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991.
Portable paper‐based device for quantitative colorimetric assays relying on light reflectance principle 下载免费PDF全文
This paper presents a novel paper‐based analytical device based on the colorimetric paper assays through its light reflectance. The device is portable, low cost (<20 dollars), and lightweight (only 176 g) that is available to assess the cost‐effectiveness and appropriateness of the original health care or on‐site detection information. Based on the light reflectance principle, the signal can be obtained directly, stably and user‐friendly in our device. We demonstrated the utility and broad applicability of this technique with measurements of different biological and pollution target samples (BSA, glucose, Fe, and nitrite). Moreover, the real samples of Fe (II) and nitrite in the local tap water were successfully analyzed, and compared with the standard UV absorption method, the quantitative results showed good performance, reproducibility, and reliability. This device could provide quantitative information very conveniently and show great potential to broad fields of resource‐limited analysis, medical diagnostics, and on‐site environmental detection. 相似文献
992.
An atom-economical synthesis of chiral polyfunctionalized spiropyrazolone derivatives based on the development of a new organocatalytic enantioselective one-pot sequential Michael/Michael/Aldol reaction of 1,3-dicarbonyl compounds with unsaturated pyrazolones and α,β-unsaturated aldehydes has been developed. The notable features of this one-pot sequential process include the generation of up to six consecutive stereogenic carbon centers including one quaternary stereocenter and five tertiary stereocenters with high enantioselectivities (up to 95% ee) and excellent diastereoselectivities (>99:1 d.r.). 相似文献
993.
Katsuya Sako Toshiaki Kakehi Shota Nakano Hiroyuki Oku Xu Feng Shen Tetsuo Iwanaga Manami Yoshikawa Kouta Sugahara Shinji Toyota Hiroyuki Takemura Teruo Shinmyozu Michito Shiotsuka Hitoshi Tatemitsu 《Tetrahedron letters》2014
Two novel redox-active 1,3-dithiole (DT) ring-fused 4,5-diazafluorene ligands with crown ether moieties (L1 and L2) were synthesized and characterized. The crystal structure of L1 was studied. The electrochemical and spectroscopic properties of these new ligands, as well as the corresponding bis(bipyridine)ruthenium(II) complexes [4: Ru L1(bpy)2 and 5: Ru L2(bpy)2], were also been investigated. 相似文献
994.
The element content in rock sample can be determined by prompt gamma ray activation analysis technology. The neutron distributions under the conditions with different moderating materials, moderator size and distance from neutron source to lead-out hole were simulated using Monte Carlo method, and then the optimal structure parameters to get the highest thermal neutron flux was obtained. The PGNAA system with optimal parameters based on 252Cf neutron source was founded. In addition, the rock and element standard samples were irradiated by thermal neutron in this system. Moreover, the element content was calculated by processing gamma ray spectroscopy recorded, and it is in agreement with result of XRF method. 相似文献
995.
Xiao-gui Feng Qian-ge He Jian-chen Wang Jing Chen 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(1):509-516
90Sr is a product of nuclear fission, the radioactivity of which can be determined by liquid scintillation counting (LSC). Because the LSC spectra of 90Sr and its daughter 90Y overlap each other, the following methods are usually used: (1) measuring immediately after 90Sr/90Y separation; (2) waiting to reach radioactive equilibrium; (3) adopting the conventional 2-window approach; and (4) using the spectra deconvolution technique. The first one requires 90Sr/90Y separation and immediate measurement; the second one is time-consuming; the third one is valid only for samples with the same quench level as the calibration standard; the last one is somewhat complicated, and in some cases it is not convenient to export the experimental data to some deconvolution software. Therefore, we have developed a modified 2-window approach to rapidly determine 90Sr and 90Y in either equilibrium or disequilibrium at low quench level. The key modification of the approach is to provide an LSC spectrum of pure 90Y with the same quench level as the sample to be determined. This modification eliminates the need to conduct 90Sr/90Y separation for the sample itself, to prepare the quench curves, and to fit the LSC spectra with some deconvolution software. 相似文献
996.
建立了阳离子交换模式在线固相萃取-液相色谱串联质谱法检测牛奶中14种磺胺药物方法。取5 g样品用15 mL乙腈提取和除蛋白,提取液于50℃氮气吹干后,用1.00 mL 0.2%甲酸溶解,溶解液通过双三元液相色谱用阳离子在线固相萃取柱在线富集净化,2%氨水甲醇/0.2%甲酸(50:50,V/V)洗脱。然后转移至C18色谱柱上进行分离,再用串联四级杆质谱检测。结果表明,14种磺胺类药物在0.1~10μg/kg含量范围内线性良好(r≥0.999);方法的检出限为0.05μg/kg,定量限为0.1μg/kg;方法回收率在60%~90%范围内,批内和批间相对标准偏差都小于10%。本方法较传统固相萃取柱净化法更简捷、经济和稳定。 相似文献
997.
