Thermal, spectral and AFM studies of calcium silicate hydrate-polymer nanocomposite material

A non-ionic polymer (poly(vinyl alcohol) (PVA)) has been incorporated into the inorganic layers of calcium silicate hydrate (C–S–H) during precipitation of quasicrystalline C–S–H from aqueous solution. C–S–H and a C–S–H-polymer nanocomposite (C–S–HPN) material were synthesized and characterized by X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), ²⁹Si magic angle spinning nuclear magnetic resonance (²⁹Si MAS NMR) and ¹³C cross-polarization nuclear magnetic resonance (¹³C CP NMR) spectroscopy, atomic force microscopy (AFM), thermal conductivity, thermogravimetric analysis (TG) and differential thermal analysis (DTA). Thermal conductivity of PVA, C–S–H and C–S–HPN material was studied in the temperature range 25–50°C. C–S–HPN materials exhibited the highest thermal conductivity at 25 and 50°C. The thermal conductivity increases from 25 to 50°C are 7.03, 17.46 and 14.85% for PVA, C–S–H and C–S–HPN material, respectively. Three significant decomposition temperature ranges were observed on the TG curve of C–S–HPN material.     

An improved version of Junmeng–Fang–Weiming–Fusheng approximation for the temperature integral

An improved version of Junmeng–Fang–Weiming–Fusheng approximation for the temperature integral has been developed. The accuracy of the improved approximation for the temperature integral has been tested by some numerical analyses. The systematic analysis of the relative errors involved in the kinetic parameters obtained from Junmeng–Fang–Weiming–Fusheng integral method and its improved version has been also carried out. The results have shown that the improved approximation is more accurate than Junmeng–Fang–Weiming–Fusheng approximation as the solution of the temperature integral, and that more accurate kinetic parameters can be determined from the integral method based on the improved temperature integral approximation.     

Slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of Cr, Cd and Pb in plastics

Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cell inductively coupled plasma mass spectrometry (USS–ETV–DRC–ICP–MS) for the determination of Cr, Cd and Pb in several plastic samples, using NH₄NO₃ as the modifier, is described. The influences of the instrumental operating conditions and the slurry preparation technique on the ion signals are investigated. A reduction in the intensity of the background at signals corresponding to chromium masses (arising from matrix elements) was achieved by using NH₃ as the reaction cell gas in the DRC. The method was applied to determine Cr, Cd and Pb in two polystyrene (PS) samples and a polyvinyl chloride (PVC) sample using two different calibration methods, namely standard addition and isotope dilution. The results were in good agreement with those for digested samples analyzed by ultrasonic nebulization DRC–ICP–MS. The precision between sample replicates was better than 17% with the USS–ETV–DRC–ICP–MS method. The method detection limits, estimated from standard addition curves, were about 6–9, 1–2 and 8–11 ng g⁻¹ for Cr, Cd and Pb, respectively, in the original plastic samples.     

Transfer Volumes of Glycine, L–Alanine, and L–Serine from Water to 1,2-Butanediol–Water Mixtures at 298.15 K

Densities of solutions of glycine, L–alanine, and L–serine have been measured by an oscillating-tube densimeter in 1,2-butanediol–water mixtures with 1,2-butanediol mass fractions ranging from 0 to 0.35 at 298.15 K. Apparent molar volumes and limiting partial molar volumes of each amino acid have been used to obtain the corresponding transfer volumes from water to different concentrations of 1,2-butanediol–water mixtures. The transfer volumes are positive for glycine and L–serine, and both positive and negative for L–alanine over the concentration range studied. The results are interpreted in terms of solute–solvent interactions. Substituent effects are also discussed.     

Simultaneous GC-MS quantitation of acids and sugars in the hydrolyzates of immunostimulant, water-soluble polysaccharides of basidiomycetes

