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Summary

A high-performance liquid chromatographic (HPLC) technique coupled with photodiode array (PDA) detection has been proposed for simultaneous determination of five flavonoids, i.e. quercetin 3-O-β-d-glucopyranoside, quercetin 4′-methoxy-3-O-β-d-galactopyranoside, kaempferol 3-O-β-l-rhamnopyranoside, asebotin, and kaempferol 7-methxoy-3-O-α-l-rhamnopyranoside in extract of the whole plant of Saussurea mongolica Franch. The optimum conditions for separation were achieved on a 4.6 × 250 mm i.d., 5-μm particle, C18 column with acetonitrile and 1% acetic acid (20:80, v/v) as the mobile phase at a flow rate of 1.0 mL min−1. For all the analytes, a good linear regression relationship (r of >0.999) was obtained between peak area and concentration over a relatively wide range. The method was validated for repeatability, precision, stability, and accuracy. Seven different extraction procedures were investigated for preparation of the sample solution. The validated method was successfully applied to simultaneous analysis of these flavonoids in S. mongolica and was found to be simple and efficient.

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A new method using ultra-performance liquid chromatography (UPLC) in combination with tandem mass spectrometry and a multiple reaction monitoring mode (UPLC-MS/MS-MRM) was developed for simultaneous quantitative determination of anthraquinone derivatives in Radix et Rhizoma Rhei-based medicines. A multi-mode electrospray/chemical ionization (ESCI) and negative ion mode with [M-H] and its fragments under collision-activated conditions were employed in MS/MS-MRM. The quantitative method was validated and applied to simultaneous determination of anthraquinone derivatives in 21 Radix et Rhizoma Rhei-based medicines. The limits of quantification were in the range of 3.90–9.09 ng mL−1. Average recoveries were between 95.5% and 99.8% with relative standard deviations from 1.8% to 5.3%.

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Summary

A novel liquid-phase microextraction (LPME) technique, based on a hollow fiber (HF), in conjunction with high-performance liquid chromatography, has been developed for analysis of melamine in milk products. Melamine was extracted directly from milk products by use of a hollow-fiber membrane filled with organic solvent. HFLPME conditions, for example pH, extraction solvent, temperature, stirring rate, and extraction time were optimized. The best extraction efficiency of melamine was achieved under the conditions: pH 9.5, 35 μL n-octanol as extraction solvent, temperature 55°C, stirring rate 300 rpm, and extraction time 30 min. The HF-LPME technique resulted in a preconcentration ratio of 29-fold. Baseline chromatographic separation of melamine was achieved on a C18 column with 96:4 (v/v) 0.02 mol L−1 ammonium sulfate-methanol as isocratic mobile phase. The linearity of the method ranged from 1.0 to 100.0 μg mL−1, correlation coefficient 0.9994. The limit of detection by use of HF-LPME was 0.021 μg mL−1 at a signal-to-noise ratio of 3. The optimized HF-LPME technique was successfully applied to the analysis of melamine in milk products collected from different commodity manufacturing units.

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Summary

A high-performance liquid chromatographic (HPLC) method coupled with photodiode array (PDA) detection has been developed and validated for simultaneous analysis of six active components (syringin, hyperoside, baicalin, quercetin, baicalein, and farrerol) of the Chinese medicinal preparation Qin-Bao-Hong antitussive tablet. The optimum conditions for separation were achieved on a 3.9 mm × 150 mm i.d., 5-μm particle, C18 column with a linear mobile phase gradient prepared from acetonitrile and 1% acetic acid at a flow rate of 1.0 mL min−1. Because of the different UV characteristics of these compounds, four detection wavelengths were used for the quantitative analysis (265 nm for syringin, 256 nm for hyperoside and quercetin, 277 nm for baicalin and baicalein, and 296 nm for farrerol). For all the analytes a good linear regression relationship (r > 0.999) was obtained between peak area and concentration over a relatively wide range. The method was validated for repeatability, precision, stability, accuracy, selectivity, and robustness. The validated method was successfully applied to simultaneous analysis of these active components in Qin-Bao-Hong antitussive tablet from different production batches.

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Summary

A high-performance liquid chromatography (HPLC) method has been developed for simultaneous determination of six alkaloids, i.e., (−)-(R)-platydesmin, noroxyhydrastinine, berberine, skimmianine, canthin-6-one, and pteleine in the herbal medicine of Phellodendron amurense Rupr. The optimal condition for extraction and separation was achieved with a linear mobile phase gradient prepared from 0.1% phosphoric acid and acetonitrile. The LODs and LOQs for the analytes ranged from 0.06 to 0.22 μg mL−1 and from 0.25 to 0.80 μg mL−1, respectively. The optimized method was applied to the determination of alkaloids in P. amurense Rupr. and was found to be efficient. This method can provide a scientific and technical platform to the manufacturers for setting up a quality control standard as well as to the public for quality and safety assurance of the proprietary traditional Chinese medicines.

