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41.
甲基绿褪色分光光度法测定维生素K3 总被引:1,自引:0,他引:1
在pH8.7~9.5的弱碱性介质中,维生素K3(VK3)能使甲基绿发生褪色反应,其最大褪色波长为630nm,并在紫外区出现两个新的吸收峰,其褪色程度(ΔA)与VK3浓度在0·11~2·40mg/L的范围呈正比,可用于VK3的分光光度测定。方法具有很高的灵敏度,其表观摩尔吸光系数ε630=2·13×105L·mol-1·cm-1;对VK3的检出限(3σ)为32·0μg/L。方法有较好的选择性,可用于某些药物制剂及血药中VK3含量的测定。 相似文献
42.
BaoAnSONG GangLIU DeYuHU HuaZHANG 《中国化学快报》2004,15(10):1140-1142
A series of substituted (6-chloropyridine-3-yl)methyl heterocyclic thioether derivatives were prepared by indium mediating in water. The preliminary biological tests showed that compound 3d exhibited good antiviral activity. 相似文献
43.
高效液相钴离子催化化学发光抑制法测定茶叶中的茶氨酸 总被引:5,自引:0,他引:5
研究了用高效液相分离、抑制化学发光测定茶叶中茶氨酸的分析方法。该法采用YWG C18(10μm,250mm×5 0mmi d )柱,以0 01mol·L-1醋酸钠 醋酸缓冲液(pH5 5)为流动相,流速为0 8mL·min-1。对茶氨酸抑制Co2+催化鲁米诺(luminol)与过氧化氢(H2O2)化学发光反应的条件进行了优化:Co2+的质量浓度为2μg·L-1,鲁米诺浓度为0 25mmol·L-1,H2O2浓度为0 5mmol·L-1。在茶氨酸的质量浓度为0 2g·L-1~5 0g·L-1时,茶氨酸抑制化学发光产生负峰的相对峰面积Y(将实际峰面积缩小至万分之一)与其质量浓度X(kg·L-1)的线性回归方程为Y=33862X+1 0605(r=0 9983)。 相似文献
44.
Synthesis and Crystal Structure of N-Hydroxy-9-(3’,4’-methylene- dioxyphenyl)-1,8-dioxo-1,2,3,4,5,6,7,8,9, 10-decahydroacridine in Aqueous Media 总被引:1,自引:0,他引:1
1 INTRODUCTION Acridine derivatives are described to have many applications, such as biological fluorescent probes[1] as well as anti-tumor[2], anti-bacterial[3], anti-HIV[4] and anti-malarial[5] agents. Because of the importance of acridine derivatives, much work has been done for several decades. Among them the classical synthetic methods involve condensing functionalized anilines and o-halogeno- benzoic acid derivatives as well as several other steps resulting in the desired acridine[… 相似文献
45.
46.
Feasibility study for the use of near infrared spectroscopy in the qualitative and quantitative analysis of green tea, Camellia sinensis (L.) 总被引:1,自引:0,他引:1
J. Luypaert 《Analytica chimica acta》2003,478(2):303-312
This paper indicates the possibility to use near infrared spectroscopy (NIR) combined with PLS as a rapid method to estimate the quality of green tea. NIR is used to build calibration models to predict the content of caffeine, epigallocatechin gallate (EGCG) and epicatechin (EC) and for the prediction of the total antioxidant capacity of green tea. For the determination of the total antioxidant capacity, the trolox equivalent antioxidant capacity (TEAC) method is used. Until now, the prediction of the antioxidant capacity as such by use of NIR has not been reported. For caffeine and TEAC, models are build for the whole green tea leaves and also for the ground leaves. For the polyphenols (EGCG and EC), only models for the whole leaves are investigated. A partial least squares (PLS) algorithm is used to perform the calibration. To decide upon the number of PLS factors included in the PLS model, the model with the lowest root mean square error of cross-validation (RMSECV) for the training set is chosen. The correlation coefficient (r) between the predicted and the reference results for the test set is used as an evaluation parameter for the models: for the TEAC results r=0.90 for the model with the whole leaves, r=0.86 for the model with the powdered leaves are obtained. The caffeine prediction model has a correlation coefficient r=0.96 for the whole leaves and r=0.93 for the ground leaves. The correlation coefficient for the EGCG and the EC content models are, respectively 0.83 and 0.44. 相似文献
47.
