径向基函数神经网络光度法同时测定苯酚、邻苯二酚、间苯二酚和对苯二酚

对吸收峰重叠严重的苯酚、邻苯二酚、间苯二酚和对苯二酚4组分体系进行研究,以径向基函数神经网络光度法建立校正模型,同时测定了水样中的苯酚、邻苯二酚、间苯二酚和对苯二酚的含量,回收率为95.7％～109.2％。     

二维凝聚体系中分子的取向分布函数性质

对二阶和四阶Legondre多项式构造的取向分布函数进行了仔细研究, 发现该函数适于描述二维凝聚体系中单轴取向分子的四种分布模式, 给出了这四种分布模式对应的序参数〈P_2〉,〈P_4〉的取值区域, 具体讨论了序参数〈P_2〉,〈P_4〉改变时, 分布图形的相应变化.     

ZIF‐8@SiO2 core–shell microsphere extraction coupled with liquid chromatography and triple quadrupole tandem mass spectrometry for the quantitative analysis of four plant growth regulators in navel oranges

Monodisperse silica spheres that comprised a rhombic‐dodecahedral zeolitic imidazolate framework core–shell microsphere were applied in the sample pretreatment of navel orange. A rapid and efficient liquid chromatography with triple quadrupole tandem mass spectrometry method was established for simultaneously quantifying four plant growth regulators, 6‐benzylaminopurin, indole‐3‐acetic acid, indolepropionic acid, 3‐indolebutyric acid, in navel oranges. A satisfactory result was obtained, i.e., the peak area of the four plant growth regulators against concentration was linear with good correlation coefficients of 0.99987–0.99991. Under optimized conditions, the limits of detection were 3.0–59.4 μg/L for the four plant growth regulators. This method was applied to the simultaneous analysis of the four plant growth regulators in commercial samples, and all the detections were confirmed by acquiring transitions for each pesticide in the samples.     

Determination of tricyclic antidepressants in human plasma using pipette tip solid-phase extraction and gas chromatography-mass spectrometry

A method for the simultaneous extraction of four tricyclic antidepressants from human plasma samples using pipette tip SPE with MonoTip C(18) tips is presented. Human plasma (0.1 mL) containing four tricyclic antidepressants (amitriptyline, amoxapine, imipramine, and trimipramine) and an internal standard (IS), protriptyline, was mixed with 0.4 mL of distilled water and 100 microL 1 M NaOH solution. After centrifugation of the mixture, the supernatant was extracted to the C(18) phase of the tip by 20 repeated aspirating/dispensing cycles using a manual micropipettor. The analytes retained in the tip were eluted with methanol by five repeated aspirating/dispensing cycles. Without evaporation and reconstitution, the eluate was directly injected into a gas chromatograph injector and detected by a mass spectrometer with SIM in the positive-ion electron impact mode. Recovery of the four antidepressants and IS spiked into human plasma was 80.2-92.1%. The regression equations for the four antidepressants showed excellent linearity in the range of 0.2-40 ng/0.1 mL. LODs and LOQs for the four drugs were 0.05-0.2 ng/0.1 mL and 0.2-0.5 ng/0.1 mL, respectively. Intra- and interday CVs for the four drugs in plasma were no greater than 9.5%.     

微波消解-液相色谱-原子荧光光谱联用(LC-AFS)法测定稻米样品中砷形态

建立了稻米中4种砷元素形态的液相色谱-原子荧光光谱联用法(LC-AFS),样品用0.15mol/L的硝酸溶液微波提取50min,提取液经离心分离后,采用Hamilton PRP-X100色谱柱,45mmol/L KH2PO4-5mmol/L Na2HPO4缓冲液为流动相,砷形态4个组分能够在7min内达到基线分离,且无需调pH。优化了氢化物发生条件,使用了更低浓度的载流和还原剂。方法学实验结果表明,各组分在2~10ng/mL范围内线性关系良好,相关系数为0.9988~0.9998,各组分的检出限分别为0.29 ng/mL、0.47 ng/mL、0.62 ng/mL和1.16 ng/mL;各组分峰面积的相对标准偏差均低于3.11%;加标回收率为85.3%～112.8%;对稻米标准物质的分析测定结果表明该方法定值准确。最后,与GB 5009.11-2014中使用的提取及测量条件进行对比,表明该方具备法快速、环保、高效的特点。     

