Construction of amine-rich coating utilizing amine curing reaction of triglycidyl isocyanate with triethylenetetramine on the surface of poly(styrene-divinylbenzene) microspheres for preparation of anion exchange stationary phase.

Epoxy resins, as important thermosetting polymers, exhibit excellent adhesion to various substrates. In view of this, reticulate coating of triglycidyl isocyanate with triethylenetetramine was introduced onto the surface of poly(styrene-divinylbenzene) utilizing amine curing reaction to obtain poly(styrene-divinylbenzene)@triglycidyl isocyanate-triethylenetetramine composite microspheres. The amino groups and epoxy groups of triglycidyl isocyanate-triethylenetetramine endowed poly(styrene-divinylbenzene) with good reactivity, which could be quaternized under mild conditions to obtain an anion exchange chromatographic stationary phase. The quaternized poly(styrene-divinylbenzene)@triglycidyl isocyanate-triethylenetetramine was characterized by scanning electron microscope, Fourier-transform infrared spectroscopy, N2 adsorption-desorption experiment, et al. The chromatographic performance of the customized column was evaluated by separating seven conventional anions, organic weak acids, and carbohydrates. Poly(styrene-divinylbenzene)@triglycidyl isocyanate-triethylenetetramine possesses the uniform size of poly(styrene-divinylbenzene) microspheres and good reactivity of triglycidyl isocyanate-triethylenetetramine, which offers a flexible strategy for the preparation of anion exchange stationary phase. The column exhibits excellent chemical and mechanical stability and chromatographic performance. Finally, the column was successfully applied for the determination of nitrite in pickles.

Improving Triethylamine-Sensing Performance of WO3 Nanoplates through In Situ Heterojunction Construction.

Surface engineering techniques can be used to develop high-performance gas sensing materials and advance the development of sensors. In this study, we improved the gas sensing performance of two-dimensional (2D) WO3 nanoplates by combining surface Zn modification and the in situ formation of ZnWO4/WO3 heterojunctions. Introducing Zn atoms by surface modification can reconstruct the atomic surface of 2D WO3 nanoplates, creating additional active sites. This allowed for the preparation of various types of ZnWO4/WO3 heterojunctions on the surface of the WO3 nanoplates, which improved the selectivity and sensitivity to the target gas triethylamine. The sensor exhibited good gas sensing performance for triethylamine even at low operating temperatures and strongly resisted humidity changes. The ZnWO4/WO3 material we prepared demonstrated a nearly threefold improvement in the triethylamine (TEA) response, with a gas sensing responsivity of 40.75 for 10 ppm of TEA at 250 °C. The sensor based on ZnWO4/WO3 has a limit of detection (LOD) for TEA of 200 ppb in practical measurements (its theoretical LOD is even as low as 31 ppb). The method of growing ZnWO4 on the surface of WO3 nanoplates using surface modification techniques to form surface heterojunctions differs from ordinary composites. The results suggest that the in situ construction of surface heterojunctions using surface engineering strategies, such as in situ modifying, is a practical approach to enhance the gas sensing properties and resistance to the humidity changes of metal oxide materials.

Determination and comparison of agarwood from different origins by comprehensive two-dimensional gas chromatography-quadrupole time-of-flight mass spectrometry.

Agarwood, a species of resinous heartwood, is a precious medicinal plant and a type of rare natural spice, which is widely used in medicine, cosmetics, religious activities, and other fields. In this study, agarwood samples from eight different regions across four countries were analyzed by comprehensive two-dimensional gas chromatography-quadrupole time-of-flight mass spectrometry. A total of 232 species were identified (the match factors of these compounds were above 750). The main compounds of agarwood are oxygenated sesquiterpenes and chromones. The compositions of India1 and Malaysia2 were significantly different from those of other samples, which might be attributed to the different production processes of agarwood. For further investigation, factor analysis was conducted for six agarwood samples. The results showed that the data classification possessed a regional characteristic; according to the retention time and relative content, characteristic compositions were determined by factor scores. Finally, the differences of characteristic compositions were simply analyzed, and the reasons were speculated.

