改进的氧瓶燃烧法结合电感耦合等离子体质谱快速测定茶叶样品中的稀土元素含量

建立了电感耦合等离子体质谱法快速测定茶叶中Y~Lu共15种稀土元素的新方法,样品处理基于改进的氧瓶燃烧法,以涂覆甘油的石英布代替滤纸作为引燃和燃烧载体,在500 mL容积燃烧瓶中实现了0.1 g样品量的有氧完全燃烧。系统优化了样品处理关键参数,以5 mL 4％ HNO3+1％ HF(V/V)组合试剂超声提取燃烧残渣1 min,稀土元素回收率大于90％,样品总处理周期小于3 min。6次样品平行测定值的相对标准偏差(RSD)在2.7％~5.5％之间,方法检出限(3σ)在0.001~0.006 mg/kg之间。采用本方法对3种茶叶标准参考物质进行分析,测定结果和标准值吻合良好。     

Magnetically separable tea leaf mediated nickel oxide nanoparticles for excellent photocatalytic activity

Synthesis of nanoparticles having low chemical toxicity has been interest of researchers for decades. Utilization of plant phytochemicals as reducing agent is now a globally recognized alternative technique for environmental friendly and low-cost production of nanoparticles. This work reports a facile green synthesis protocol of Nickel Oxide nanoparticles (NiO NPs) using fresh tea leaf extract. The synthesized nanoparticles have been characterized through various analytical techniques like Powder XRD (P-XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The XRD results reveal the formation of crystalline nickel oxide nanoparticles. FTIR spectrum displays the existence of different polyphenolic groups over NiO NPs surface. TEM and SEM images indicate the formation of slightly agglomerated spherical nanoparticles with particle size 3–5 ​nm. The nanoparticles were used towards the photocatalytic degradation of both cationic, anionic dyes and their mixtures under optimum conditions in the presence of UV light irradiation. More than 95% degradation was observed for all the dye solutions with 30 ​mg ​L^-1 catalytic dose. Moreover, the degradation efficiency of the nanoparticle was studied by altering various parameters like pH, initial dye concentration and amount of catalytic dose. Pseudo first order kinetic model was employed in all the reactions. A detailed mechanism and kinetics of the all the reactions were studied. Interestingly, the catalyst showed excellent recyclability up-to 4th cycles with very low catalytic activity loss.     

ICP-OES测定奶茶粉中的常量、微量元素

采用干法灰化法处理奶茶粉样品,建立电感耦合等离子体发射光谱法(ICP-OES)同时测定奶茶粉中常量、微量元素的方法.该方法以钪作为内标以补偿仪器波动,采用不同标准系列分组以消除光谱干扰.方法检出限为0.02-8.77μg/g,相对标准偏差均小于3%,回收率为93.9%-109.4%.方法操作简单、分析速度快、灵敏度高、...     

Removal of methylene blue by tea wastages from the synthesis waste waters

The tea wastages could remove methylene blue（MB） as a cationic dye from waste water corresponding to second-order kinetic model.Thermodynamic studies showed that adsorption equilibrium constant（K_L） and maximum adsorption capacities(Q_max) were increased with increasing temperature.The removal efficiency of MB for Co 0.01 mmol/L at optimum conditions was about 85%. The maximum uptake capacity(Q_max) of methylene blue in a batch reactor was 0.328,0.542 and 0.659 mmol/g at 15,25 and 40℃, respectively.The enthalpy change（ΔH） and entropy change（ΔS） were 11.356 kJ/mol and 20.563 J/（mol K）,respectively.     

Emerging applications of nano-optical sensors combined with near-infrared spectroscopy for detecting tea extract fermentation aroma under ultrasound-assisted sonication

The current innovative work combines nano-optical sensors with near-infrared spectroscopy for rapid detection and quantification of polyphenols and investigates the potential of the nano-optical sensor based on chemo-selective colorants to detect the dynamic changes in aroma components during the fermentation of tea extract. The procedure examined the influence of different ultrasound-assisted sonication factors on the changes in the consumption rate of polyphenols during the fermentation of tea extract versus non-sonication as a control group. The results showed that the polyphenol consumption rate improved under the ultrasound conditions of 28 kHz ultrasound frequency, 24 min treatment time, and 40 W/L ultrasonic power density. The metal–organic framework based nano-optical sensors reported here have more adsorption sites for enhanced adsorption of the volatile organic compounds. The polystyrene-acrylic microstructure offered specific surface area for the reactants. Besides, the employed porous silica nanospheres with higher porosity administered improved gas enrichment effect. The nano-optical sensor exhibits good performance with a “chromatogram” for the identification of aroma components in the fermentation process of tea extract. The proposed method respectively enhanced the consumption rate of polyphenol by 35.57%, 11.34% and 16.09% under the optimized conditions. Based on the established polyphenol quantitative prediction models, this work demonstrated the feasibility of using a nano-optical sensor to perform in-situ imaging of the fermentation degree of tea extracts subjected to ultrasonic treatment.     

