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.
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.
Authors:Y. Q. Cheng, Y. X. Zhang, S. D. Qi, H. L. Chen, and X. G. Chen
1,7-Dihydroxy-3,8-dimethoxyxanthone (X1) and 1,8-dihydroxy-3,7-dimethoxyxanthone (X2) are two important xanthones of the Tibetan medicinal plant Gentianopsis paludosa (Hook. f.) Ma. They are very similar in structure, the only difference being exchange of OH and OCH3 at the 7 and 8 positions. By calculations based on the geometry of the molecules using the MM+ force field, the different distances between the hydroxyl groups of the two xanthones were obtained (4.64774 Å for X2 and 7.19412 Å for X1), therefore, the two hydroxyl groups of X1 should freely interact with more water molecules than those of X2 in aqueous solution. In other words, X2 is more hydrophobic than X1. Micellar electrokinetic capillary chromatography (MEKC) was therefore chosen for separation of the compounds. The optimum separation conditions were: 20 mm borate + 20 mm SDS (pH 9.8) as running buffer, 17.5 kV applied potential, and detection wavelength 260 nm. The two xanthones were well separated in 9.0 min, with Gaussian peak shapes. The repeatability of the MEKC method (expressed as RSD) for X1 and X2 was 0.9 and 1.1%, respectively, for migration time, and 3.1 and 1.4% for peak area. The limits of detection (S/N = 3) were 0.41 μg mL−1 for X1 and 0.82 μg mL−1 for X2. The recovery of the MEKC method for the two xanthones was also satisfactory.
A novel complex, [Pr(5-nip)(phen)(NO3)(DMF)]
(5-nip: 5-nitroisophthalic acid; phen: 1,10-phenanthroline, DMF: N,N-dimethylformamide),
was prepared and characterized by single crystal X-ray diffraction, elemental
analysis, IR spectrum and DTG-DSC techniques. The results show that the crystal
is monoclinic, space group P2(1)/n with a=11.0876(6) Å, b=12.8739(7)
Å, c=16.9994(8) Å; β=91.193(4)°, Z=4, Dc=1.822
Mg m–3, F(000)=1320.
Each Pr(III) ion is nine-coordinated by one chelating bidentate and two monodentate
bridging carboxylate groups, one chelating bidentate nitryl group, one DMF
molecule and one 1,10-phenanthroline molecule. The complex is constructed
with one-dimensional ribbons featuring dinuclear units and the one-dimensional
ribbons are further assembled into two-dimensional networks by strong π–π
stacking interactions. The complex has high stability up to 500°C. The
enthalpy change of formation of the compound in DMF was measured using an
RD496-III type microcalorimeter with the value of –9.214±0.173
Chlorophyll content is positively correlated with photosynthetic rate. However, little is known about the genetic correlation between grain yield and chlorophyll content in the same wheat mapping population. The primary goal of the study was to detect the genetic basis of grain yield and chlorophyll content and their possible roles in the genetic improvement of grain yield in wheat. Here, quantitative trait loci (QTLs) for grain yield and chlorophyll content were studied using a set of 168 doubled haploid (DH) lines derived from a cross between two elite Chinese wheat cultivars, Huapei 3×Yumai 57. The DH population and parents were evaluated for grain yield and chlorophyll content in three environments. A total of 11 additive QTLs and 6 pairs of epistatic QTLs were detected for grain yield and chlorophyll content. Loci, such as
on chromosomes (e.g. 2D, 4A, and 5D) simultaneously controling grain yield and chlorophyll content, showed tight linkages or pleiotropisms. Three novel major QTLs,
, closely linked with the PCR marker
on chromosome 5D, accounted for 10.32%, 12.95%, and 23.29% of the phenotypic variance, respectively. The favorable alleles came from Yumai 57.
