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Chen Z.,Capital Normal University | Tan L.,Capital Normal University | Hu L.,Capital Normal University | Luan Y.,Beijing Research Center for Agricultural Standards and Testing
Talanta | Year: 2015

Here, a simple, and highly sensitive fluorescent assay is designed to monitor K+. The versatile, robust biosensing strategy is based on the specific recognition utility of label-free aptamers with their targets and PicoGreen dye as the signal probe. The aptamers undergo a conformational change to a secondary structure such as G-quadruplex in the presence of targets. In addition to a conformational change with its targets, the remaining single-stranded DNA (ssDNA) aptamer form a duplex structure with its complete complementary sequence. Conformational changes of aptamers as well as fluorescence amplification produce clear signal-off in the presence of targets. Fluorescent assay employing this mechanism for the detection of K+ is highly sensitive, and selective. The detection limit of the K+ assay is determined to be 2.37 pM. The sensing strategy is low-cost and simple in its operation without requirement for complex labeling of probe DNA or sophisticated synthesis of the fluorescent compound. Also, the method has less structural requirement of complexes of aptamers with their targets, thus rending its wilder applications for various targets. © 2015 Elsevier B.V. All rights reserved. Source

Liu D.,China Agricultural University | Min S.,China Agricultural University | Ping H.,Beijing Research Center for Agricultural Standards and Testing | Song X.,China Agricultural University
Journal of Chromatography A | Year: 2016

A simple and rapid method was developed for evaluating 16 phthalic acid esters (PAEs) at the μg/kg level in a complex milk matrix using directly suspended droplet microextraction-gas chromatography mass spectrometry (DSDME-GC-MS). The different parameters for extraction and for the DSDME experiment were optimized, including You are free to submit the revised manuscript at a later date as a new submission.10. g/L trichloroacetic acid concentration, 100. μL cyclohexane micro-droplet organic solvent, 1100. rpm stirring speed, 10. min extraction time and no salt amount. Validation experiments showed good linearity (γ. > 0.9878, 0.002-0.4. μg/mL), satisfactory precision (RSD. <. 11%), and good accuracy (relative recovery of 70.2-108%) when analyzing milk samples using the optimized method. The limits of detection (LODs) ranged between 0.001 and 0.2. μg/L, and the limits of quantification (LOQs) ranged between 0.003 and 0.7. μg/L for 15 PAEs. Dinonyl phthalate (DINP) had a low response and did not have good linearity. The proposed method was successfully applied for the analysis of PAEs in real milk samples. © 2016 Elsevier B.V. Source

Li A.,Chinese Academy of Agricultural Sciences | Li A.,Beijing Research Center for Agricultural Standards and Testing | Ha Y.,Chinese Academy of Agricultural Sciences | Li Q.,Chinese Academy of Agricultural Sciences | And 3 more authors.
Journal of Chinese Institute of Food Science and Technology | Year: 2015

The types and content of trans fatty acid (TFA) formed in heated soybean oil were detected by capillary column-gas chromatography method. TFA was comparatively analyzed with physical and chemical indicators (Acid value, Carbonyl group value and Polarity composition) of soybrean oil withdifferent heating time. Soybean oil was heated by high temperature of 220℃ with forming the large amounts of TFAs, TFA content increased from control group of 0.075 g/100 g to 5.691 g/100 g after 12 h heating, the main species were trans linoleic acid and linolenic acid. Physical and chemical indicators such as acid value, carbonyl group value and polar components significantly increased (P<0.01) with heating time extended under temperature of 220℃, but longer heating time (more than 48 h) was needed to exceed the set limit value of these indicators. While the TFA content in the 12 h of heating time was more than 2 times of the recommended limits(2 g/100 g). This study provided a scientific support for establishing limited index of TFA and its control method in edible oils heated under high temperature. ©, 2015, Chinese Institute of Food Science and Technology. All right reserved. Source

Song X.,Beijing Academy of Agriculture and Forestry Sciences | Wang J.,Beijing Research Center for Agricultural Standards and Testing | Yang G.,Beijing Academy of Agriculture and Forestry Sciences | Feng H.,Beijing Academy of Agriculture and Forestry Sciences
Intelligent Automation and Soft Computing | Year: 2014

Grain protein content (GPC) is generally not uniform across cropland due to changes in landscape position, nutrient availability, soil chemical, physical properties, cropping history and soil type. It is necessary to determine the winter wheat GPC quality for different croplands in a collecting area in order to optimize the grading process. GPC quality evaluation refers not only the GPC value, but also the GPC uniformity across a cropland. The objective of this study was to develop a method to evaluate the GPC quality for different croplands through remote sensing technique. Three Landsat5 TM images were acquired on March 27, April 28 and May 30, 2008, corresponding to erecting stage, booting stage and grain filling stage of wheat. The wheat GPC was determined after harvest. Then multi linear regression (MLR) analysis with the enter method was calculated using the TM spectral parameters and the measured GPC data. The GPC MLR model was established based on multi-temporal spectral parameters. The accuracy of the model was R2>0.521, RMSE < 0.66%. The GPC mean value and standard deviation value for each cropland was calculated based on the ancillary cropland boundary data and the grain protein monitoring map. Winter wheat filed GPC quality was evaluated by the GPC mean value and GPC uniformity parameter - coefficients of variation (CV). The evaluation result indicated that the super or good level winter wheat croplands mainly lie in Tongzhou, Daxing and Shunyi County, while the middle or low GPC level croplands are mainly distributed on the Fangshang county. This study indicates that the remote sensing technique provides valuable opportunities to monitor and evaluate grain protein quality. © 2014, © 2014 TSI® Press. Source

Luan Y.,Beijing Research Center for Agricultural Standards and Testing | Chen Z.,Capital Normal University | Xie G.,Academy of State Administration of Grain | Chen J.,Beijing Research Center for Agricultural Standards and Testing | And 5 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2015

The selective detection of ultra trace amounts of aflatoxin B1 (AFB1) is extremely important for food safety, since it is the most toxic mycotoxin class that is allowed to be present in edible food and agricultural products with strictly Maximum Residue Limit (MRL). Sensitive detection of AFB1 residues requires time-consuming techniques and expensive instruments. An aptasensor for AFB1 detection, using unmodified gold nanoparticles (AuNPs) indicator, was developed in the present study, based on the salt-induced AuNPs aggregation phenomenon. Its linear dynamic range and detection sensitivity were found to be 0.025 ng/mL-100 ng/mL and 0.025 ng/mL of AFB1 respectively, which were lower than the maximum residue limit (MRL) in edible food, as set by China and the European Commission. Our study provides a simple, fast, and visible method for AFB1 analysis, with high sensitivity, which can be applied in future on-site detection for food and agricultural products. Copyright © 2015 American Scientific Publishers. Source

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