Development and Application of a Hydride Generation Laser Induced Fluorescence Method for Measurements of Bismuth

A hydride generation laser induced fluorescence (HG LIF) approach has been investigated for trace level measurements of bismuth. The technique uses a tunable dye laser operating at 306.7 nm as the excitation source and bismuth fluorescence is measured at 472 nm. The optimized HCl and NaBH₄ concentrations for bismuth measurements were 1.2 M and 2.0%, respectively. The current technique has a limit of detection of 0.03 ppb and 0.01 ppb for blank measurements performed with the laser tuned on and off the bismuth excitation wavelength, respectively. Measurements of bismuth in different sample matrices have demonstrated the effectiveness of thiourea and ascorbic acid as masking agents for measuring samples containing interfering ions. Measurements of bismuth have been performed in reference materials, a bismuth-containing medication, and tea leaves. The results demonstrate that the HG LIF approach has feasibility for measuring bismuth in various samples at environmentally relevant concentrations.     

Development of a candidate certified reference material of cypermethrin in green tea

This paper presents the preparation of a candidate certified reference material (CRM) of cypermethrin in green tea, GLHK-11-01a according to the requirements of ISO Guide 34 and 35. Certification of the material was performed using a newly developed isotope dilution mass spectrometry (IDMS) approach, with gas chromatography high resolution mass spectrometry (GC–HRMS) and gas chromatography–tandem mass spectrometry (GC–MS/MS). Statistical analysis (one-way ANOVA) showed excellent agreement of the analytical data sets generated from the two mass spectrometric detections. The characterization methods have also been satisfactorily applied in an Asia-Pacific Metrology Program (APMP) interlaboratory comparison study. Both the GC–HRIDMS and GC–IDMS/MS methods proved to be sufficiently reliable and accurate for certification purpose. The certified value of cypermethrin in dry mass fraction was 148 μg kg⁻¹ and the associated expanded uncertainty was 14 μg kg⁻¹. The uncertainty budget was evaluated from sample in homogeneity, long-term and short-term stability and variability in the characterization procedure. GLHK-11-01a is primarily developed to support the local and wider testing community on need basis in quality assurance work and in seeking accreditation.     

Determination of Total and Fluoride Bound Aluminium in Tea Infusions by Ion Selective Electrode and Flame Atomic Absorption Spectrometry

ABSTRACT

Speciation of metallic compunds is important especially for their bioavailability. In this present study fluoride bound aluminium species were determined in tea infusion. Total aluminium was measured using flame atomic absorption spectrometry (FAAS). Free fluoride and total fluoride were measured by fluoride selective ion electrode (FISE) with the assistance of TISAB buffer solution used for adjustment of pH and total ionic strength, and ALCOA buffer solution which decomposes all of the Al-fluoride complexes in solution.

During the studies, the effects of pH and time on the formation of Al-F complexes and interference of some metal ions found in tea infusion such as Al³⁺, Mg²⁺, Fe²⁺, Fe³⁺ and Mn²⁺ on the concentration of free fluoride were investigated. The concentration of each Al-fluoride complexes in tea fusion were determined indirectly by calculation using pF-Mole Fraction Diagram. It was found that 1.13±0.15 mg 1^? of 12.00±0.86 mg 1^? total aluminium is fluoride bound aluminium, which means that appoximately 10% of total aluminium in tea infusion is complexed with fluoride.     

微波消解-氢化物发生-冷原子吸收光谱法测定茶叶中的镉

采用微波消解法对茶叶样品进行处理,使用改进的雾化装置,在室温下用原子吸收光谱法测定茶叶中的镉,对各种实验参数进行了优化,镉的检出限(K=3,n=11)为18ng.L-1,其相对标准偏差为3.5%,回收率在94.8%—104.2%之间。方法操作简单、实用、灵敏度高,适用于茶叶中镉的快速测定。     

基于共聚焦显微拉曼光谱揭示炭疽病侵染下茶叶细胞壁变化的研究

采用共聚焦显微拉曼技术研究了炭疽病感染所致茶叶细胞壁结构和化学成分的变化。对茶叶健康和染病组织细胞进行微米级空间分辨率的显微拉曼光谱扫描,并结合透射电镜观察炭疽病侵染所致的细胞超微结构变化,结果显示染病前后细胞壁的拉曼光谱位移和强度都有明显的差异,表明炭疽病侵染导致细胞壁中化学成分发生了较大的变化。其中由纤维素,果胶,酯类化合物产生的拉曼峰强度都有明显下降,说明细胞壁中这些物质的含量在染病后减少了;而木质素拉曼散射引起的拉曼峰强度有所上升,说明木质素的含量在染病后有所增加。随后基于纤维素的拉曼指纹波数和显微空间结构信息实现了茶叶健康组织和染病组织细胞壁中纤维素的化学成像分析,结果显示炭疽病侵染不仅导致细胞壁中纤维素的含量大大减少,而且纤维素的有序结构被破坏。由此得出结论：在无需对样本进行染色或复杂的化学处理的情况下,共聚焦显微拉曼可以揭示由炭疽病侵染引起的茶叶细胞壁化学成分和结构的变化,本研究是共聚焦显微拉曼技术首次用于植物病理学中寄主-病原物互作机制的研究,将为深入研究寄主-病原物在细胞层面上的互作机制开辟蹊径。