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91.
Analysis at trace levels, an ideal area of application for hyphenated techniques, is steadily gaining importance. Many sample pre-concentration and clean-up methods have been hyphenated with core analytical techniques to accomplish the task of low level detection. The present article describes the state of the art of hyphenation of various techniques such as solid phase extraction, micro-solid phase extraction, dialysis, and chromatographic modalities etc. with liquid chromatography, gas chromatography, capillary electrophoresis, and spectroscopic methods. Besides, attempts have been made to address the hyphenation approach in microfluidic devices. 相似文献
92.
Lieberzeit PA Halikias K Afzal A Dickert FL 《Analytical and bioanalytical chemistry》2008,392(7-8):1405-1410
Molecular imprinting with binary mixtures of different polycyclic aromatic hydrocarbons (PAH) is a tool for design of chemically highly sensitive layers for detection of these analytes. Sensor responses increase by one order of magnitude compared with layers imprinted with one type of template. Detection limits, e.g. for pyrene, reach down to 30 ng L(-1) in water, as could be observed with a naphthalene and pyrene-imprinted polyurethane. Comparing sensor characteristics obtained by QCM and fluorescence reveals different saturation behaviours indicating that, first, single PAH molecules occupy the interaction centres followed by gradual excimer incorporation at higher concentrations finally leading to substantial quenching, when all accessible cavities are occupied. The plateau in the mass-sensitive measurements suggests that up to 80% of the cavities generated in the MIP are re-occupied. Displacement measurements between chrysene and pyrene revealed that for imprinted layers with very high pyrene sensitivities the signals of both PAH are additive, whereas in materials with lower pyrene uptake the two analytes replace each other in the interaction sites of the polymer. 相似文献
93.
Afzal Asif Yashawantha K. M. Aslfattahi Navid Saidur R. Abdul Razak R. K. Subbiah Ram 《Journal of Thermal Analysis and Calorimetry》2021,145(4):2129-2149
Journal of Thermal Analysis and Calorimetry - Back-propagation modeling of viscosity and shear stress of Ionic-MXene nanofluid is carried out in this work. The data for Ionic-MXene nanofluid of... 相似文献
94.
Perwez Alam Nasir Ali Siddiqui Md. Tabish Rehman Afzal Hussain Ali Akhtar Showkat R. Mir Mohamed Fahad Alajmi 《Molecules (Basel, Switzerland)》2021,26(7)
Parthenolide, a strong cytotoxic compound found in different parts of Tarchonanthus camphoratus which motivated the authors to develop an optimized microwave-assisted extraction (MEA) method using Box–Behnken design (BBD) for efficient extraction of parthenolide from the stem of T. camphoratus and its validation by high-performance thin-layer chromatography (HPTLC) and cytotoxic analysis. The optimized parameters for microwave extraction were determined as: 51.5 °C extraction temperature, 50.8 min extraction time, and 211 W microwave power. A quadratic polynomial model was found the most suitable model with R2 of 0.9989 and coefficient of variation (CV) of 0.2898%. The high values of adjusted R2 (0.9974), predicted R2 (0.9945), and signal-to-noise ratio (74.23) indicated a good correlation and adequate signal, respectively. HPTLC analyzed the parthenolide (Rf = 0.16) content in T. camphoratus methanol extract (TCME) at λmax = 575 nm and found it as 0.9273% ± 0.0487% w/w, which was a higher than expected yield (0.9157% w/w). The TCME exhibited good cytotoxicity against HepG2 and MCF-7 cell lines (IC50 = 30.87 and 35.41 µg/mL, respectively), which further supported our findings of high parthenolide content in TCME. This optimized MAE method can be further applied to efficiently extract parthenolide from marketed herbal supplements containing different Tarconanthus species. 相似文献
95.
Nisar Jan Nasir Umar Ali Ghulam Shah Afzal Farooqi Zahoor Hussain Iqbal Munawar Shah Muhammad Raza 《Cellulose (London, England)》2021,28(12):7593-7607
Cellulose - In this work we have attempted to use biomass as energy source which is abundantly available throughout the world. The work is focused on pyrolysis of sugarcane bagasse in a... 相似文献
96.