A simple direct labeling method was used to synthesize the iodinated ultrafine polystyrene particles. The assay of X-ray photoelectron
spectroscopy (XPS) as well as Fourier-transform infrared (FT-IR) spectroscopy indicated the formation of stable covalent bond
to aryl group of the polymer particles. The purified radioiodinated product was incubated with serum of rat, and then evaluated
by in vitro stability test. The result showed that these synthesized ultrafine polystyrene particles were unmetabolized at
2 hours post-exposure, indicating the potential useful application of this labeled polymer particles as a promising probe
in biomedical sciences.
Authors:J. Chen, G. Hu, J. Zhang, C. Chu, and Y. Wu
Drought is a severe abiotic stress that affects wheat production worldwide. In order to identify candidate genes for tolerance to water stress in wheat, sequences of 11 genes that have function of drought tolerance in other plant species were used to identify the wheat ortholog genes via homology searching in the wheat EST database. Atotal of 11 primer pairs were identified and amplified PCR products in wheat. Of them, 10 STS markers were mapped on 11 chromosomes in a set of nulli-tetrasomic lines of ‘Chinese Spring’ wheat; six were mapped on chromosomes 1A, 1B, 4B, 7A, 2B and 5D, respectively, in a spring wheat mapping population (POP1). The marker XTaABH1 mapped on 7A in POP1 was the only one mapped but characterized in a winter wheat mapping population (POP2) for grain yield, kernel weight and diameter, and height in four-field trials applied different water stress or irrigation. The marker XTaABH1 was significantly associated with grain yield under rainfed condition, with kernel weight under terminal stress and non-irrigation conditions, with kernel diameter and height under non-irrigated condition. The STS primers, map information and marker-trait association produced in the currently study would be of interest to researchers working on drought tolerance.
With the continuous expansion of the global dairy trade market, the quality and safety of the Chinese dairy market have a wide and far-reaching impact on the world. Based on the development of the dairy scandal in the past few years in China, this study illustrates the serious damage of melamine on human health and the negative impact on the dairy industry in China.
This study shows that the lack of effective government regulations is a key reason for dairy market failure. Consumers are lacking confidence in the quality of Chinese dairy products and the government's market regulations. The Chinese dairy market will continue to rely on imported dairy products. By analyzing the typical cases of the dairy market in China, this study aims to provide a guide for dairy industries in other countries.
Authors:G. Zhong, S. Luan, P. Wang, Y. Guo, Y. Chen, and Y. Jia
thiourea complexes of antimony and bismuth triiodide were synthesized by a
direct reaction of antimony and bismuth triiodide with thiourea powder at
room temperature. The formula of the complex is MI3[SC(NH2)2]3(M=Sb, Bi). The crystal structure of the
complexes belongs to monoclinic system and the lattice parameters are a=1.4772 nm, b=1.6582
nm, c=2.0674 nm and β=90.81 for
and a=1.4009 nm, b=2.0170
nm, c=2.0397 nm and β=90.84 for
The infrared spectra reveal that the trivalent antimony or bismuth ion is
coordinated by the nitrogen atom, not the sulfur atom of the thiourea. Thermal
analysis shows that there are two times structure rearrangements or phase
transformation in the complexes from 100 to 170C.
Authors:Y. Guo, S. Luan, Y. Chen, X. Zang, Y. Jia, G. Zhong, and S. Ruan
New hexamethylenetetramine complexes of antimony and bismuth trichloride were synthesized through a solid phase reaction of
hexamethylenetetramine and antimony or bismuth trichloride. The formula of the complex is MCl3(C6H12N4)2⋅H2O (M=Sb, Bi).The crystal structure of the complexes belongs to monoclinic system and the lattice parameters: a=1.249 nm, b=1.4583 nm, c=1.6780 nm andβ=91.78 for SbCl3(C6H12N4)2⋅H2O and a=1.3250 nm, b=1.3889 nm, c=1.7449 nm and β=98.94 for BiCl3(C6H12N4)2⋅H2O. Far-infrared spectra reveal that the antimony or bismuth ion is coordinated by the nitrogen atom of the hexamethylenetetramine.
The thermal analysis also demonstrates the complex formation between the antimony or bismuth ion and hexamethylenetetramine.
The intermediate and final residues in the thermal decomposition process have been analyzed to check the pyrolysis reaction.