大。泡茶的溶液应避免使用酸性溶液。还对银杏茶的加工工艺进行了考察研究，发现银杏叶通过微波处理后，其黄酮的浸出量明显高出烘箱烘干的银杏叶的黄酮浸出量。因此，建议在银杏茶的加工工艺中采用微波干燥处理银杏叶。     

橡胶软管在自来水中铅析出分析

目的 研究生活饮用水用橡胶软管中铅析出规律。方法 选择3款橡胶软管,测定铅含量,并在自来水中分析不同浸泡时间以及不通浸泡温度(22、40、60、80、100 ℃)条件下铅析出量。结果 橡胶软管3_^#、1_^#、2_^#的铅含量依次降低,相同条件下铅析出量也依次降低;同一样品随着浸泡次数的增加,铅析出量呈现下降趋势;随着温度的升高,铅析出量呈现增加趋势,析出速率也在增加。结论 铅含量高的橡胶软管铅析出量也高,铅析出量随着浸泡次数的增加而逐渐降低,随着浸泡温度的提高而增高。     

高温灼烧除硫-火焰原子吸收光谱法连续测定硫精矿和硫渣中的铜、镉、铅、锌

试样在800℃的马弗炉中灼烧除硫,用王水溶解,上清液用原子吸收光谱仪于波长324.7,228.8,283.3,213.8nm处,用空气-乙炔火焰分别测量铜、镉、铅、锌的含量。方法适用于直接浸出渣中的硫渣、硫精矿中铜、铅、锌、镉含量的测定。测定范围:铜0.025%~0.50%,镉:0.025%~0.50%,铅:0.26%~5%,锌:1.0%~10.00%。     

电镀液中铜、铁、铅和锌等杂质元素的原子吸收光谱测定

电镀液中常见的有害杂质:铜、铁、铅和锌等的允许含量随镀液种类和杂质元素不同而异。例如,镀镍液中的铜、铁、铅和锌的允许范围在几个至几十个毫克/升内,而镀铬液中的铁的允许范围却在1—几克/升内。1964年Whittington报告用原子吸收加入法测镀镍液中的铜、铁、铅和锌。我们也用过此法。此法比较麻烦。虽然Parker报告把电镀液稀释后直接用原子吸收法测锌、铜、铬,但未报导具体条件。本文除测定镀镍液和镀钻液中低含量铁仍用加入法外,铜、铅、锌及镍、钴镀液中高于50毫克/升铁都用稀释法。实验表明:     

茶叶中咖啡因的提取实验装置的改进与探索

"茶叶中咖啡因的提取"是有机化学实验的一个经典实验,本文对该实验所用的原索氏提取器进行改进,得到内通气集热式索氏提取器并用于实验教学。通过对照实验,对改进索氏提取器和原索氏提取器的提取效果进行比较。结果表明,改进装置具有原装置的功能和特点,且提取时间更短、提取温度和提取率更高,可在高校推广使用。     

Optimum Ultrasound Assisted Extraction Conditions of Some Flavonoids from Green Tea Leaves. Control Quality of Green Tea Product by TLC Fingerprinting

The optimization of the green tea flavonoid extraction conditions was investigated. The experiments were carried out with two extraction methods: ultrasound assisted extraction (UAE) and reflux extraction (RE). The parameters that were varied in this study were: the extraction solvent system composition, the type of organic modifier of the extraction mixture, temperature, and time. The highest efficiency was obtained with an extraction mixture of ethanol: water, 80:20, v/v. An extraction performed at temperature of 45°C in 50–60 minutes led to optimum results. Moreover, a new fingerprinting procedure based on thin layer chromatography (TLC) image analysis was employed in order to compare the chemical composition of green tea in comparison with white and black tea.     