Summary The simultaneous quantitation of acids and sugars as their trimethyl silyl (TMS) derivatives has been extended in order to identify and quantitate the simple acid and sugar constituents in the hydrolyzates of various immunostimulant, water-soluble polysaccharides obtained from various Basidiomycetes, such as Armillariella mellea, Auricularia auricula-judae, Coriolus versicolor, Flammulina velutipes, Fomes fomentarius, Ganoderma applanatum, Ganoderma lucidum, Pleurotus ostreatus, Schizophyllum commune, Trametes hirsuta. Optimum hydrolysis conditions, performed with 2 M trifluoroacetic acid (TFAA) for five hrs, proved the presence of several sugars and acids with maximum recovery. (i) the total sugar/sugar alcohol content of polysaccharides varied between 20- and 65% and consisted of arabitol (0.01–10.2%), arabinose (0.09–1.3%), ribose (0.2–1.8%), fucose (0.3–1.2%), mannitol (0.01–5.3%), sorbitol (0.01–0.05%), galactiol (0.04%), fructose (0.08–0.8%), galactose (0.9–29%), glucose (10–53%), uronic acids (0.14–3.7%), sucrose (0.03–2%), trehalose (0.2–1%), cellobiose (0.01–0.6%), maltose (0.2–1.9%), other disaccharides (0.2–8%). (ii) The total of acids varied from 1.5 to 30% including o-phosphoric (1.3–19%), malic (0.08–4.7%), citric (0.08–4.7%), isocitric; (3%) and C₁₆−C₁₈ fatty acids (1–6%).     

Properties of Zinc alloy electrodeposits produced from acid and alkaline electrolytes

Zinc–cobalt (Zn–Co) and zinc–nickel (Zn–Ni) alloy electrodeposits each prepared from acid and alkaline formulations were compared for their properties. Compared to alkaline baths, acid baths offer higher metal percent of the alloying element and higher current efficiency. In alkaline baths, the variation of metal percent in deposit with current density is less significant, but that of current efficiency with current density is more. Electrolyte pH does not change significantly in alkaline solutions compared to acid solutions. X-ray diffraction evaluation of Zn–Co deposits from both electrolytes indicated their presence in the η-phase, while Zn–Ni shows pure γ-phase for deposits obtained from alkaline solutions and the existence of γ-phase with traces of η-phase of zinc for deposits obtained from the acid electrolytes. Scanning electron microscope examination shows finer grain structure for deposits obtained from alkaline solutions, and atomic force microscope studies confirm their nanostructure with reduced surface roughness. Deposits obtained from the alkaline baths exhibited higher corrosion resistance probably due to their nanostructure.     

Selective extraction of sulfonamides from food by use of silica-coated molecularly imprinted polymer nanospheres

We report the use of nanospheres prepared by coating silica with molecularly imprinted polymer (MIP) for sulfamethoxazole (SMO). The resulting SiO₂–SMO–MIP nanoparticles have highly improved imprinting and adsorption capacity, and can be used for separation and determination of sulfonamides in eggs and milk. In the synthesis, monodispersed SiO₂ nanoparticles (Si–NP) of diameter 80 nm were amino-modified by reaction with 3-aminopropyltriethoxylsilane. The acryloyl monolayer was then grafted onto the amine-modified Si–NP. Finally, the MIP films were coated on to the surface of Si–NP by the copolymerization of the vinyl end groups with functional monomer (acrylamide), cross-linking agent (ethylene glycol dimethacrylate), initiator (azo-bis-isobutyronitrile), and template molecule (sulfamethoxazole). The resulting SiO₂–SMO–MIP–NP were characterized by transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectrometry. The adsorption properties were demonstrated by equilibrium rebinding experiments and Scatchard analysis. The results showed that the binding sites of the SiO₂–SMO–MIP were highly accessible, and the maximum adsorption capacity of the SiO₂–SMO–MIP for SMO was 20.21 mg g⁻¹. The selectivity of the SiO₂–SMO–MIP–NP obtained was elucidated by using SMO and structurally related sulfonamides. The results indicated that the SiO₂–SMO–MIP had significant selectivity for SMO. The feasibility of removing SMO and sulfadiazine (SDZ) from food samples was proved by use of spiked milk and eggs. A method for the separation and determination of trace SMO and SDZ in milk and egg samples was developed, with recoveries ranging from 69.8% to 89.1%.     

