Longitudinal changes in the hypothalamic-pituitary-adrenal axis and sympathetic nervous system are related to the prognosis of stroke.

Background and purpose: This study sought to improve methods to identify biomarkers in the neuroendocrine system related to stroke progression to improve the accuracy of traditional tools for evaluating stroke prognosis. Methods: Seventy-four stroke patients and 237 healthy controls were prospectively included. We measured urinary epinephrine (E), noradrenaline (NE), dopamine (DA) and cortisol (F) on days 1, 3, and 5 after stroke onset and plasma F, adrenocorticotropic hormone (ACTH), thyrotropin (TSH), prolactin (PRL), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and growth hormone (GH). The correlation between these hormone levels and 90-day prognosis was analyzed, their value in assessing prognosis was compared with lesion volume and National Institutes of Health Stroke Scale (NIHSS) scores using receiver operating characteristic (ROC) curves, and their correlation with conventional clinical variables was assessed. Results: Levels of F, 24-h urinary free cortisol(UFC), E, NE, DA, and GH on days 1, 3, and 5 were significantly higher in stroke patients than in controls (P < 0.01), while ACTH and TSH decreased, gradually approaching normal within 5 days of onset. Levels of E, NE, F, and 24-h UFC were proportional to severity, and all gradually decreased within 5 days of onset in patients with a good prognosis and gradually increased or remained high in those with a poor prognosis. After adjustment for age, sex, NIHSS, or Glasgow Coma Scale (GCS) score, F > 13.6 µg/dL, ACTH > 22.02 pg/mL and NE > 123.5 µg/ 24 h were identified as risk factors for a poor prognosis 90 days after stroke (P < 0.05). The combination of F, ACTH, NE, white blood cell count (WBC), glucose (Glu), and hemoglobin (Hb) was significantly more accurate than lesion volume (AUC: 0.931 vs. 0.694 P = 0.019) and NIHSS score (AUC: 0.931 vs. 0.746 P = 0.034) in predicting poor prognosis of stroke 1 day after onset. Hormones and traditional clinical variables were correlated to varying degrees, with NE correlating most strongly with 24-h UFC (r = 0.54) and moderately positively with lesion volume (r = 0.40) and NIHSS score (r = 0.45). Conclusions: Stroke causes significant time-phased dynamic changes in the hypothalamic-pituitary-adrenal axis and sympathetic nervous system, and plasma F, ACTH, and urinary NE levels can be used to assess stroke severity and prognosis. Chinese clinical trial registry: Registration Number: ChiCTR1900024992. Registration Date: 2019/8/6.

Time-varying spillovers among pilot carbon emission trading markets in China.

Clarifying the time-varying spillovers among pilot carbon emission permit trading markets in China is an important foundation for building the national carbon emission trading market. We calculate the dynamic spillover of carbon price return among the pilot carbon emission permit trading markets in China with the time-varying connectedness approach. The dataset is constructed from transaction data from seven pilot carbon markets in China during the period of June 23, 2014, to December 31, 2020. The quantitative analysis suggests that (i) Beijing and Chongqing carbon emission trading markets are the main spillover markets of carbon price returns, with strong pricing power, while the Guangdong and Tianjin markets are the main receivers of the price return spillover in other pilot carbon emission trading markets. (ii) The spillover effect among China's carbon markets has a strong policy orientation. The improvement and development of the carbon market driven by macroeconomic regulation and control policies can effectively improve the spillover ability of the carbon market, and the market trading activity, namely the volatility of the carbon price return rate, can amplify the spillover ability of the carbon market in the short term. (iii) There exist three types of price return spillover among China's pilot carbon emission trading markets, including central divergence, one-way chain transmission, and circular spillover. Along with the improvement of market operation efficiency, the central divergent type of spillover shifts to the pattern of circular spillover. It is necessary for the government to improve market efficiency and ensure the coordinated development of China's pilot carbon emission trading market and national carbon emission trading market.

The Fate of SWCNTs in Mouse Peritoneal Macrophages: Exocytosis, Biodegradation, and Sustainable Retention.