A multi-residue cation-exchange clean up procedure for basic drugs in produce of animal origin 总被引:1,自引:0,他引:1
George Stubbings Jonathan Tarbin Andrew Cooper Matthew Sharman Tim Bigwood Paul Robb 《Analytica chimica acta》2005,547(2):262-268
There is considerable interest in maximising the amount of information obtained from animal product analyses, when screening for the presence of veterinary drug residues. One of the barriers to effective multi-residue analysis to date has been a lack of effective clean up procedures to isolate a wide range of residues from the potential interferents, which may be present in both simple and complex (including processed) foods. A cation-exchange clean up has, therefore, been developed for use with acetonitrile extracts of foods, when analysing for several basic drug groups (sulfonamides, benzimidazoles, levamisole, nitroimidazoles, tranquillisers and fluroquinolones). The clean up procedure has also been shown to be effective using a modified extraction solvent for malachite green and leucomalachite green in fish.Several of the key parameters that influence analyte recovery have been investigated and in an optimised procedure, tissue/biofluid samples containing sulfonamides, benzimidazoles, levamisole, nitroimidazoles, tranquillisers and fluoroquinolones are first extracted with acetonitrile. The extract is then dried with sodium sulfate and acidified with glacial acetic acid before loading onto a Bond Elut, strong cation-exchange (SCX) solid phase extraction (SPE) cartridge. Extracts from fish containing malachite green and leucomalachite green can be cleaned up using the same SCX SPE procedure following extraction with citrate buffer/acetonitrile. Typical recoveries of drugs from low level fortified tissues using the optimised procedure lie in the range 53-104% with the exception of carazolol from pig kidney (31%), malachite green from trout (42-51%) and ciprofloxacin from chicken muscle (44%) and from egg (21%). 相似文献
48.
Thereza Christina Vessoni Penna Eb Chiarini Adalberto Pessoa Junior 《Applied biochemistry and biotechnology》2003,107(1-3):481-491
Transformed cells of Escherichia coli expressing recombinant green fluorescent protein (GFPuv) were subjected to two methods of extraction: (1) freezing/thawing/sonication
(FTS) cycles prior to the three-phase partitioning (TPP) method, or (2) directly to TPP extraction. The amount of GFPuv released
by the FTS plus TPP method varied: 374μg/mL (first cycle), 93–442 μg/mL (second cycle), 32–359 μg/mL (third cycle), 18–115
μg/mL (fourth cycle). The GFPuv yields by the second method (TPP only) were, 23–54 μg/mL for the first extract and 33–91 μg/mL
for the second. The FTS plus TPP method released similar amounts of GFPuv to that extracted by TPP; and provided a better
mixture elution through the hydrophobic interaction column: 13–63 μg/mL for FTS plus TPP methods, and 2.5–13 μg/mL for TPP.
The results showed that although selective permeation is a more laborious methodology, it was more efficient for obtaining
of GFPuv in relation to the direct extraction of the cells for TPP. 相似文献
49.
Synthesis and properties of chiral ammonium-based ionic liquids 总被引:1,自引:0,他引:1
New chiral ammonium-based ionic liquids containing the (1R,2S,5R)-(-)-menthyl group can be easily and efficiently prepared under ambient conditions. The preparation and characterization of trialkyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium salts is reported. The salts have been demonstrated to be air- and moisture-stable under ambient conditions and can be readily used in a variety of standard experimental procedures. The single-crystal X-ray structure of butyldimethyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium chloride has been determined. The chiral, room-temperature ionic liquids have been characterized by physical properties such as specific rotation, density, viscosity, thermal degradation, and glass transition temperature. Trialkyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium chloride prototype ionic liquids have also been found to exhibit strong antimicrobial and high antielectrostatic activities. 相似文献
50.
《Chemphyschem》2003,4(6):588-594
The reorientational dynamics of the ionic liquid 1butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM]PF6) were studied over a wide range of temperatures by measurement of 13C spin–lattice relaxation rates and NOE factors. The reorientational dynamics were evaluated by performing fits to the experimental relaxation data. Thus, the overall reorientational motion was described by a Cole–Davidson spectral density with a Vogel–Fulcher–Tammann temperature dependence of the correlation times. The reorientational motion of the butyl chain was modelled by a combination of the latter model for the overall motion with a Bloembergen–Purcell–Pound spectral density and an Arrhenius temperature dependence for the internal motion. Except for C2 in the aromatic ring, an additional reduction of the spectral density by the Lipari–Szabo model had to be employed. This reduction is a consequence of fast molecular motions before the rotational diffusion process becomes effective. The C2 atom did not exhibit this reduction, because the librational motion of the corresponding C2? H vector is severely hindered due to hydrogen bonding with the hexafluorophosphate anion. The observed dynamic features of the [BMIM]+ cation confirm quantum‐chemical structures obtained in a former study. 相似文献