Silver Nanoparticles-Decorating Manganese Oxide Hybrid Nanostructures for Supercapacitor Applications.

A facile aerosol-based synthetic approach is demonstrated for the fabrication of silver-manganese oxide (Ag-MnOx) and cetyltrimethylammonium bromide (CTAB)-templated silver-manganese oxide (c-Ag-MnOx) hybrid nanostructures as the positive electrode materials of supercapacitors. Through gas-phase evaporation-induced self-assembly, silver nanoparticles are homogeneously decorated in the hybrid nanostructure to create a conductive path at the interface of the cluster of MnOx crystallites. The utilization of the capacitance of MnOx increases by the addition of Ag nanoparticles (>2 times for Ag-MnOx and ∼1.7 times for c-Ag-MnOx). An optimal specific capacitance is achieved when the concentration of the silver precursor (CAg) is 0.5 wt %, 118 F g-1 for Ag-MnOx, and 154 F g-1 for c-Ag-MnOx at a specific current of 1 A g-1. The enhanced supercapacitive performance by the addition of CTAB at low CAg is attributed to the increased surface area (>19.4%) for electrochemical reactions. The prototype method with mechanistic understanding demonstrated in this study shows promise for the fabrication of a variety of MnOx-based hybrid nanostructures for supercapacitor applications.

Adaptive kernel independent component analysis and UV spectrometry applied to characterize the procedure for processing prepared rhubarb roots.

By determination of the number of absorptive chemical components (ACCs) in mixtures using median absolute deviation (MAD) analysis and extraction of spectral profiles of ACCs using kernel independent component analysis (KICA), an adaptive KICA (AKICA) algorithm was proposed. The proposed AKICA algorithm was used to characterize the procedure for processing prepared rhubarb roots by resolution of the measured mixed raw UV spectra of the rhubarb samples that were collected at different steaming intervals. The results show that the spectral features of ACCs in the mixtures can be directly estimated without chemical and physical pre-separation and other prior information. The estimated three independent components (ICs) represent different chemical components in the mixtures, which are mainly polysaccharides (IC1), tannin (IC2), and anthraquinone glycosides (IC3). The variations of the relative concentrations of the ICs can account for the chemical and physical changes during the processing procedure: IC1 increases significantly before the first 5 h, and is nearly invariant after 6 h; IC2 has no significant changes or is slightly decreased during the processing procedure; IC3 decreases significantly before the first 5 h and decreases slightly after 6 h. The changes of IC1 can explain why the colour became black and darkened during the processing procedure, and the changes of IC3 can explain why the processing procedure can reduce the bitter and dry taste of the rhubarb roots. The endpoint of the processing procedure can be determined as 5-6 h, when the increasing or decreasing trends of the estimated ICs are insignificant. The AKICA-UV method provides an alternative approach for the characterization of the processing procedure of rhubarb roots preparation, and provides a novel way for determination of the endpoint of the traditional Chinese medicine (TCM) processing procedure by inspection of the change trends of the ICs.

[Extraction of spectral information of additives from activated manganese dioxide products using adaptive kernel independent component analysis].

The additives were abstracted from the manganese dioxide products with four kinds of organic solvents, ether, acetone, chloroform and toluene. The extracts were then baked and their attenuated total reflectance (ATR) FTIR spectra were measured using liquid membrane method. The number of chemical components of the additives was determined by median absolute deviation (MAD), and the spectral information of the pure component was extracted by kernel independent component analysis (KICA). The extracted spectral information of the additives is accordant to that of the practically used compounds. An adaptive kernel independent component analysis (AKICA) was proposed for directive extraction of spectral information from chemical mixtures. The results demonstrated that the AKICA method provides an alternative approach to extracting spectral information from the chemical mixtures without previously chemical or physical preseparation for direct extracting spectral information of pure components in the mixed system.