The understanding of toxicological and pharmacological profiles of nanomaterials is an important step for the development and clinical application of nanomedicines. Carbon nanotubes (CNTs) have been extensively explored as a nanomedicine agent in pharmaceutical/biomedical applications, such as drug delivery, bioimaging, and tissue engineering. The biological durability of CNTs could affect the function of CNTs-based nanomedicines as well as their toxicity in cells and tissues. Therefore, it is crucial to assess the fate of nanomedicine in phagocytes. Herein, we investigated the candidate fate of acid-oxidized single-walled carbon nanotubes (SWNCTs) in non-activated primary mouse peritoneal macrophages (PMQ). The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results showed that the intracellular SWCNTs continued growing from 4 to 36 h in PMQ. After replacing the exposure medium, we found the exosome induced by SWCNTs on the surface of macrophages according to scanning electron microscope (SEM) observation. The near-infrared (NIR) absorption increase of the supernatant samples after post-exposure indicates that SWCNTs exocytosis occurred in PMQ. The decreasing intracellular SWCNTs amount suggested the incomplete biodegradation in PMQ, which was confirmed by Raman spectroscopy and transmission electron microscopy (TEM). The combined data reveal that SWCNTs could be retained for more than 60 h in macrophages. Then sustainable retention of SWCNTs in primary macrophages was coexist with exocytosis and biodegradation. The findings of this work will shed light on the bioimaging, diagnosis and other biomedical applications of CNTs-based nanomedicines.

Residue investigation of some phenylureas and tebuthiuron herbicides in vegetables by ultra-performance liquid chromatography coupled with integrated selective accelerated solvent extraction-clean up in situ.

BACKGROUND: Some trace amounts of urea herbicide residues can be transferred to humans via the food chain, thereby being potentially harmful to human health. The development of a robust analytical methodology for effective sample preparation and simultaneous determination of herbicide residues in vegetable samples is required for achieving food safety. RESULTS: The diuron-molecularly imprinted polymers (MIPs) synthesized have excellent affinity and high selectivity to phenylureas (monolinuron, isoproturon, diuron and linuron) and tebuthiuron. A novel automated procedure with better selectivity for vegetable sample treatment was developed by integrated matrix solid-phase dispersion-accelerated solvent extraction clean-up in situ. Five herbicides can be baseline separated with runtime down to 5 min by ultra-performance liquid chromatography, and good linearity was obtained with a correlation coefficient (r) of 0.9999. The limit of quantification of the method was in the range of 0.8-2.3 µg kg-1 . Diuron residue in cherry tomato sample was found to be 40 µg kg-1 . CONCLUSION: The developed method has satisfactory selectivity, good linearity, high sensitivity and accuracy as well as speediness, and can ensure rapid selective extraction and sensitive multi-residue analysis at low microgram per kilogram levels of the herbicides in vegetable food. © 2018 Society of Chemical Industry.

Rapid selective accelerated solvent extraction and simultaneous determination of herbicide atrazine and its metabolites in fruit by ultra high performance liquid chromatography.

A selective accelerated solvent extraction procedure achieved one step extraction and cleanup for analysis of herbicide atrazine and its metabolites in fruit. Using a BEH C18 analytical column and the gradient mode with 2 mM ammonium acetate aqueous solution/acetonitrile as a mobile phase achieved effective chromatographic separation of the five analytes within 4 min. The calibration curves were linear over two orders of magnitude of concentration with correlation coefficients (r) of 0.9996-0.9999. The method limit of quantification was 1, 2, 1.5, 3, and 2 µg/kg for atrazine, desethylatrazine, desisopropylatrazine, desethyldesisopropylatrazine, and hydroxyatrazine, respectively, in the case of atrazine it is at least two orders of magnitude lower than the maximum residue limit (0.25 mg/kg). The intra-day and inter-day precisions of the five analytes were in the range of 2.1-3.5 and 3.1-4.8 %, respectively. The recoveries of the five analytes at three spiked levels varied from 85.9 to 107% with a relative standard deviation of 1.8-4.9% for pear and apple samples. The ultra high performance liquid chromatography with diode array detection method was proved to be fast, inexpensive, selective, sensitive, and accurate for the quantification of the analytes in pear and apple samples.