Optimizing conditions for the extraction of catechins from green tea using hot water

Six different factors involved in the extraction of catechins from green tea using water were examined for their impact on the yield of catechins and on the efficiency of water use. The best temperature and time combination for catechin extraction was at 80°C for 30 min. The yield of catechins was also optimal with a tea particle size of 1 mm, a brewing solution pH <6 and a tea‐to‐water ratio at 50:1 (mL/g). In terms of efficient use of water in a single extraction, a water‐to‐tea ratio of 20:1 (mL/g) gave the best results; 2.5 times less water was used per gram of green tea. At the water‐to‐tea ratio of 20:1 mL/g, the highest yield of catechins per gram of green tea was achieved by extracting the same sample of green tea twice. However, for the most efficient use of water, the best extraction was found to be once at a water‐to‐tea ratio of 12:1 (mL/g) and once at a water‐to‐tea ratio of 8:1 (mL/g). Therefore, all six of the factors investigated had an impact on the yield of catechins extracted from green tea using water and two had an impact on the efficiency of water use.     

Application of mesoporous carbon as a solid‐phase microextraction fiber coating for the extraction of volatile aromatic compounds

A mesoporous carbon was fabricated using MCM‐41 as a template and sucrose as a carbon source. The carbon material was coated on stainless‐steel wires by using the sol–gel technique. The prepared solid‐phase microextraction fiber was used for the extraction of five volatile aromatic compounds (chlorobenzene, ethylbenzene, o‐xylene, bromobenzene, and 4‐chlorotoluene) from tea beverage samples (red tea and green tea) prior to gas chromatography with mass spectrometric detection. The main experimental parameters affecting the extraction of the volatile aromatic compounds by the fiber, including the extraction time, sample volume, extraction temperature, salt addition, and desorption conditions, were investigated. The linearity was observed in the range from 0.1 to 10.0 μg/L with the correlation coefficients (r) ranging from 0.9923 to 0.9982 and the limits of detection were less than 10.0 ng/L. The recoveries of the volatile aromatic compounds by the method from tea beverage samples at spiking levels of 1.0 and 10.0 μg/L ranged from 73.1 to 99.1%.     

Optimum conditions for the water extraction of L-theanine from green tea

Theanine is a unique non-protein amino acid found in tea (Camellia sinensis). It contributes to the favourable umami taste of tea and is linked to various beneficial effects in humans. There is an increasing interest in theanine as an important component of tea, as an ingredient for novel functional foods and as a dietary supplement. Therefore, optimal conditions for extracting theanine from tea are required for the accurate quantification of theanine in tea and as an efficient first step for its purification. This study examined the effects of four different extraction conditions on the yield of theanine from green tea using water and applied response surface methodology to further optimise the extraction conditions. The results showed that temperature, extraction time, ratio of water-to-tea and tea particle sizes had significant impacts on the extraction yield of theanine. The optimal conditions for extracting theanine from green tea using water were found to be extraction at 80 °C for 30 min with a water-to-tea ratio of 20:1 mL/g and a tea particle size of 0.5-1 mm.     

Effects of different extraction methods and conditions on the phenolic composition of mate tea extracts

A simple and rapid HPLC method for determination of chlorogenic acid (5-O-caffeoylquinic acid) in mate tea extracts was developed and validated. The chromatography used isocratic elution with a mobile phase of aqueous 1.5% acetic acid-methanol (85:15, v/v). The flow rate was 0.8 mL/min and detection by UV at 325 nm. The method showed good selectivity, accuracy, repeatability and robustness, with detection limit of 0.26 mg/L and recovery of 97.76%. The developed method was applied for the determination of chlorogenic acid in mate tea extracts obtained by ethanol extraction and liquid carbon dioxide extraction with ethanol as co-solvent. Different ethanol concentrations were used (40, 50 and 60%, v/v) and liquid CO? extraction was performed at different pressures (50 and 100 bar) and constant temperature (27 ± 1 °C). Significant influence of extraction methods, conditions and solvent polarity on chlorogenic acid content, antioxidant activity and total phenolic and flavonoid content of mate tea extracts was established. The most efficient extraction solvent was liquid CO? with aqueous ethanol (40%) as co-solvent using an extraction pressure of 100 bar.     