Enrichment of neonicotinoid insecticides from lemon juice sample with magnetic three‐dimensional graphene as the adsorbent followed by determination with high‐performance liquid chromatography 下载免费PDF全文
A novel 3D‐graphene (3D‐G) magnetic nanomaterial was prepared and used as an adsorbent for the extraction of four neonicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid, and thiamethoxam) from lemon juice sample. Then, HPLC with UV detection was applied for the determination of the neonicotinoid insecticides desorbed from the 3D‐G magnetic nanomaterial. The main experimental parameters that affect the extraction efficiencies such as the amount of 3D‐G magnetic nanomaterial, sample solution pH, extraction time, salting‐out effect, and desorption conditions were studied and optimized. As a result, the linear concentration range of the method was from 0.3 to 100.0 ng/mL for thiacloprid, from 0.5 to 100.0 ng/mL for imidacloprid and acetamiprid, and from 1.0 to 100.0 ng/mL for thiamethoxam, with correlation coefficients of 0.9965–0.9985, respectively. The LODs of the method based on an S/N of 3 were between 0.08 and 0.2 ng/mL. The enrichment factors obtained were between 67 and 427, and the RSDs (n = 6) were in the range from 4.6 to 7.1%, and the recoveries of the method fell in the range of 88.75 to 111.60%. 相似文献
998.
A quick,easy, cheap,effective, rugged,and safe sample pretreatment and liquid chromatography with tandem mass spectrometry method for the simultaneous quantification of 33 mycotoxins in Lentinula edodes 下载免费PDF全文
Zheng Han Zhihong Feng Wen Shi Zhihui Zhao Yongjiang Wu Aibo Wu 《Journal of separation science》2014,37(15):1957-1966
Lentinula edodes, one of the most cultivated edible fungi in the world, are usually neglected for mycotoxins contamination due to the initial thinking of its resistance to mycotoxingenic molds. In the present study, a sensitive and reliable liquid chromatography with tandem mass spectrometry method was developed for the simultaneous quantification of 33 mycotoxins in L. edodes. Targeted mycotoxins were extracted using a quick, easy, cheap, effective, rugged, and safe procedure without any further clean‐up step, and analyzed by liquid chromatography with tandem mass spectrometry on an Agilent Poroshell 120 EC‐C18 column (100 × 3 mm, 2.7 μm) with a linear gradient elution program using water containing 5 mM ammonium acetate and methanol as the mobile phase. After validation by determining linearity (R2 > 0.99), sensitivity (LOQ ≤ 20 ng/kg), recovery (73.6–117.9%), and precision (0.8–19.5%), the established method has been successfully applied to reveal the contamination states of various mycotoxins in L. edodes. Among the 30 tested samples, 22 were contaminated by various mycotoxins with the concentration levels ranging from 3.3–28 850.7 μg/kg, predicting that the edible fungus could be infected by the mycotoxins‐producing fungi. To the best of our knowledge, this is the first report about real mycotoxins contamination in L. edodes. 相似文献
999.
Development of a solid‐phase microextraction fiber by the chemical binding of graphene oxide on a silver‐coated stainless‐steel wire with an ionic liquid as the crosslinking agent 下载免费PDF全文
Min Sun Juanjuan Feng Yanan Bu Huimin Duan Xiaojiao Wang Chuannan Luo 《Journal of separation science》2014,37(24):3691-3698
Graphene oxide was bonded onto a silver‐coated stainless‐steel wire using an ionic liquid as the crosslinking agent by a layer‐by‐layer strategy. The novel solid‐phase microextraction fiber was characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and Raman microscopy. A multilayer graphene oxide layer was closely coated onto the supporting substrate. The thickness of the coating was about 4 μm. Coupled with gas chromatography, the fiber was evaluated using five polycyclic aromatic hydrocarbons (fluorene, anthracene, fluoranthene, 1,2‐benzophenanthrene, and benzo(a)pyrene) as model analytes in direct‐immersion mode. The main conditions (extraction time, extraction temperature, ionic strength, and desorption time) were optimized by a factor‐by‐factor optimization. The as‐established method exhibited a wide linearity range (0.5–200 μg/L) and low limits of determination (0.05–0.10 μg/L). It was applied to analyze environmental water samples of rain and river water. Three kinds of the model analytes were quantified and the recoveries of samples spiked at 10 μg/L were in the range of 92.3–120 and 93.8–115%, respectively. The obtained results indicated the fiber was efficient for solid‐phase microextraction analysis. 相似文献
1000.
Ting Hou Xiuzhong Wang Tingting Lu Xiaojuan Liu Feng Li 《Analytical and bioanalytical chemistry》2014,406(12):2943-2948
As a prominent member of the 5′-kinase family, T4 polynucleotide kinase (PNK) plays an important role in gene function regulations, and the study of PNK activity and its potential inhibitors is significant for research related to the DNA phosphorylation process. Here, we proposed a novel strategy for the detection of PNK activity and its inhibition, which combines exonuclease enzyme reaction and nicking enzyme-assisted fluorescence signal amplification. Through recycling cleavage of DNA fluorescence probe for signal amplification, a highly sensitive PNK sensing platform is developed, and a very low detection limit of 0.05 mU/mL is achieved, which is better than or comparable to that of the previously reported PNK assays. The present approach adopts a simple separation-free procedure in which the enzyme assay is conducted in homogeneous solutions. Additionally, the inhibitory effects of several known kinase inhibitors on PNK have been successfully detected. Since the proposed assay exhibits the advantages of high sensitivity and simplicity, it holds great potential in providing a promising platform for convenient and highly sensitive detection of PNK activity and its inhibitors. Figure
Schematic illustration of the strategy for sensitive PNK activity detection based on coupled lambda exonuclease reaction and nicking enzyme-assisted fluorescence signal amplification 相似文献