Biomimetic Modification and In Vivo Safety Assessment of Superparamagnetic Iron Oxide Nanoparticles.

The efficacy of superparamagnetic iron oxide nanoparticles (SPIONs) for biomedical applications depends on the magnetic properties, long time stability in biological fluids, and specific targeting capacity. The properties of SPIONs were generally improved by surface modification, but common modification technologies were usually conducted with multi-steps under rigid conditions. In this work, a facile and simple approach to synthesize functionalized SPIONs contrast agents was set up. First of all, SPIONs were prepared by an improved ultrasonic co-precipitation method. Then the surfaces of these SPIONs were modified biomimeticly by dopamine (DA) with strong adhesion. At last, the c(RGDyK), a biomolecule with the capacity of specific targeting capacity towards liver tumor cells, were coupled with DA on SPIONs via Mannich reaction. Thus the novel magnetic composite nanoparticles (abbreviated as c(RGDyK)-PDA-SPIONs) were successfully prepared. The as-synthesized nanoparticles were characterized by scanning electron microscope (SEM), dynamic light scattering, magnetic hysteresis loop measuring instrument. As a result, that the c(RGDyK)-PDA-SPIONs had an average size of about 50 nm and uniform distribution, and had superparamagnetic properties, good water dispersion stability. The acute toxicity test of the assynthesized c(RGDyK)-PDA-SPIONs to mice was also investigated. It was observed that LD50 of c(RGDyK)-PDA-SPIONs was 4.38 g/kg, with a 95% confidence interval ranging from 3.49 g/kg to 5.87 g/kg. These results indicated the novel c(RGDyK)-PDA-SPIONs had excellent biocompatibility, which was endowed with a potential capacity to serve as MRI contrast agents in diagnosis and treatment of the liver tumor.

Investigation of six bioactive anthraquinones in slimming tea by accelerated solvent extraction and high performance capillary electrophoresis with diode-array detection.

A rapid and effective method for effective separation and rapid simultaneous determination of six bioactive anthraquinones by capillary zone electrophoresis was developed. An accelerated solvent extraction procedure was used for the extraction of anthraquinones from slimming tea. Under the optimized conditions, the effective separation of six anthraquinones was achieved within 8 min. Good linearity was achieved, with a correlation coefficient (r) of ⩾ 0.999. The limit of detection ranged from 0.33 to 1.40 µg mL(-1). The intra- and inter-day relative standard deviation (RSD) of the six analytes was in the range of 2.3-3.9% and 3.2-4.9%, respectively. The average recovery of the six analytes from real tea samples was in the range of 86.15-98.30% with the RSD of 1.04-4.99%. The developed and validated method has speediness, high sensitivity, recovery and precision, and can be applied for the quality control of slimming tea.

Development of multi-residue analysis of herbicides in cereal grain by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry.

A rapid and sensitive method was developed for the determination of 50 herbicides in cereal grain by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS). Using acetonitrile effectively extracted 22 kinds of triazine and other basic herbicides, and using 90:10 v/v acetonitrile-phosphate buffer (pH = 7.5) effectively extracted other 28 herbicides. Chromatographic separation was achieved using gradient elution with acetonitrile-water as a mobile phase for 22 triazine and phenylurea herbicides and with 5mM ammonium acetate aqueous solution containing 0.1% formic acid-acetonitrile as a mobile phase for other 28 herbicides. Using matrix-matched standard calibration curve effectively reduced the indirect matrix effects, ensured accurate quantification for these herbicides. The response was linear over two orders of magnitude with a correlation coefficients (r(2)) higher than 0.992. The limits of quantification for the herbicides varied from 0.2 to 25.6 µg kg(-1). The intra- and inter-day precisions (relative standard deviation, RSD) were 2.2-9.3% and 5.7-17.1%, respectively. The recovery varied from 61.6% to 110% with the RSD of 1.6-11.8%. Analyzing soybean, corn and wheat samples from 17 counties evaluated this method. The developed and validated method has high sensitivity, satisfactory recovery and precision, can ensure the multi-class multi-residue analysis at low µg kg(-1) level for the most herbicides in cereal grain.