Mathematical Tool from Corn Stover TGA to Determine Its Composition

Corn stover was treated by steam explosion process at four different temperatures. A fraction of the four exploded matters was extracted by water. The eight samples (four from steam explosion and four from water extraction of exploded matters) were analysed by wet chemical way to quantify the amount of cellulose, hemicellulose and lignin. Thermogravimetric analysis in air atmosphere was executed on the eight samples. A mathematical tool was developed, using TGA data, to determine the composition of corn stover in terms of cellulose, hemicellulose and lignin. It uses the biomass degradation temperature as multiple linear function of the cellulose, hemicellulose and lignin content of the biomass with interactive terms. The mathematical tool predicted cellulose, hemicellulose and lignin contents with average absolute errors of 1.69, 5.59 and 0.74?%, respectively, compared to the wet chemical method.     

四种荧光素酯的化学物理性质

在紫外线的照射下,荧光素酯能与生物体细胞作用发出鲜艳的黄绿色荧光,由于生物体细胞的生活力不同,细胞内水解酶的含量也不同,因而显出的荧光强度不同。借此性质可以测定细胞内荧光素水解酶的活性以及细胞的生活状态。由于它们是一类选择性好,灵敏度较高的生物荧光染色剂,所以深入研究四种荧光素酯的化学物理性质是有意义的。四种荧光素酯的分子结构可用下面通式表示。     

Tetrathiafulvalene-functionalized Cavitands as Building Blocks for Redox Active Hemicarcerands

Two new cavitands bearing four upper-rim tetrathiafulvalene (TTF) units were synthesized. One of these cavitands was used to prepare a redox-active hemicarcerand containing four TTF subunits covalently appended to its equatorial region. Preliminary electrochemical characterization data show that the four TTF residues in all these compounds behave as independent, non-interacting groups in their heterogeneous electron transfer reactions.     

Analysis of lipoproteins using 2D diffusion-edited NMR spectroscopy and multi-way chemometrics

This study represents the first application of multi-way calibration by N-PLS and multi-way curve resolution by PARAFAC to 2D diffusion-edited ¹H NMR spectra. The aim of the analysis was to evaluate the potential for quantification of lipoprotein main- and subfractions in human plasma samples. Multi-way N-PLS calibrations relating the methyl and methylene peaks of lipoprotein lipids to concentrations of the four main lipoprotein fractions as well as 11 subfractions were developed with high correlations (R = 0.75-0.98). Furthermore, a PARAFAC model with four chemically meaningful components was calculated from the 2D diffusion-edited spectra of the methylene peak of lipids. Although the four extracted PARAFAC components represent molecules of sizes that correspond to the four main fractions of lipoproteins, the corresponding concentrations of the four PARAFAC components proved not to be correlated to the reference concentrations of these four fractions in the plasma samples as determined by ultracentrifugation. These results indicate that NMR provides complementary information on the classification of lipoprotein fractions compared to ultracentrifugation.     

Simple and Sensitive Determination of Aromatic Acids in Coconut Water by g-C3N4@SiO2Based Solid-phase Extraction and HPLC-UV Analysis