[Determination of trace elements in tobaccos by microwave digestion/ICP-MS method].

2 mL 50% HNO3 and 1 mL 47% H2O2 were chosen for tobaccos digestion, and the acidity of final digestion solution was confined to about 2%. Standard solutions were diluted with 2% HNO3. The digestion solutions were determined by ICP-MS directly after adding internal standard elements Ge and Rh. In stead of using concentrated acid, this method not only can leave out the process of drying or dilution and extended the life of relevant components of the instrument, but also eliminate the errors of the inconsistency between digestion solutions and standard solutions could be eliminated. The contents of 30 trace elements, the results of eight representatives of which were provided, in tobaccos from seven areas were determined. The detection limits of measured elements were from 0.006 to 1.133 ng x mL(-1). The relative standard deviations were from 0.90% to 5.66%. The recovery rates of two elements (Cu, Y) were from 93% to 102%. The results showed that this method proposed could be applied to multielement simultaneous determination of tobaccos, and there is a deep relationship between the contents of the trace elements and the production place and classification of tobaccos.

[Preparation and characterization of polyaniline/graphene-coated anion-exchange chromatographic stationary phase].

A polyaniline/graphene (PANI/G) composite was selected as the coating material to prepare a coated anion-exchange chromatographic stationary phase. First, aniline and graphene were used to prepare the PANI/G composite, which was coated onto the surface of poly(styrene-divinylbenzene) (PS-DVB) microspheres by physical absorption. Then, a series of anion-exchange stationary phases with different exchange capacities were obtained by quaternization using the nitrogen atom of polyaniline as the reactive site. The stationary phase was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and elemental analysis (EA). The results revealed that PANI/G was successfully coated onto the surface of PS-DVB and quaternized. The efficiency of the self-fabricated chromatographic column was evaluated by separating conventional anions and organic acids. The PANI/G-coated PS-DVB anion-exchange chromatographic column that was quaternized eight times showed good separation performance for conventional anions and organic acids.

Determination of behavior of catalpol hexapropionate in simulated gastric conditions by UPLC-ESI-HRMS.

Catalpol hexapropionate (CP-6) was designed and synthesized as anti-aging drug. In order to investigate the behavior of CP-6 in simulated gastric juice, ultra-high performance liquid chromatography-electrospray ionization-high resolution mass spectrometry was used to determinate the components produced in simulated gastric conditions. Six metabolites were identified with the possible metabolic processes proposed. Hydrolysis may be the main metabolic pathways. The relative contents of CP-6 and its metabolites were determined using their extractive ion chromatograms. The results show that the relative content of CP-6 is rapidly decreased about 15% during the first 0.5 h and generally stable after 0.5 h. The mainly produced metabolites are catalpol penta-propionate (CP-5), catalpol and a spot of catalpol tetra-propionate (CP-4), catalpol tri-propionate (CP-3), catalpol dipropionate (CP-2) and catalpol propionate (CP-1). The metabolitic process of CP-6 may be an hydrolysis under acid conditions. The research results can provide useful information for development and utilization of CP-6 as a pharmaceutical preparation.

Characterization of radix rehmanniae processing procedure using FT-IR spectroscopy through nonnegative independent component analysis.

A method is proposed for monitoring the radix rehmanniae proparate processing procedure and determining the endpoint of the process using attenuated total reflectance (ATR) FT-IR through nonnegative independent component analysis (ICA). In the proposed method, ATR FT-IR spectra of the samples were firstly measured at different steaming periods. Then, nonnegative ICA was used for direct estimation of the feature spectra of the pure components in the mixture without pre-separation and other prior information. The estimated independent components (ICs) and their variation of the relative concentrations were used to characterize the processing procedure and determine the endpoint. The results show that the estimated three ICs are consistent with that of the chemical components in the mixtures, i.e. catalpol/rehmaionoside, glucose, and other compounds that nearly keep invariant during the processing procedure. The endpoint determined by the IR-ICA method is 15 h, which was located in the range obtained by expert sensory analysis, whereas the endpoint determined by the traditional sensory analysis is 14-17 h and even 14-20 h, which showed the significant deviation of the endpoints determined by different operators.