Yanhui Zhang Hao Teng Ying Gao Muhammad Wasim Afzal Jingye Tian Xi Chen Haoyang Tang Tony D. James Yuan Guo 《中国化学快报》2021,31(11):2917-2920
Triazolopyridines are an important kind of fused-ring compounds. A HOCl-promoted triazolopyridine formation strategy is reported here for the first time in which hypochlorous acid (HOCl) mildly and efficiently promotes the formation of 1,2,4-triazolo[4,3-a]pyridines NT1-NT6 from various 2-pyridylhydrazones N1-N6. N6, a rhodol-pyridylhydrazone hybrid, was developed into a fluorescent probe for the selective detection of HOCl, and successfully applied to probe endogenous HOCl in living cells and zebrafish in situ and in real time. The present intramolecular cyclization reaction is selective and atom-economical, thereby not only providing an important approach for the convenient synthesis of triazolopyridines, but also offering a general strategy for sensitive, selective and biocompatible detection of endogenous HOCl in complex biosystems. 相似文献
97.
The stress-induced phase transformation characteristics of unirradiated and proton beam irradiated NiTi alloy were investigated at different tests temperatures. The wire-shaped NiTi specimens were irradiated by 2?MeV proton beam for 30?min at room temperature to a flux of 1019 protons/m2 s. Engineering stress–strain (S-S) curves of both unirradiated and irradiated specimens were obtained using a materials testing machine at 25, 50, 75 and 100°C. The results indicate a single-stage phase transformation from austenite to martensite (B2–B19′) in unirraidated specimens at all the test temperatures. In contrast, in the case of the irradiated specimens, a two-stage austenite–rhombohedral–martensite (B2–R–B19′) phase transformation is observed at 25 and 50°C. The B2–R–B19′ phase transformation, however, is found to change into B2–B19′ transformation at 75 and 100°C. The stress required to initiate the B19′ phase transformation (σMS) and the plateau range are found to be lower in irradiated specimens compared with those of the unirradiated specimens. The results obtained are discussed on the basis of the formation of Ni4Ti3 precipitates in irradiated specimens and their consequences on the phase transformations. 相似文献
98.
Sartaj Tabassum Waddhaah M. Al–Asbahy Mohd. Afzal Manal shamsi Farukh Arjmand 《Journal of luminescence》2012,132(11):3058-3065
Synthesis, characterization, DNA binding and cleavage studies of [Zn(glygly)(ssz)(H2O)]·6H2O (1) containing glycyl glycine and sulfasalazine ligand. Complex 1 recognize minor groove of DNA and show hydrolytic DNA cleavage.Highlights? Novel Zn(II) complex 1 bearing bioactive glycyl glycine and sulfasalazine ligand scaffold. ? Cleavage activity of 1 was enhanced in presence of activators: H2O2>MPA>GSH>Asc. ? Complex 1 recognize minor groove as depicted in the cleavage pattern and molecular docking. ? Complex 1 cleaves pBR322 DNA via hydrolytic mechanism and validated by T4 DNA ligase experiments. 相似文献
99.
Computational meshes for numerical simulation frequently show—at least locally—a structure resembling a triangulated grid. Our goal is to recognize product-like structures in triangular meshes. We define triangulated Cartesian products of graphs and analyze their structural properties. We show how to recognize and factorize graphs that are triangulated products of two factors, when the factors are triangle-free graphs. We also discuss properties of products with more than two factors. 相似文献
100.
Zia‐ur‐Rehman Niaz Muhammad Afzal Shah Saqib Ali Ezzat Khan 《Heteroatom Chemistry》2012,23(6):560-567
Four triorganotin derivatives of general formula C10H10NS2SnR3,, where R = CH3 ( 1 ), C4H9 ( 2 ), C6H11 ( 3 ), and C6H5 ( 4 ), have been synthesized by the metathesis reaction of 1,2,3,4‐tetrahydroisoquinolnium salt of ligand with triorganotin(IV) chloride in the 1:1 ratio. These complexes were characterized by elemental analysis, Raman, IR, multinuclear NMR (1H, 13C, and 119Sn), and mass spectrometry. The crystal structure confirmed a supramolecular zig‐zag chain structure mediated by S–H (2.968 Å) for complex 4 with the central Sn atom exists in a distorted trigonal bipyramidal geometry. A subsequent antibacterial study indicates that the compounds are biologically active. 相似文献