Quantitative determination of Freon gas using an electronic nose

This paper reports a quantitative electronic nose (enose) for the quantitative determination of Freon gas within the concentration range 0-1000 ppm in the presence of interfering gases such as water, lubricant and petrol vapours. This quantitative enose is a new type of Freon detection system, composed of an array of four sensors. The artificial neural network (ANN) and fuzzy logic type of ANN (FNN), in combination with the relative error concept in analytical chemistry, are integrated for both quantification and discrimination. The predicted results are satisfied with a pass rate of > 80% within the permitted relative errors. The results show that the Freon enose developed in this study is reliable for both the qualitative and quantitative determination of Freon gas and exhibits the merits of high sensitivity, anti-interference and accuracy.     

Construction of a Stable Crystalline Polyimide Porous Organic Framework for C2H2/C2H4 and CO2/N2 Separation

Utilization of porous materials for gas capture and separation is a hot research topic. Removal of acetylene (C₂H₂) from ethylene (C₂H₄) is important in the oil refining and petrochemical industries, since C₂H₂ impurities deactivate the catalysts and terminate the polymerization of C₂H₄. Carbon dioxide (CO₂) emission from power plants contributes to global climate change and threatens the survival of life on this planet. Herein, 2D crystalline polyimide porous organic framework PAF-120, which was constructed by imidization of linear naphthalene-1,4,5,8-tetracarboxylic dianhydride and triangular 1,3,5-tris(4-aminophenyl)benzene, showed significant thermal and chemical stability. Low-pressure gas adsorption isotherms revealed that PAF-120 exhibits good selective adsorption of C₂H₂ over C₂H₄ and CO₂ over N₂. At 298 K and 1 bar, its C₂H₂ and CO₂ selectivities were predicted to be 4.1 and 68.7, respectively. More importantly, PAF-120 exhibits the highest selectivity for C₂H₂/C₂H₄ separation among porous organic frameworks. Thus PAF-120 could be a suitable candidate for selective separation of C₂H₂ over C₂H₄ and CO₂ over N₂.     

Carbon nanotube/poly(methyl methacrylate) composite electrode for capillary electrophoretic measurement of honokiol and magnolol in Cortex Magnoliae Officinalis

This paper describes the development and the application of a novel carbon nanotube/poly(methyl methacrylate) (CNT/PMMA) composite electrode as a sensitive amperometric detector of CE. The composite electrode was fabricated on the basis of the in situ polymerization of a mixture of CNT and prepolymerized methylmethacrylate in the microchannel of a piece of fused-silica capillary under heat. The performance of this unique system has been demonstrated by separating and detecting honokiol and magnolol in traditional Chinese medicine, Cortex Magnoliae Officinalis. Factors influencing their separation and detection processes were examined and optimized. Honokiol and magnolol were well separated within 7 min in a 40 cm long capillary at a separation voltage of 15 kV using a 50 mM borate buffer (pH 9.2). The new CNT-based CE detector offered significantly lower operating potentials, yielded substantially enhanced S/N characteristics, and exhibited resistance to surface fouling and hence enhanced stability. It demonstrated long-term stability and reproducibility with RSDs of less than 5% for the peak current (n = 9) and should also find a wide range of applications in microchip CE, flowing injection analysis, and other microfluidic analysis systems.     

Direct determination of impurities in high purity silicon carbide by inductively coupled plasma optical emission spectrometry using slurry nebulization technique

A novel method for the determination of Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni and Ti in high purity silicon carbide (SiC) using slurry introduction axial viewed inductively coupled plasma optical emission spectrometry (ICP-OES) was described. The various sizes of SiC slurry were dispersed by adding dispersant polyethylene imine (PEI). The stability of slurry was characterized by zeta potential measurement, SEM observation and signal stability testing. The optimal concentration of PEI was found to be 0.5 wt% for the SiC slurry. Analytical results of sub-μm size SiC by the slurry introduction were in good accordance with those by the alkaline fusion method which verified that determination could be calibrated by aqueous standards. For μm size SiC, results of most elements have a negative deviation and should be calibrated by the Certified Reference Material slurry. Owing to a rather low contamination in the sample preparation and stability of the slurry, the limits of detection (LODs), which are in the range of 40-2000 ng g⁻¹, superior to those of the conventional nebulization technique by ICP-OES or ICP-MS.     