[Determination and comparison of metal elements in Huai radix rehmanniae at different grades by ICP-MS].

The Huai radix rehmanniae at different grades was pretreated by wet digestion, and then the metal elements in the radix rehmanniae and the prepared sample by steaming method were determined using ICP-MS. The results indicate that there is no obvious difference in the metal elements between the different grades and between the dried radix rehmanniae and its corresponding prepared product. There are elements Zn, Cu, Cr, Fe, Mn, Sn, Ni, Mo, Go, etc. in radix rehmanniae, among which the contents of Ca, Fe, Al, Zn and Cu are higher; the metal elements beneficial to human body in dried radix rehmanniae are relative lower than that in the prepared one. The elements such as Co, Ni, Cr, Mn, etc. in radix rehmanniae have poison effects on human body when their contents are more than a certain threshold value, although they are human essential elements. Element Pb is harmful to human body, which should be controlled and reduced/eliminated in the processing procedure. The determination and comparison of the metal elements in radix rehmanniae at different grades can provide useful information about the comprehensive evaluation of dried radix rehmanniae and their prepared products.

[Theoretical study on infrared vibration spectrum of catalpol by DFT].

The catalpol, which can be isolated from the Chinese traditional herbs Rehmannia glutinosa as an effective and active ingredient, is an iridoid glycoside with many pharmacological functions. The molecular structure and the infrared (IR) spectrum of catalpol were calculated using density-functional theory (B3LYP) at 6-311G** level, and the theoretical frequency was scaled by 0. 96. The vibrational modes of IR spectrum were assigned and compared with that of the experimental data. The calculated IR spectral features from DFT are in good agreement with the experimental ones. The results indicate that DFT is an useful method for the structure optimization and IR spectrum calculation of the iridoid compounds, which can be isolated from natural resources and often with difficulty. The theoretical calculation results of IR spectrum can provide useful information for the prediction of the theoretical property and investigation of the structure-activity relationship of the iridoid compounds.

Fabrication of monodisperse poly (allyl glycidyl ether-co-divinyl benzene) microspheres and their application in anion-exchange stationary phase.

Micron-sized poly (allyl glycidyl ether-co-divinyl benzene) microspheres were prepared by a seed swelling and polymerization method and applied to prepare anion-exchange stationary phases by direct quaternization. The mono-dispersity, diameters, surface characteristics and porosity of microspheres were measured by scanning electron microscope and nitrogen adsorption-desorption measurements. The anion-exchange stationary phases were characterized by Fourier Transform Infrared Spectrum, Elemental Analysis, Breakthrough Curve, etc. The chromatographic properties of this self-fabricated anion-exchange column were investigated by separating conventional anions and organic weak acids. According to the results, poly (allyl glycidyl ether-co-divinyl benzene) microsphere possesses good compatibility in the whole pH range of 1-14; the presence of epoxy group guarantees the microsphere's superior reaction activity. The prepared poly (allyl glycidyl ether-co-divinyl benzene) microsphere is promising to replace poly (styrene-divinylbenzene) and poly (glycidylmethacrylate-divinylbenzene) and becomes a generation of support for the preparation of anion exchangers.

Characterization of volatile components in dry chrysanthemum flowers using headspace-liquid-phase microextraction-gas chromatography.