顶空固相微萃取结合气相色谱-三重四极杆质谱法快速测定茶叶中11种酰胺类除草剂残留

利用顶空固相微萃取(HS-SPME)与气相色谱-三重四极杆质谱(GC-MS/MS)联用,建立了快速测定茶叶中11种酰胺类除草剂残留的检测方法。以全发酵红茶为基质,对影响萃取性能的因素(如萃取涂层种类、无机盐种类、水用量、盐用量、萃取温度和萃取时间)进行了优化。在最优条件下,选取绿茶、乌龙茶、红茶和普洱茶4种茶叶基质对方法学进行考察。结果表明,11种酰胺类农药在1~1 000μg/kg含量范围内线性关系良好,相关系数(r2)为0.992 5~0.999 9,定量下限为1~10μg/kg。11种农药在红茶、绿茶、乌龙茶和黑茶基质中3个添加水平下的平均回收率分别为70.3%~119.1%、85.2%~118.7%和74.6%~113.3%,相对标准偏差(RSD)均不大于17.4%。该方法操作简单、快速、灵敏度高、重现性好,可满足不同种类茶叶基质中11种酰胺类除草剂农药残留的检测要求。     

Dynamic hollow fiber protected liquid phase microextraction and quantification using gas chromatography combined with electron capture detection of organochlorine pesticides in green tea leaves and ready-to-drink tea

The dynamic hollow fiber protected liquid phase microextraction (DHFP-LPME) technique was evaluated for the extraction of organochlorine pesticides (OCPs) in green tea leaves and ready-to-drink tea prior to gas chromatography combined-electron capture detection (GC-ECD) analysis. A conventional microsyringe with a 1.5 cm length of hollow fiber attached to its needle was connected to a syringe pump to perform the extraction. The microsyringe was used as both the microextraction device and the sample introduction device for GC-ECD analysis. In this work, the organochlorine pesticides were extracted and condensed to a volume of 3 microl of organic extracting solvent (1-octanol) confined within a 1.5 cm length of hollow fiber. The effects of extraction solvent, extraction time, sample agitation, plunger speed, and extraction temperature and salt concentration content on the extraction performance were also investigated. Good enrichments were achieved (34-297-fold) with this method, and good repeatabilities of extraction were obtained, with full name (RSDs) below 12.57%. Detection limits were much below 1 microg l(-1) for ready-to-drink tea and much below 1 microg g(-1) for green tea leaves.     

不同提取方法对红茶提取物抗氧化活性影响的研究

采取沸水浴法、回流法、微波法及超声波法探讨信阳红茶和印度红茶的抗氧化性,通过测定吸光度利用Fenton反应表征提取物对羟自由基的清除率.不同的提取方法对红茶抗氧化活性有一定的影响,羟自由基的清除率与红茶的抗氧化活性成正比.结果表明:信阳红茶沸水浴法提取率较高,印度红茶超声波法提取率较高.     

Stir bar sorptive extraction and high-performance liquid chromatography-fluorescence detection for the determination of polycyclic aromatic hydrocarbons in Mate teas

A simple procedure based on stir bar sorptive extraction (SBSE) and high-performance liquid chromatography-fluorescence detection (HPLC-FLD) is presented for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in herbal tea prepared with Mate leaves (Ilex paraguariensis St. Hil.). The influence of methanol and salt addition to the samples, the extraction time, the desorption time and the number of desorption steps, as well as the matrix effect, were investigated. Once the SBSE method was optimised (10 mL of Mate tea, 2h extraction at room temperature followed by 15 min desorption in 160 microL of an acetonitrile (ACN)-water mixture), analytical parameters such as repeatability (< or = 10.1%), linearity (r2 > or = 0.996), limit of detection (LOD, 0.1-8.9 ng L(-1) ), limit of quantitation (LOQ, 0.3-29.7 ng L(-1) and absolute recovery (24.2-87.0%) were determined. For calibration purposes, a reference sample was firstly obtained by removing the analytes originally present in the lowest contaminated Mate tea studied (via SBSE procedure) and then spiked at 1-1200 ng L(-1)range. The proposed methodology proved to be very convenient and effective, and was successfully applied to the analysis of 11 Mate tea samples commercialised in Brazil. The results of the commercial Mate tea samples found by the SBSE approach were compared with those obtained by liquid-liquid extraction (LLE), showing good agreement.