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Thermodynamic investigation of several natural polyols (II)

Heat capacities and thermodynamic properties of sorbitol

Journal of Thermal Analysis and Calorimetry
Authors: B. Tong, Z. Tan, Q. Shi, Y. Li, and S. Wang

Abstract  

The low-temperature heat capacity C p,m of sorbitol was precisely measured in the temperature range from 80 to 390 K by means of a small sample automated adiabatic calorimeter. A solid-liquid phase transition was found at T=369.157 K from the experimental C p-T curve. The dependence of heat capacity on the temperature was fitted to the following polynomial equations with least square method. In the temperature range of 80 to 355 K, C p,m/J K−1 mol−1=170.17+157.75x+128.03x 2-146.44x 3-335.66x 4+177.71x 5+306.15x 6, x= [(T/K)−217.5]/137.5. In the temperature range of 375 to 390 K, C p,m/J K−1 mol−1=518.13+3.2819x, x=[(T/K)-382.5]/7.5. The molar enthalpy and entropy of this transition were determined to be 30.35±0.15 kJ mol−1 and 82.22±0.41 J K−1 mol−1 respectively. The thermodynamic functions [H T-H 298.15] and [S T-S 298.15], were derived from the heat capacity data in the temperature range of 80 to 390 K with an interval of 5 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement with those obtained from heat capacity measurements.

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Abstract  

The effect of glucose (0–15 mass%) on the kinetics of bovine serum albumin (BSA) denatured aggregation at high concentration in aqueous solution has been studied by differential scanning calorimetry. The observed denatured aggregation process was irreversible and could be characterized by a denaturation temperature (T m), apparent activation energy (E a), the approximate order of reaction, and pre-exponential factor (A). As the glucose concentration increased from 0 to 15 mass%, T m increased, E a also increased from 514.59409±6.61489 to 548.48611±7.81302 kJ mol−1, and A/s−1 increased from 1.24239E79 to 5.59975E83. The stabilization increased with an increasing concentration of glucose, which was attributed to its ability to alter protein denatured aggregation kinetics. The kinetic analysis was carried out using a composite procedure involving the iso-conversional method and the master plots method. The iso-conversional method indicated that denatured aggregation of BSA in the presence and absence of glucose should conform to single reaction model. The master plots method suggested that the simple order reaction model best describe the process. This study shows the combination of iso-conversional method and the master plots method can be used to quantitatively model the denatured aggregation mechanism of the BSA in the presence and absence of glucose.

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Summary

A simple and rapid method, using online ultraperformance liquid chromatography with photodiode array detection and electrospray ionization mass spectrometry (UPLC-PDA-eλ-ESI-MS/MS), was developed for the in-depth analysis of 50 batches Radix et Rhizoma Rhei. The analysis was performed on a UPLC BEH C18 column using a gradient elution system. Baseline separation could be achieved in less than 7.5 min. At the same time, on the basis of the 50 batches of samples collected from representative cultivated regions, a novel chromatographic fingerprint was devised by UPLC-PDA, in which 27 common peaks were detected and identified by the developed UPLC-MS/MS method step by step according to fragmentation mechanisms, MS/MS data, standards, and relevant literature. Many active components gave prominent [M - H] ions in the ESI mass spectra. These components include anthraquinones, sennosides, stilbenes, glucose gallates, naphthalenes, and catechins. Furthermore, based on the information of these Radix et Rhizoma Rhei components, and further combined with discriminant analysis, a novel discriminant analysis equation (DAE) was established for the quality control of Radix et Rhizoma Rhei for the first time.

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Fluid radiation effects in the transient hot-wire technique

Measurement of thermal conductivity of propane

Journal of Thermal Analysis and Calorimetry
Authors: Y. Shi, L. Sun, F. Tian, J. Venart, and R. Prasad

Abstract  

The transient hot-wire technique is widely used for absolute measurements of the thermal conductivity of fluids. Refinement of this method has resulted in a capability for accurate and simultaneous measurement of both thermal conductivity and thermal diffusivity together with a determination of the specific heat. However, these measurements, especially those for the thermal diffusivity, may be significantly influenced by fluid radiation. The present work investigates the effect of fluid radiation on the measurements of the thermal conductivity of propane. Recently developed corrections have been used to examine this assumption and rectify the influence of even weak fluid radiation. Measurements at 372 K with a hot-wire instrument demonstrate the presence of radiation effects in both the liquid and vapor phase. The influence is much more pronounced in liquid propane at 15.5 MPa than in the vapor phase at 881.5 kPa. The technique employed to obtain radiation-free thermal conductivity measurements is described.

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