A headspace-liquid-phase microextraction (HS-LPME)-GC (gas chromatography) method for the characterization of volatile components in dry chrysanthemum flowers has been developed. In the proposed method, two extraction solvents, n-hexadecane and benzyl alcohol, are used for preconcentrating volatiles in the sample. A droplet of the extraction solvent is squeezed from the GC syringe and inserted in the headspace of the sample bottle with the dry flower, immersed in deionized water, and warmed in a water bath. The optimum HS-LPME parameters in terms of extraction solvent type, droplet magnitude, equilibrium (water bath) temperature, equilibrium time, extraction time, and ionic strength are achieved using GC-FID (flame ionization detection) by varying several levels of the factors that affect the HS-LPME procedure. After extraction under the optimized conditions, the extraction droplet is retracted into the syringe and injected for GC-MS (mass spectrometry) analysis. Thirty-three volatile components are extracted and identified using this HS-LPME-GC-MS method, with the aid of chemometric methods. It is shown that the volatiles in dry chrysanthemum flowers are mainly unsaturated organic compounds, such as monoterpenes, sesquiterpenes and their oxygenous derivatives, triterpenoids, and aliphatic compounds. Several representative components, in order of precedence of the retention time, are pinene (106.3 microg/g), camphene (112.7 microg/g), eucapyptol (52.1 microg/g), camphor (29.4 microg/g), borneol (4.2 microg g), bornyl acetate (67.3 microg/g), caryophyllene (0.7 microg/g), and caryophyllene oxide (20.0 microg/g). The relative standard error and detection limit of this method is 5-9% and 0.4 microg/g, respectively.

Estimation of source infrared spectra profiles of acetylspiramycin active components from troches using kernel independent component analysis.

Kernel independent component analysis (KICA), a kind of independent component analysis (ICA) algorithms based on kernel, was preliminarily investigated for blind source separation (BSS) of source spectra profiles from troches. The robustness of different ICA algorithms (KICA, FastICA and Infomax) was first checked by using them in the retrieval of source infrared (IR), ultraviolet (UV) and mass spectra (MS) from synthetic mixtures. It was found that KICA is the most robust method for retrieval of source spectra profiles. KICA algorithm is subsequently adopted in the analysis of diffuse reflection IR of acetylspiramycin (ASPM) troches. It is observed that KICA is able to isolate the theoretically predicted spectral features corresponding to the ASPM active components, excipients and other minor components as different independent (spectral) component. A troche can be authenticated and semi-quantified using the estimated ICs. KICA is an useful method for estimation of source spectral features of molecules with different geometry and stoichiometry, while features belonging to very similar molecules remain grouped.

[Preparation and characterization of a latex-agglomerated anion exchange chromatographic stationary phase].

Allyl glycidyl ether (AGE) was selected as the copolymerization monomer to prepare a copolymer latex-agglomerated anion exchange chromatography stationary phase for ion chromatography (IC). First, allyl glycidyl ether-styrene (AGE-ST) copolymer latex was prepared by the saponification emulsion polymerization method. It was then quaternized by reacting alternatively with methylamine (MA) and 1,4-butanedioldiglycidyl ether (BDDGE) and agglomerated on the surface of sulfonated polystyrene-divinylbenzene (PS-DVB) microspheres to obtain a copolymer latex-agglomerated anion exchange chromatography stationary phase. The stationary phase was characterized by scanning electron microscopy (SEM), FT-IR and elemental analysis (EA). It was found that the diameters of the PS-DVB microsphere and AGE-ST copolymer latex were about 6 µm and 300 nm, respectively. The quaternized AGE-ST copolymer latex was successfully agglomerated on the surface of PS-DVB microspheres and the nitrogen content increased as quaternization time was increased. The chromatographic properties were evaluated by separating conventional anions and organic acids. The results showed that the quaternized AGE-ST copolymer latex-agglomerated PS-DVB anion exchange column exhibited good separation properties toward anions. Therefore, based on the good pH toleration and reaction activity of the newly developed stationary phase, it was concluded that using AGE as a monomer was a good choice.

Determination of γ-hydroxybutyrate in human urine samples by ion exclusion and ion exchange two-dimensional chromatography system.