Trace residue analysis of dicyandiamide, cyromazine, and melamine in animal tissue foods by ultra-performance liquid chromatography.

An effective sample preparation procedure using an accelerated solvent extraction (ASE) procedure, followed by cleaning with melamine molecularly imprinted polymers solid-phase extraction (MISPE) was developed. A novel and highly sensitive ASE-MISPE-ultra-performance liquid chromatography (UPLC) method was developed for effective separation and simultaneous determination of dicyandiamide (DCD), cyromazine (CYR), and melamine (MEL) in complex animal tissue foods. Under optimized conditions, good linearity was achieved with a correlation coefficient (r) of 0.9999 in the range of at least two orders of magnitude. The limit of quantification of the method was 1.7 µg/kg, 5.0 µg/kg, and 3.2 µg/kg for DCD, MEL, and CYR, which was three orders of magnitude smaller than the maximum residue limits (MRLs). The intra- and inter-day precisions (in terms of the relative standard deviation, RSD) of the three analytes were in the range of 1.7-3.1% and 3.1-6.3%, respectively. The average recoveries of analytes from blank chicken, beef, mutton, pork, and pig liver samples spiked with the three levels varied from 91.2% to 107% with RSD of 1.7-8.3% for DCD, 89.0-104% with RSD of 2.1-6.1% for CYR, and 94.8-105% with RSD of 1.1-6.6% for MEL. The proposed method has the characteristics of speed, sensitivity, and accuracy, and can be used for the routine determination of DCD, CYR, and MEL at the µg/kg level in complex animal tissue foods.

Multi-class, multi-residue analysis of trace veterinary drugs in milk by rapid screening and quantification using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry.

A simple and rapid multi-class multi-residue analytical method was developed for the screening and quantification of veterinary drugs in milk by ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). A total of 90 veterinary drugs investigated belonged to almost 20 classes including lincomycins, macrolides, sulfonamides, quinolones, tetracyclines, ß-agonists, ß-lactams, sedatives, ß-receptor antagonists, sex hormones, glucocorticoids, nitroimidazoles, benzimidazoles, nitrofurans, and some others. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure was developed for the sample preparation without the solid-phase extraction step. The linearity, sensitivity, accuracy, repeatability, and reproducibility of the method were fully validated. The response of the detector was linear for each target compound in a wide concentration range with a correlation coefficient (R(2)) of 0.9973 to 0.9999 (among them R(2)>0.999 for 73 of 90 analytes). The range of the limit of quantification for these compounds in the milk ranged from 0.10 to 17.30µg/kg. The repeatability and reproducibility were in the range of 2.11 to 9.62% and 2.76 to 13.9%, respectively. The average recoveries ranged from 72.62 to 122.2% with the RSD (n=6) of 1.30 to 9.61% at 3 concentration levels. For the screening method, the data of the precursor and product ions of the target analytes were simultaneously acquired under the all ions MS/MS mode in a single run. An accurate mass database for the confirmation and identification of the target compounds was established. The applicability of the screening method was verified by applying to real milk samples. The proposed analytical method allows the identification and confirmation of the target veterinary drugs at trace levels employing quick analysis time. Certain veterinary drugs were detected in some cases.

Synthesis and evaluation of dummy molecularly imprinted microspheres for the specific solid-phase extraction of six anthraquinones from slimming tea.