Thermal decomposition properties of 1,2,4-triazole-3-one and guanidine nitrate mixtures

1,2,4-triazole-3-one (TO) and guanidine nitrate (GN) have the potential to be used as alternative gas-generating agents. To obtain a better understanding of thermal decomposition properties of TO/GN mixtures, sealed cell differential scanning calorimetry, thermogravimetry–differential thermal analysis–infrared spectroscopy (TG–DTA–IR), and thermogravimetry–differential thermal analysis–mass spectrometry (TG–DTA–MS) were carried out. The endothermic peak and onset temperatures of TO/GN mixtures were lower than those of individual TO and GN. TG–DTA–IR and TG–DTA–MS showed that the mass of TO/GN mixtures decreased with heat generation and N₂ evolved as the major gas during thermal decomposition. The interaction between TO and nitric acid from the dissociation of GN is proposed for the thermal decomposition of TO/GN mixtures.     

Interactions of Tetrakis(4-sulfonatophenyl)porphyrin with γ-Cyclodextrin and Alkyltrimethylammonium Bromides in Aqueous Solutions

Tetrakis(4-sulfonatophenyl)porphyrin (TSPP) forms complexes with octyltrimethylammonium bromide (OTMA) and hexyltrimethylammonium bromide (HTMA) in pH 7.3 buffers. At low concentrations of OTMA (HTMA), a 1:1 TSPP–OTMA complex is formed. As the OTMA (HTMA) concentration is increased, a 1:2 TSPP–OTMA (HTMA) complex is also formed. The equilibrium constants for the formation of the TSPP–OTMA (HTMA) complexes have been evaluated from a simulation of the observed fluorescence intensity data. In the induced circular dichroism spectrum, the signal intensity of TSPP in aqueous solutions containing both γ-CD and OTMA has been similar to that containing only γ-CD, suggesting the formation of the 1:1:1 γ-CD–TSPP–OTMA (HTMA) inclusion complex. Capillary electrophoretic study has exhibited the formation of the 1:1 TSPP–OTMA (HTMA) complex, although the 1:2 TSPP–OTMA (HTMA) complex could not be observed, probably because the OTMA (HTMA) concentration used was low. The equilibrium constants for these 1:1 complexes have been evaluated from the variation in the electrophoretic mobility. The equilibrium constant for the formation of the 1:1:1 γ-CD–TSPP–OTMA or γ-CD–TSPP–HTMA complex has been evaluated from a simulation of the electrophoretic mobility change in TSPP solution containing γ-CD and OTMA or HTMA, although the equilibrium constants for the ternary inclusion complexes could not be evaluated using the fluorescence method due to the small fluorescence intensity change.     

A comparison of three solvent-free techniques coupled with gas chromatography for determining trihalomethanes in urine samples

The analysis of volatile organic compounds in samples of biological fluids characterized by complex matrices is highly challenging. This paper presents a comparison of the results obtained in this field using three solvent-free techniques: thin-layer headspace with autogenous generation of liquid sorbent (TLHS) and membrane separation of the trace substances (pervaporation, PV), both of which are coupled to direct aqueous injection gas chromatography–electron capture detection (TLHS–DAI–GC–ECD and PV–DAI–GC–ECD), as well as conventional static headspace analysis followed by GC analysis with ECD detection (HS–GC–ECD). Basic validation parameters of the HS–GC–ECD, TLHS–DAI–GC–ECD and PV–DAI–GC–ECD procedures were calculated for water and urine samples. The calibration curves for all procedures were linear within the concentration range examined. The intermediate precisions of the procedures were good and reached about 10% (for all analytes) for HS–GC–ECD and TLHS–DAI–GC–ECD. The poorest results were obtained for PV–DAI–GC–ECD: about 20% for all analytes. The lowest method detection limits were obtained for the TLHS–DAI–GC–ECD procedure: below 0.0022 μg/L for all analytes. The enrichment factors did not differ significantly between water and urine samples, indicating little or no matrix effect in all procedures.     

Contamination assessment of heavy metal in surface sediments of the Wuding River, northern China

The heavy metal contents and the contamination levels of the surface sediments of the Wuding River, northern China, were investigated. Heavy metal concentration ranged in μg g⁻¹: 50.15–71.91 for Cr, 408.1–442.9 for Mn, 20.11–43.59 for Ni, 17.51–20.1 for Cu, 68.32–89.57 for Zn, 0.2–0.38 for Cd and 15.08–16.14 for Pb in the Wuding River sediments. The enrichment factor (EF) and the geo-accumulation index (Igeo) demonstrated that the sediments of the Wuding River had been polluted by Cd, Cr and Ni, which mainly originated from anthropogenic sources, whereas the sediments had not been polluted by Zn, Pb, Cu and Mn, which were derived from the crust. In addition, the assessment results of EF and Igeo suggested that the sediments of the Wuding River was “moderately” polluted by Cd and “unpolluted to moderately” polluted by Cr and Ni. The elevated urban sewage discharges and agriculture fertilizers usage in river basin are the anthropogenic sources of these heavy metals in river.     