Alpha‐1 antitrypsin variants in plasma from HIV‐infected patients revealed by proteomic and glycoproteomic analysis

Novel tools are necessary to explore proteins related to human immunodeficiency virus (HIV) infection. In this work, proteomic and glycoproteomic technology were employed to examine plasma samples from HIV‐positive patients. Through comparative proteome analysis of normal and HIV‐positive plasma samples, 19 differentially expressed protein spots related to 12 non‐redundant proteins were identified by ESI‐ion trap MS. Among these, the 130‐kDa isoform of α‐1‐antitrypsin was found to be decreased in HIV‐positive patients while another variant with a molecular weight of 40 kDa was increased. SWISS‐2‐D‐PAGE reference gel and protein sequence comparisons of the 40‐kDa protein showed homology with α‐1‐antitrypsin minus the N‐terminus, and its identity was further confirmed by 1‐D Western blotting and glycoproteomic analysis. In all, our results showed that proteomics and glycoproteomics are powerful tools for discovering proteins related to HIV infection. Furthermore, this 40‐kDa variant of α‐1‐antitrypsin found in the plasma of HIV‐positive individuals may prove to be a potentially useful biomarker for anti‐HIV research according to bioinformatics analysis.     

Synthesis of 3-(3-Alkyl-5-thioxo-1H-4,5-dihydro-1,2,4-triazol-4-yl)aminocarbonylchromones

A series of 3-(3-alkyl-5-thioxo-1H-4,5-dihydro-1,2,4-triazol-4-yl)aminocarbonylchromones has been prepared by oxidation of 3-formylchromone with Jones' reagent followed by reaction with 3-alkyl-4-amino-4,5-dihydro-1,2,4-triazole-5(1H)-thione in the presence of POCl³. The structures of the compounds were confirmed by IR, LC-MS, and ¹H NMR spectra and elemental analyses.     

Rapid determination of paeoniflorin and three sugars in Radix Paeoniae Alba by capillary electrophoresis.

A method based on capillary electrophoresis with electrochemical detection has been developed for the separation and determination of paeoniflorin, sucrose, glucose, and fructose in traditional Chinese medicine, Radix Paeoniae Alba. The effects of several important factors, such as the concentration of NaOH, the separation voltage, the injection time, and the detection potential, were investigated to determine the optimum conditions. The detection electrode was a 300-microm diameter copper disc electrode at a working potential of +0.60 V (versus SCE). The four analytes can be well separated within 8 min in a 40 cm length fused-silica capillary at a separation voltage of 12 kV in a 75 mM NaOH aqueous solution. The relation between the peak current and the analyte concentration was linear over about 3 orders of magnitude with detection limits (S/N = 3) ranging from 1 to 2 microM for all analytes. The proposed method has been successfully applied for the determination of the paeoniflorin and sugars in real plant samples with satisfactory assay results.     

Mesoporous silica nanoreactors for highly efficient proteolysis

Protein digestion inside the nanoreactor channels of mesoporous silica (SBA-15) is reported, and evaluated by using peptide-mass mapping. Both proteases and substrates were efficiently captured within these biocompatible nanoreactors. After 10 minutes, the mass spectrum of the protein digests released from the mesoporous-silica-based nanoreactors revealed the presence of eight peptides covering 58% of the protein sequence with an intense signal (signal/noise ratio > 70). In comparison, the conventional overnight in-solution digestion of proteins under otherwise identical conditions generated only three peptides (27% sequence coverage). We propose that this order-of-magnitude increase in the proteolytic reaction rate is mainly attributed to two factors: substrate enrichment within mesoporous silica channels and enzyme immobilization. The surface properties and macrostructure of the mesoporous silica were studied to reveal their significant influence on proteolytic reactions.     

Controlled protein assembly on a switchable surface

The strategy presented in this work supplies a general method of controlling protein assembly on a switchable low-density SAM, which may open a new way to design functional biocomposite films for biosensors or protein chips.     

糖蛋白结构质谱解析的样品前处理

基于高分辨率、高精度、高灵敏度及良好表现力的多级质谱,以标准糖蛋白辣根过