Dummy molecularly imprinted microspheres with danthron as template were synthesized and their performance was evaluated. Accelerated solvent extraction can rapidly and effectively remove template molecules from the microspheres. The microspheres were applied as a specific sorbent for solid-phase extraction of six anthraquinones from slimming tea, showing excellent affinity and high selectivity to danthron and the target analytes. The molecular recognition mechanisms were discussed by the experimental validation with IR spectroscopy. The sample was treated using accelerated solvent extraction followed by dummy molecularly imprinted microspheres solid-phase extraction. Under the optimized ultra high performance liquid chromatographic conditions, the six target analytes can be baseline separated in 8 min, and good linearity was obtained in a range of 0.1-40 µg/mL with the correlation coefficient (r(2)) of ≥0.9998. The method limit of quantification was in a range of 1-2 mg/kg, it can ensure analysis of anthraquinones at mg/kg level. The intra- and interday precision (RSD, n = 6) for the analysis of the six analytes in a slimming tea was less than 4.5 and 5.4%, respectively. The developed method can be applied for the selective extraction, effective separation, and rapid determination of six anthraquinones in slimming tea.

Highly sensitive determination of cyromazine, melamine, and their metabolites in milk by molecularly imprinted solid-phase extraction combined with ultra-performance liquid chromatography.

A novel molecularly imprinted solid-phase extraction-ultra-performance liquid chromatography (MISPE-UPLC) method for effective separation and simultaneous determination of cyromazine, melamine, and their metabolites (ammeline and ammelide) in milk samples was developed. Molecularly imprinted polymers (MIP) were synthesized in an ethanol-water system, with melamine as the template and methacrylic acid as the organic functional monomer. The MIP were applied as a specific sorbent for the selective solid phase extraction of cyromazine, ammelide, melamine and ammeline. The molecular recognition mechanism was investigated by molecular simulation and the experiment was validate by using Fourier transform infrared spectroscopy and (1)H nuclear magnetic resonance spectroscopy. A new mechanism based on the formation of both an amido group and hydrogen bonds was developed. A binding study demonstrated that the MIP showed excellent affinity to and high selectivity for melamine and related compounds. Under optimized conditions, we achieved good linearity of the calibration curves with correlation coefficients >0.999. Low limits of quantification (LOQ) for the method were determined to be 1.25, 1.25, 2.59, and 6.42 µg/kg for cyromazine, ammelide, melamine, and ammeline, respectively, which were 3 orders of magnitude smaller than the maximum residue limit (MRL). The high sensitivity of this method allows detection at the microgram per kilogram level. The proposed MISPE-UPLC method is a highly selective and sensitive method for determination of cyromazine, melamine, and their metabolites (ammeline and ammelide) for use in the control and quality assurance of milk.

Study on the interaction characteristics of cefamandole with bovine serum albumin by spectroscopic technique.

The interaction of cefamandole with bovine serum albumin (BSA) was studied by fluorescence quenching in combination with UV-Vis spectroscopic method under near physiological conditions. The fluorescence quenching rate constants and binding constants for BSA-cefamandole system were determined at different temperatures. The fluorescence quenching of BSA by cefamandole is due to static quenching and energy transfer. The results of thermodynamic parameters, ΔH (-268.0 kJ mol(-1)), ΔS (-810.0 J mol(-1) K(-1)) and ΔG (-26.62 to -8.52 kJ mol(-1)), indicated that van der Waals interaction and hydrogen bonding played a major role for cefamandole-BSA association. The competitive experiments demonstrated that the primary binding site of cefamandole on BSA was located at site III in sub-domain IIIA of BSA. The distance between cefamandole and a tryptophane unit was estimated to be 1.18 nm based on the Förster resonance energy transfer theory. The binding constant (KA) of BSA-cefamandole at 298 K was 2.239×10(4) L mol(-1). Circular dichroism spectra, synchronous fluorescence and three-dimensional fluorescence studies showed that the presence of cefamandole could change the conformation of BSA during the binding process.

Gene expression profiling analysis of locus coeruleus in idiopathic Parkinson's disease by bioinformatics.