In this study, graphitic carbon nitride deposited silica(g-C₃N₄@SiO₂) was prepared by simple pyrolysis of melamine on silica and then used as a solid-phase extraction(SPE) sorbent for the extraction of four representative aromatic acids including benzoic acid(BA), salicylic acid(SA), indolyl-3-butyricacid(IBA) and naphthalene acetic acid(NAA) in coconut water(CW) samples. g-C₃N₄@SiO₂ exhibited an excellent adsorption capacity for the four aromatic acids, which are in the concentration range of 500-558.8 μg/g. The four aromatic acids could be directly captured by g-C₃N₄@SiO₂ from CW samples within 5 min. Thus, a rapid, simple and effective method for the analysis of four aromatic acids in CW samples was developed by coupling g-C₃N₄@SiO₂-based SPE with high performance liquid chromatography-ultraviolet(HPLC-UV) detection. The linearity of the developed method was in the range of 20-1000 ng/mL and its limit of detection was in the range of 1.9-5.7 ng/mL, which were signi-ficantly lower than those of the reported similar methods. The intra-day and inter-day precisions(based on the relative standard deviation, n=3) of the four aromatic acids were under 9.5% and 10.4%, respectively. The developed method was applied to determining the four aromatic acids in real CW samples and the spiked recoveries varied from 81.1% to 121.8%.     

An expeditious total synthesis of (+/-)-stenine

(+/-)-Stenine was synthesized in eight steps from a known ketophosphonate reagent. The key step was an exo-selective Diels-Alder/intramolecular Schmidt domino reaction that afforded three of the four rings and four stereocenters in a single reaction.     

Determination of fluoroquinolones in blood by matrix solid-phase dispersion extraction and CE

A simple and rapid method for the determination of residues of four fluoroquinolones in blood samples was developed. The method was based on matrix solid‐phase dispersion extraction followed by CE with ultraviolet detection. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate aqueous solution was used as the background electrolyte for the separation of fluoroquinolones. The average recoveries of the four fluoroquinolones at two spiked levels ranged from 54.0 to 86.4% for pig blood, and 45.4 to 79.9% for deer blood, with the relative standard deviations <9.45%. Detection limits for the four fluoroquinolones in blood sample ranged from 0.15 to 0.31 μg/mL.     

Investigating the morphology and mechanical properties of blastomeres with atomic force microscopy

Atomic force microscopy (AFM) was used to directly investigate the morphology and mechanical properties of blastomeres during the embryo development. With AFM imaging, the surface topography of blastomeres from two‐cell, four‐cell, and eight‐cell stages was visualized, and the AFM images clearly revealed the blastomere's morphological changes during the different embryo developmental stages. The section measurements of the AFM topography images of the blastomeres showed that the axis of the embryos nearly kept constant during the two‐cell, four‐cell, and eight‐cell stages. With AFM indenting, the mechanical properties of living blastomeres from several embryos were measured quantitatively under physiological conditions. The results of mechanical properties measurements indicated that the Young's modulus of the two blastomeres from two‐cell embryo was different from each other, and the four blastomeres from the four‐cell embryo also had variable Young's modulus. Besides, the blastomeres from two‐cell embryos were significantly harder than blastomeres from four‐cell embryos. These results can improve our understanding of the embryo development from the view of cell mechanics. Copyright © 2013 John Wiley & Sons, Ltd.     

A unique tetramer of 4:5 beta-cyclodextrin-ferrocene in the solid state

A single crystal of a unique 4:5 inclusion complex between beta-cyclodextrin and ferrocene was prepared and the structure was determined by X-ray crystallographic analysis, showing that four of the five ferrocenes were included in the cavities of four beta-cyclodextrins along the axial orientation of the tetramer, while another was co-included between two beta-cyclodextrins from the equatorial orientation.     

HPLC determination of safflor yellow A and three active isoflavones from TCM Naodesheng in rat plasma and tissues and its application to pharmacokinetic studies

