AbstractA mesoporous covalent triazine framework, PCPDI, was synthesized via an aromatic nitrile trimerization reaction of N,N′-di(4-cyanphenyl)- 3,4,9,10-tetracarboxydiimide (CPDI) by CF3SO3H catalyzed at 40?°C and this method avoids the use of noble metal catalyzers or high temperature reaction. PCPDI exhibits high thermal stability and strong fluorescence. The PCPDI shows ultrahigh sensitivity to tracing o-nitrophenol in chloroform with KSV constant of 1.74?×?105 L mol?1 and detection limit (LOD) of 1.72?×?10?11?mol L?1. 相似文献
Determination of the levels of 1-octacosanol is important in food stuff for the study of its pharmacological activities and health benefits. In this study, a novel, simple and fast internal standard method for the non-derivatization ultra-performance liquid chromatographic determination of 1-octacosanol in raw materials and health products was developed and validated based on evaporative light scattering detection. The linearity (r2 > 0.998), recovery (99.1–100.2%, RSD <2.7%), intra- and inter-day precision (RSD <3.8%), limit of detection (1.0 mg/L), limit of quantification (2.2 mg/L) of the 1-octacosanol were determined. The method was successfully applied to nine real 1-octacosanol products. The results of analyses had close agreement with the labeled claims of 1-octacosanol content in these products. Compared with the classical gas chromatography method, the developed method was simpler, faster and more environmentally friendly due to avoiding any derivatization step. This protocol represents a rapid and feasible method for quality control of 1-octacosanol products.
An independent set of a graph G is a set of pairwise non-adjacent vertices. Let α(G) denote the cardinality of a maximum independent set and fs(G) for 0≤s≤α(G) denote the number of independent sets of s vertices. The independence polynomial defined first by Gutman and Harary has been the focus of considerable research recently. Wingard bounded the coefficients fs(T) for trees T with n vertices: for s≥2. We generalize this result to bounds for a very large class of graphs, maximal k-degenerate graphs, a class which includes all k-trees. Additionally, we characterize all instances where our bounds are achieved, and determine exactly the independence polynomials of several classes of k-tree related graphs. Our main theorems generalize several related results known before. 相似文献
The PPh3‐catalyzed ring‐expansion reaction of sulfamate‐derived cyclic imines with acetylenedicarboxylates has been developed. The reaction works quite efficiently under very mild conditions to afford benzo[g][1,2,3]oxathiazocine‐4,5‐dicarboxylate 2,2‐dioxide derivatives in high yields. 相似文献
Organic luminescence with different forms continues to be one of the most active research fields in science and technology. Herein, an ultra-simple organic molecule (TPA-B), which exhibits both mechanoluminescence (ML) and photo-induced room-temperature phosphorescence (RTP) in the crystalline state, provides an opportunity to reveal the internal mechanism of ML and the dynamic process of photo-induced RTP in the same molecule. Through the detailed investigation of photophysical properties together with crystal structures, the key role of molecular packing and intermolecular interactions was highlighted in the luminescence response by mechanical and light stimulus, affording efficient strategies to design potential smart functional materials with multiple luminescence properties. 相似文献
A rapid and reliable method was developed and applied for the simultaneous determination of 17 organochlorine pesticides (OCPs)
in propolis. After extraction with hexane and acetone (1:1, v/v), four sorbents (florisil, silica, graphitized carbon, and
tandem graphitized carbon plus florisil) were assayed for the clean-up step. The elution solvents hexane and ethyl acetate
(1:1, v/v), hexane and dichloromethane (3:7, v/v), and ethyl acetate and hexane (2:8, v/v) were studied. The results showed
that the combination of the tandem graphitized carbon and florisil cartridge with the elution solvent of 6mL of ethyl acetate
and hexane (2:8, v/v), which was capable of eliminating matrix interference and providing colorless eluates, was the most
efficient clean-up procedure for propolis extracts when testing for OCPs. The analytical technique employed was gas chromatography
with electron capture detection (GC–ECD). The correlation coefficients from linear regression for the analyzed concentrations
(5∼100 μg/kg) were >0.9961. The limits of detection (LODs) varied between 0.8 μg/kg for 4,4′-DDE and 11.4 μg/kg for endosulfan
II, and the limits of quantitation (LOQs) ranged from 2.6 to 38.1 μg/kg. The average recoveries varied between 62.6 and 109.6%.
Relative standard deviations (RSD%) ranged from 0.8 to 9.4%. Sample analysis indicated that 4,4′-DDE was detected more often
in propolis than other pesticides, such as β-HCH, δ-HCH and heptachlor.
Figure GC-ECD chromatogram of a standard solution with 0.1 mg/L of OCPs 相似文献