This study aimed to explore the underlying molecular mechanisms of idiopathic Parkinson's disease (IPD) by bioinformatics analysis. Gene expression profile GSE34516 was downloaded from the Gene Expression Omnibus. Eight locus coeruleus post-mortem tissue samples derived from four IPD patients and four neurological healthy controls were used to identify the differentially expressed genes (DEGs) by paired t test. Based on the DEGs, principal components were analyzed. The Gene Ontology functional and Kyoto Encyclopedia of Genes and Genomes pathway analysis of the genome microarray data were then performed. Finally, protein-protein interaction (PPI) network of the DEGs was constructed. Total 261 DEGs including 195 up-regulated and 66 down-regulated DEGs were identified. Intracellular protein transport and RNA splicing via transesterification reactions were selected as the most two significantly enriched functions. Mismatch repair, N-glycan biosynthesis, spliceosome and nucleotide excision repair were the significantly enriched pathways. In the PPI network, CTSS, CD53, IGSF6, PTPRC and LAPTM5 were the hub nodes. Intracellular protein transport and RNA splicing via transesterification reactions were closely associated with IPD. The DEGs, such as CX3CR1, SLC5A7, CD53 and PTPRC may be the potential targets for IPD diagnosis and treatment.

Residues investigation of fluoroquinolones and sulphonamides and their metabolites in bovine milk by quantification and confirmation using ultra-performance liquid chromatography-tandem mass spectrometry.

A novel UPLC-MS/MS method for quantification and confirmation of eight fluoroquinolones, five sulphonamides (SAs) and four acetyled metabolites in milk is developed. Their main fragmentation pathways were presented. The limits of quantification were in the range of 0.01-0.29 µg kg(-1) for FQs and 0.13-1.68 µg kg(-1) for SAs. Mean recoveries ranging from 61% to 115% were achieved at spiked level of 0.5-100 µg kg(-1). The intra- and inter-day precisions were in the range of 6.3-10.7% and 9.0-13.4%, respectively. This novel approach has high speed and sensitivity, and can ensure the multiclass and multiresidue analysis of bovine milk at low µg kg(-1) level. The content of each analyte residue is much lower than the maximum residue limits. Some residues in milk were confirmed in according to the Commission Decision 657/2002/EC.

Analysis of dissolved organic matters in Fu River of Baoding using three dimensional fluorescence excitation-emission matrix.

The fluorescence properties of dissolved organic matter (DOM) in Fu River in Baoding were investigated by three-dimensional fluorescence spectrometry. The type, distribution and origin of the DOM were estimated on basis of the position, number and intensity of fluorescence peaks in the spectra. Two types of fluorescence peaks were detected from Fu River. There are protein-like fluorescence peaks A with Ex/Em = 225-230/340 nm and soluble microbial metabolites peaks B with Ex/Em=275/340-350 nm. The protein-like fluorescence peaks and soluble microbial metabolites peaks were founded in different times and stations in Fu River. Certain correlation was observed between the fluorescence intensity of DOM and the water quality parameters of Fu River. Good correlation of different fluorescence peaks showed the same of source. The fluorescence intensity of the two types had a significant positive relationship with COD, TN, TP and NH3-N concentration, this phenomenon indicating that the fluorescence peaks can speculate the level of pollution of Fu River. These results provided a reference for the pollution control in Fu River.

Research on degradation of penicillins in milk by ß-lactamase using ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry.

The degradation of penicillin G, penicillin V, and ampicillin in milk in the presence of ß-lactamase was investigated by ultra-performance liquid chromatography coupled with electrospray ionization-time-of-flight mass spectrometry. Degradation products of the 3 penicillins in milk were identified based on the fact that the metabolites or degradation products contain a substructure of penicillin, and their degradation pathways in acidic milk in presence of ß-lactamase were developed. The influence of factors on the degradation was investigated, including ß-lactamase dosage, temperature, time, and acidity. The ratio of the 2 degradation products (penicilloic acid and penilloic acid) is different at different temperatures and pH. Penicilloic acid was the dominant species obtained at pH 6 under 40°C, but, being unstable, it could not be used as a standard for accurate analysis of penicilloic acid, and also could not be used as target for detection of penicillins in milk. Penilloic acid was the dominant species obtained at pH 2 above 40°C; it was stable and could be used as a standard for quantitative analysis and as target for detecting whether penicillins were used in milk.

A sensitive and validated HPLC method for the determination of cyromazine and melamine in herbal and edible plants using accelerated solvent extraction and cleanup with SPE.