Preparation, thermal, spectral and microscopic studies of calcium silicate hydrate–poly(acrylic acid) nanocomposite materials

A series of calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials were prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C–S–H from aqueous solution. The as-synthesized C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The XRD analysis of C–S–HPN materials suggest the intermediate organizations presenting intercalation of PAA within C–S–H and exfoliation of C–S–H. The SEM micrographs of C–S–H, PAA and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. The effect of the material’s composition on the thermal stability of a series of C–S–HPN materials along with PAA and C–S–H were studied by TG, DTA and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials.     

Modification and re-validation of the ethyl acetate-based multi-residue method for pesticides in produce

The ethyl acetate-based multi-residue method for determination of pesticide residues in produce has been modified for gas chromatographic (GC) analysis by implementation of dispersive solid-phase extraction (using primary–secondary amine and graphitized carbon black) and large-volume (20 μL) injection. The same extract, before clean-up and after a change of solvent, was also analyzed by liquid chromatography with tandem mass spectrometry (LC–MS–MS). All aspects related to sample preparation were re-assessed with regard to ease and speed of the analysis. The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades. The modifications were made with techniques currently commonly applied in routine laboratories, GC–MS and LC–MS–MS, in mind. The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person. Limits of quantification (LOQs) of 0.01 mg kg⁻¹ were achieved with both GC–MS (full-scan acquisition, 10 mg matrix equivalent injected) and LC–MS–MS (2 mg injected) for most of the pesticides. Validation data for 341 pesticides and degradation products are presented. A compilation of analytical quality-control data for pesticides routinely analyzed by GC–MS (135 compounds) and LC–MS–MS (136 compounds) in over 100 different matrices, obtained over a period of 15 months, are also presented and discussed. At the 0.05 mg kg⁻¹ level acceptable recoveries were obtained for 93% (GC–MS) and 92% (LC–MS–MS) of pesticide–matrix combinations.     

Quantification of human and veterinary antibiotics in water and sediment using SPE/LC/MS/MS

An analytical method was developed and tested for four different groups of veterinary antibiotics in both river water and sediment matrices. Solid phase extraction (SPE) was used to enrich and to clean up the aqueous sample. Also, Mcllvaine and ammonium hydroxide buffer solutions were used to extract the compounds from the sediment matrix. High performance liquid chromatography (HPLC) equipped with tandem mass spectrometry (MS/MS) was used to separate and quantify the samples. The range of recoveries (in percent) for tetracyclines (TCs), sulfonamides (SAs), macrolides (MLs), and ionophore polyethers (IPs) in the water matrix were 102.2–124.8, 76.6–124.3, 89.5–114.7, 82.7–117.5 with 1–13 (%) of relative standard deviation respectively with three different concentrations. For sediment, the percent recovery ranges were 32.8–114.8, 62.4–108.9, 53.4–128.4 and 51.3–105.4 for TCs, SAs, MLs and IPs, respectively. The relative standard deviation ranged from 16 – 27 (%) over three different concentrations. The limit of quantification (LOQ) was determined by two different methods and calculated to be in the range of 0.01–0.04 μg/l and 0.3–2.5 μg/kg for TCs, SAs, and MLs in water and sediment, respectively. For IPs, the LOQ was 0.001–0.003 μg/l in river water and 0.4–3.6 μg/kg for sediment. The sediment concentration measured in an agriculture-influenced river was much higher than in the overlying water matrix, indicating a high degree of sediment partitioning for these compounds.     

Composition and ethanol production potential of cotton gin residues

Cotton gin residue (CGR) collected from five cotton gins was fractionated and characterized for summative composition. The major fractions of the CGR varied widely between cotton gins and consisted of clean lint (5–12%), hulls (16–48%), seeds (6–24%), motes (16–24%), and leaves (14–30%). The summative composition varied within and between cotton gins and consisted of ash (7.9–14.6%), acid-insoluble material (18–26%), xylan (4–15%), and cellulose (20–38%). Overlimed steam-exploded cotton gin waste was readily fermented to ethanol by Escherichia coli KO11. Ethanol yields were feedstock and severity dependent and ranged from 58 to 92.5% of the theoretical yields. The highest ethanol yield was 191 L (50 gal)/t, and the lowest was 120 L (32 gal)/t.     