A high-performance liquid chromatographic method was developed for the simultaneous determination and pharmacokinetic studies of safflor yellow A, puerarin, 3'-methoxyl-puerarin, and puerarinapioside in the plasma and tissues of rats that had been administered with the traditional Chinese medicine (TCM) preparation Naodesheng via the caudal vein. Samples taken from rats were subjected to protein precipitation with acetone. Separation of these four compounds was accomplished on a Kromisil C18 stationary phase using a mobile phase of acetonitrile-0.1% phosphoric acid-tetrahydrofuran (8:92:2, v/v/v) at a flow-rate of 1.0 mL/min. The detection wavelength was set at 250 nm. The calibration curves of the four components were linear in the given concentration ranges. The intra- and inter-day precisions in plasma and tissues were less than 15% and the extraction recoveries were higher than 60%. The lower limits of quantitation of four components were low enough to determine the four components. These four components all exhibited kinetics that fitted a two-compartment model in rats. The elimination half-life was 1.19 h for safflor yellow A, 2.69 h for puerarin, 2.94 h for 3'-methoxyl-puerarin, and 0.87 h for puerarinapioside, respectively. Following administration of a single injection of Naodesheng, the concentration (C) of the four components in the tissues showed C(kidney) > C(lung), C(liver) > C(spleen), C(stomach), C(heart), approximately. The method is a reliable tool for performing studies of safflor yellow A and three puerarin isoflavones in different biological material.     

Kinetics of adsorption of di-n-butyl phthalate (DBP) by four different granule-activated carbons

The kinetics of the adsorption of an endocrine disruptor, di-n-butyl phthalate (DBP), by four different granulated-activated carbons (GACs) is presented in this paper. Results showed that adsorption of DBP by the four GACs followed first-order kinetics and the adsorption constant of the four GAC was found to follow the order: nut shell>coconut shell>Coaly carbon 1.0>Coaly carbon 1.5. Batch adsorption studies were also conducted to investigate the effect of pH on the adsorption process. The optimum pH for the removal of DBP from aqueous solutions under the experimental conditions used in this work was found to be 5.0. The characterization of the carbon surfaces was conducted by using scanning electron microscopy (SEM). Furthermore, results from infrared spectroscopic (IR) studies showed that physical adsorption plays an important role in the adsorption of DBP by the four selected GACs.     

Improved method for analyzing estrogens in water by liquid chromatography-electrospray mass spectrometry

An improved LC-electrospray ionization MS method was established for four estrogens (17beta-estradiol (E2), estriol (E3), estrone (E1), and ethynyl estradiol (EE)) in environmental water. Almost complete separation of all estrogens was achieved on a phenyl column with methanol/water as the mobile phase. Quantification was achieved in the negative ionization mode using selected ion monitoring. The instrumental detection limits were 20-30 ng/l for the four analytes. In Milli-Q spiked water, the recoveries of the four estrogens were 72-81%, which was similar to those found for river water spiked with the corresponding deuterated estrogens. The detection limits for the four estrogens in river water were 0.1-0.2 ng/l. The method was used to detect residual estrogens in the Tonghui River, which receives water from a municipal sewage treatment plant in Beijing; E1 (1.1 ng/l) and E2 (0.2 ng/l) were detected.     

A New Method of Separation of Four Benzodiazepines by RP-CEC

A new method to separate diazepam, nitrazepam, estazolam, alprazolam was established on both C18 and C8 CEC columns. The influence of separation voltage, Tris concentration, column temperature and the percentage of acetonitrile on the resolution and retention behavior of four benzodiazepines was investigated. The results showed that the percentage of acetonitrile had the largest effect on the resolution and retention behavior of the four benzodiazepines. Other separation conditions had also effects on the resolution and retention behavior, but smaller than the concentration of acetonitrile. Optimum separation conditions were obtained to separate four benzodiazepines on C18 and C8 CEC columns.     

Microchip-based immunoassay system with branching multichannels for simultaneous determination of interferon-gamma

A bead-bed immunoassay system suitable for simultaneous assay of multiple samples was constructed on a microchip. The chip had branching multichannels and four reaction and detection regions; the constructed system could process four samples at a time with only one pump unit. Interferon gamma was assayed by a 3-step sandwich immunoassay with the system coupled to a thermal lens microscope as a detector. The biases of the signal intensities obtained from each channel were within 10%, and coefficients of variation were almost the same level as the single straight channel assay. The assay time for four samples was 50 min instead of 35 min for one sample in the single-channel assay; hence higher throughput was realized with the branching structure chip.