A highly sensitive method was developed for the determination of the residues of cyromazine (CYR) and its metabolite, melamine (MEL), in herbal and edible plant samples by using reversed phase high-performance liquid chromatography-diode-array detection (RP-HPLC-DAD) with accelerated solvent extraction and solid phase extraction cleanup. The conditions of separation and detection were investigated and optimized. A Waters C18 column (250 × 4.6 mm i.d., 5 µm) was used for the RP-HPLC, with a mobile phase composed of 0.1% trifluoroacetic acid solution and methanol (85:15, v/v, pH 2.6). Under the optimized conditions, good linearity was achieved with a correlation coefficient of 0.9998. The limits of quantification of the method were 2.15 µg/kg for CYR and 2.51 µg/kg for MEL, which are maximum residue limits as low as three orders of magnitude. The recovery values at three spiked concentrations were in the range of 96.2-107.1% with relative standard deviations (RSDs) of 1.1-5.7% for CYR, and 92.7-104.9% with RSDs of 1.7-6.1% for MEL. The proposed method allows detection at levels as low as µg/kg levels for CYR and MEL. The method was validated by liquid chromatography-tandem mass spectrometry, and can be used for the routine determination of CYR and MEL in herbal and edible plant samples with the characteristics of speed, high sensitivity and accuracy, and low consumption of reagents.

Preparation of doxycycline-imprinted magnetic microspheres by inverse-emulsion suspension polymerization for magnetic dispersion extraction of tetracyclines from milk samples.

A magnetic dispersion extraction method was developed based on a molecularly imprinted magnetic microsphere (MIMM) for the selective clean-up and enrichment of tetracycline antibiotics from milk samples. The MIMMs were prepared by inverse-emulsion suspension polymerization, using doxycycline, trimethylolpropane trimethacrylate, acrylamide, methacrylic acid, and surface-modified Fe3 O4 as a template molecule, crosslinker, functional monomer, and magnetic component, respectively. Synthesis and extraction conditions were optimized for obtaining excellent affinity and high selectivity. The magnetism, covering amount, and selectivity of the magnetic microspheres were characterized by a vibrating sample magnetometer, thermogravimetric analysis, and a competitive recognition experiment. The MIMMs were applied to separate tetracycline antibiotics from milk samples by magnetic dispersion extraction, and an enrichment factor of 9.28 and a good sample clean-up were obtained. The average recoveries of four tetracycline antibiotics were obtained in the range of 74.5-93.8% with a precision of 1.2-5.2%. The LODs and LOQs of the proposed method were in the range of 7.4-19.4 and 24.7-64.7 µg/kg, respectively. The results indicated that magnetic dispersion extraction using MIMMs is a powerful tool for food-sample pretreatment with high selectivity and a simplified procedure.

[Identification of geographical origins of rice with pattern recognition technique by near infrared spectroscopy].

A rapid method was developed for discrimination of the geographical origins of rice with pattern recognition technique by near infrared spectrocopy (NIRS). A total of 119 geography signs product Xiangshui rice samples and 90 rice (Non-Xiangshui rice) samples produced from other places were analyzed by NIRS. After first derivative and smooth processing, principal component analysis (PCA) was used to reduce the dimensionality of the spectral data. Through the loading graph of the first three principal components, characteristic wave band (7 700-6 700, 5 700-4 300 cm(-1)) with max-relativity was determined. In whole wave, using agglomerative hierarchical cluster analysis and Fisher's linear discriminant, the discrimination of Xiangshui rice and Non-Xiangshui rice was all 100%. The correct rate of specific geographical origins of Non-Xiangshui rice was 91.9% by cluster analysis and 96.7% by discriminant analysis. For analysis in the characteristic wave bands, the correct rate of discriminant by cluster analysis was higher than the analysis result through the range of the whole band. Therefore, characteristic wave band has strong representativeness. The results indicate that it is feasible to discriminate the geographical origins of rice with pattern recognition technique by NIRS, and selecting characteristic wave band is one of the validated methods to improve the precision of the discrimination mode.