Investigation of the thermal properties of [Cd(hydet-en)2Pd(CN)4] AND [Zn(hydet-en)2Pd(CN)4] single crystals

Thermal properties of the single crystals have been investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. The thermodynamic parameters such as activation energy and enthalpy and thermal stability temperature of the samples were calculated from the differential thermal analysis (DTA) and TG data. The activation energies for first peak of DTA curves were found as 496.65 (for Cd–Pd) and 419.37 kJ mol^–1 (for Zn–Pd). For second peak, activation energies were calculated 116.56 (for Cd–Pd) and 173.96 kJ mol^–1 (for Zn–Pd). The thermal stability temperature values of the Cd–Pd and Zn–Pd compounds at 10°C min^–1 heating rate are determined as approximately 220.7 and 203°C, respectively. The TG results suggest that thermal stability of the Cd–Pd complex is higher than that of the Zn–Pd complex.     

Application of capillary isotachophoretic method to the determination of nitrate and nitrite ions in meat products

The application of capillary isotachophoretic method to the simultaneous determination of nitrates and nitrites in meat products was studied. Simple electrolyte system allowed separation of ions in standard solution with within-day and between-days coefficient of variation (CV) of relative step hight in the ranges 2.3–2.5% and 4.1–5.5%, respectively. The levels of nitrates and nitrites ranged from 3 to 65 mg/kg NaNO₃ and from 36 to 111 mg/kg NaNO₂. The coefficients of variation for nitrites were 0.7–3.5% and for nitrates 2.3–5.9%, that indicated satisfactory precision of the proposed method. The recoveries for meat samples spiked with nitrites and nitrates varied between 95–99% and 91–102%, respectively.     

Synthesis of Amido- and Diamidophosphites with Polyfluoroalkyl Substituents

Bis(polyfluoroalkyl) chlorophosphites and polyfluoroalkyl dichlorophosphites react easily with secondary amines (from –40 to –22°C, 1–3 h, CH2Cl2) in the presence or absence of triethylamine to form the corresponding bis(polyfluoroalkyl) diorganylamidophosphites or bis(diorganylamido) polyfluoroalkyl phosphites in the yield of up to 74%. Bis(polyfluoroalkyl) diorganylamidophosphites were also synthesized from diorganylamidodichlorophosphites and polyfluoroalkanols (–25 to –22°C, 2 h, Et3N–CH2Cl2) with a yield of 56–60%.     

Synthesis, thermal and structural characterization of nanocomposites for potential applications in construction

Several calcium silicate hydrate (C–S–H)-polymer nanocomposite (C–S–HPN) materials have been prepared by incorporating poly(acrylic acid) (PAA) into the inorganic layers of C–S–H during precipitation of quasicrystalline C-S-H from aqueous solution. The synthetic C–S–HPN materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS), thermogravimetry (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC). The XRD peaks of C–S–HPN materials suggest the intermediate organizations presenting both intercalation of PAA and exfoliation of C–S–H. The SEM images of C–S–H and C–S–HPN materials with different PAA contents exhibit the significant differences in their morphologies. Effects of the material compositions on the thermal stability of series of C–S–HPN materials along with PAA and C–S–H has been studied by TG, DTG and DSC. Three significant decomposition temperature ranges were observed on the TG curves of all C–S–HPN materials.     

Connection between the Ogilvie and the Murrell–Sorbie potential energy functions

Formulas for relating the parameters of the Murrell–Sorbie and the Ogilvie potentials are developed herein. Unlike the Simons–Parr–Finlan function, the Ogilvie potential is more easily connected with the Murrell–Sorbie potential, as evident from the longer range of agreement. The relationship is useful for generating high order Ogilvie potentials that exhibit the dissociation energy without experimentation, and for using the Murrell–Sorbie parameters in molecular softwares that adopt the Ogilvie function in their algorithms. The relations are invertible so that Ogilvie parameters from spectroscopic data can be applied in molecular softwares that employ Murrell–Sorbie potentials.