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.     

Determination of ethylene glycol dinitrate in dynamites using HPLC: application to the plastic explosive Goma-2 ECO

In this study, a sequential extraction method using water and methanol to recover ethylene glycol dinitrate or nitroglycol (EGDN) contained in Goma-2 ECO dynamite was developed. After, an HPLC method was used for the determination of EGDN in the two extracted phases. The analytical method was validated by evaluating its selectivity, sensitivity, linearity, and linear working concentration range, limit of detection and quantitation, precision (as repeatability and intermediate precision), accuracy, and robustness, providing appropriate values (i.e. RSD values for precision about 6% and accuracy about 100%). Finally, the EGDN content of a sample of the Goma-2-ECO dynamite was determined obtaining a concentration of 30.29%, which is in accordance with the manufacturer's specifications for this dynamite (25.7-31.4%).     

Extraction tool and matrix effects on arsenic speciation analysis in cell lines

Arsenic glutathione (As–GSH) complexes have been suggested as possible metabolites in arsenic (As) metabolism. Extensive research has been performed on the toxicological and apoptotic effects of As, while few reports exist on its metabolism at the cellular level due to the analytical challenges. In this study, an efficient extraction method for arsenicals from cell lines was developed. Evaluation of extraction tools; vortex, ultrasonic bath and ultrasonic probe and solvents; water, chemicals (methanol and trifluoroacetic acid), and enzymes (pepsin, trypsin and protease) was performed. GSH effect on the stability of As–GSH complexes was studied. Arsenic metabolites in dimethylarsino glutathione (DMA(GS)) incubated multiple myeloma cell lines were identified following extraction. Intracellular GSH concentrations of myeloma cell lines were imitated in the extraction media and its corresponding effect on the stability and distribution of As metabolites was studied. An enhancement in both extraction recoveries and time efficiency with the use of the ultrasonic probe was observed. Higher stabilities for the As species in water, pepsin and trypsin were obtained. The presence of 0.5 mM GSH in the extraction media (PBS, pH 7.4) could not stabilize the As–GSH complexes compared to the 5 mM GSH, where high stabilization of the complexes was observed over a 5 day storage study. Finally, the speciation analysis of the DMA(GS) culture incubated cell lines in the presence or absence of GSH revealed the important role GSH plays in the preservation of DMA(GS) identity. Hence, caution is required during the extraction of arsenicals especially the As–GSH complexes, since their identification is highly dependent on GSH concentration.     

Influence of extraction methods on stability of flavonoids

The LC-MS/MS was applied for the determination of flavonoids' stability under four types of solvent extraction methods (reflux heating, sonication, maceration and microwave) from maize samples. The 11 flavonoids belong to different groups: flavonols (kaempferol, myricetin, rhamnetin, quercetin, rutin), flavanones (naringenin, naringin, hesperedin), flavones (apigenin, luteolin), isoflavones (genistein) were studied. The effect of the degradation of flavonoids depended on extraction mode and chemical structure. The smallest decomposition was observed by heated reflux extraction procedure within 30 min in water bath and by microwave assisted extraction under 160 W during 1 min. The decomposition for flavonoids depends on number of substituents in flavonoid molecule. The most unstable compound (recovery below 50%) in tested condition was myricetin. The higher number of hydroxyl groups promote degradation of flavonoids, whereas sugar moiety and methoxyl groups protect flavonoids of degradation during microwave and ultrasonic assisted extraction.     

Reversed phase partition chromatographic separation of divalent copper with N-n-octylaniline on silica gel

A novel separation method was developed for the extraction and chromatographic separation of copper(II). The quantative extraction of 25.0–125.0 μg copper(II) has been observed from 0.05 to 0.25 mol/L of ascorbic acid at pH 9.0–12.0 with 0.087 mol/L N-n-octylaniline (liquid anion exchanger) coated on silica gel at a flow rate of 1.0 ml/min. The extracted metal ion has been recovered by eluting with 25.0 ml of 1.0 mol/L hydrochloric acid and determined spectrophotometrically by rubeanic acid method. The various influencing parameters viz. acid concentrations, reagent concentration, eluates effect of pH, and effect of flow rate on extraction were studied. The method is free from large number of interferences from cations and anions. A scheme for mutual separation of copper(II), gold(III) and bismuth(III) has been developed. Copper(II) has been separated from ayurvedic (Herbal) medicine and synthetic mixtures corresponding to alloy. The log–log plot of N-n-octylaniline concentration versus the distribution coefficient indicates that the probable extracted species is [.     

Mechanistic pathway for controlled extraction of guest molecule bound to herring sperm DNA using α-cyclodextrin

trans-2-[4-(Dimethylamino)styryl]benzothiazole (DMASBT) is known to have dual emitting states where the locally excited (LE) state is responsible for fluorescence in less polar environment and in polar milieu fluorescence is from the twisted intramolecular charge transfer (TICT) state. This compound also undergoes minor groove binding to herring sperm DNA (hsDNA) evidenced by the absorption spectra before and after the binding process and an effect on DMASBT fluorescence by an anionic quencher. The binding occurs efficiently in a 1:1 manner, i.e. one guest molecule binds to one site on the hsDNA. Instead of following the DNA twist, the aromatic part seems to project outward. Thus, the bound molecule can be successfully extracted out from the DNA in a controlled way by the hydrophobic cavity of α-cyclodextrin (α-CD). The extraction starts even with a low concentration of α-CD and increases as the concentration is increased. Absorption, steady-state and time resolved fluorescence spectroscopic methods have been employed to explore the mechanistic pathway of binding of DMASBT to hsDNA. The mechanistic approach toward controlled extraction of the guest molecules from hsDNA by α-CD is reported and is expected to serve a significant purpose in treatment of drug overdose.     

Separation of nitrophenols. Equilibriums in bi- and tri-phasic systems

The paper presents experimental data obtained in the study of liquid–liquid partition equilibriums in biphasic system in order to optimize the process of transport through bulk liquid membranes (triphasic partition systems). The partition equilibriums of some nitrophenols using chloroform as extraction solvent and membranary solvent, respectively, were studied. The influence of the pH on the partition equilibriums was investigated. The repartition constants and the pK_a values of the studied nitrophenols were calculated. Nitrophenols were transferred in triphasic system from a feed phase with pH 2, through a chloroform liquid membrane, into a receiving phase with pH 12, with efficiencies over 90%.     

基于DEMON线谱的轴频提取方法研究

目标的螺旋桨不同则轴频不相同。轴频是目标的特征之一,可以应用于目标识别当中。本文提出一种改进的高频噪声解调分析(DEMON)方法,能够得到具有明显线谱的DEMON谱;提出最大公约数算法,并给出提取轴频的具体步骤。海试数据实验结果验证了本文所提方法及算法的有效性和可行性。     

碘-四氯化碳萃取光度法间接测定食品中的痕量过氧化氢

在 p H1.0— 3.0稀硫酸介质中 ,一定的反应条件下 ,过氧化氢与碘化钾反应 ,释放出一定量的碘 ,建立了碘 -四氯化碳萃取光度法间接测定痕量过氧化氢。共存离子基本上不干扰测定 ,过氧化氢的检测限为0 .0 5 μg·m L-1;回收率在 94 %— 98%之间 ,结果令人满意