A two-dimensional ion chromatography system was developed for the determination of γ-hydroxybutyrate (GHB) in human urine samples. Ion exclusion chromatography was used in the first dimensional separation for elimination of urine matrices and detection of GHB above 10mgL-1, ion exchange chromatography was used in the second dimensional separation via column-switching technique for detection of GHB above 0.08mgL-1. Under the optimized chromatographic conditions, the ion exclusion and ion exchange chromatography separation system exhibited satisfactory repeatability (RSD<3.1%, n=6) and good linearity in the range of 50-1000mgL-1 and 0.5-100mgL-1, respectively. By this method, concentrations of GHB in the selected human urine samples were detected in the range of 0-1.57mgL-1. The urine sample containing 0.89mgL-1 GHB was selected to evaluate the accuracy; the spiked recoveries of GHB were 95.9-102.8%. The results showed that the two-dimensional ion chromatography system was convenient and practical for the determination of GHB in human urine samples.

Investigation of pyrolysis behavior of carbofuran by pyrolysis-gas chromatography-mass spectrometry.

Carbofuran is a kind of carbamate pesticide commonly used on major crops. For understanding of the composition variation versus temperature and pyrolysis mechanism, its pyrolysis behavior was simulated and investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The pyrolysates were directly injected for GC-MS analysis. Totally 86 components were determined based on mass spectra library matching with the aid of the correlation of boiling point (bp) and retention time. It was found that carbofuran was obviously decomposed with the temperature increase. A large number of mono aromatics and polycyclic aromatic hydrocarbons (PAHs) were formed when the temperature was higher than 750 degrees C, and the higher was the temperature, the more was the content of the corresponding aromatic hydrocarbon. Besides the aromatic hydrocarbons, there were oxygenous and/or nitrogenous compounds produced in the pyrolysis process. Furthermore, the pyrolysis mechanism of carbofuran was proposed based on the determined pyrolysates and their contents variation versus the temperature. The investigation results can provide the useful information for understanding of the thermal behavior of carbofuran and evaluation of the potential influence of the pyrolysates to living thing and the environment.

Determination and characterization of the pyrolysis products of isoprocarb by GC-MS.

The pyrolysis behavior of isoprocarb (an insecticide with contact and stomach action) is investigated using pyrolysis-gas chromatography-mass spectrometry. The pyrolysis products are separated using an HP-5 column under temperature program with helium as the carrier gas. The total of 80 separated pyrolysis components at 600 degrees C, 750 degrees C, and 900 degrees C under helium atmosphere are identified using a probability-based matching search procedure, combined with the correlation of boiling point (BP) and Lee retention index (RI). Some of the BP values of the tentative components are estimated using the group contributions method because experimental values are not available. The levels of the identified components are estimated by the peak area normalization method from the chromatogram. It is found that isoprocarb decomposes more with the increase of temperature, and a large number of mono aromatics and polycyclic aromatic hydrocarbons and their derivatives are produced when the pyrolysis temperature is higher than 750 degrees C. The content of the decomposition products in the pyrolysate varies from 0.04% to 22.20%.

Characterization of the thermal decomposition and polymerization of arprocarb using pyrolysis-GC-MS.

Arprocarb is a carbamate type insecticide used to control cockroaches, flies, mosquitoes, and is a lawn and turf insect growth regulator. In order to evaluate the effects of the thermal behavior of arprocarb on its bioactivity or the environment, its thermal decomposition and polymerization were characterized using pyrolysis-GC-MS (Py-GC-MS). Arprocarb was pyrolysed at 450 degrees C, 600 degrees C, 750 degrees C, and 900 degrees C, respectively. In all 71 components were determined. It was found that arprocarb was obviously decomposed when the temperature was lower (450 approximately 750 degrees qC), and a large number of mono- and polycyclic aromatic hydrocarbons (PAHs) were produced at higher temperatures (750 approximately 900 degrees C). Furthermore, the variety of the representative compounds versus the temperature was reported. The research results can provide useful information for the understanding of the thermal behavior of arprocarb.