Optimization of the curing conditions of PVC plastisols based on the use of an epoxidized fatty acid ester plasticizer

The use of an epoxidized fatty acid ester (EFAE) as a natural-based plasticizer for plasticized PVC (P-PVC) has been evaluated in this work. The effect of the curing conditions has been studied by following several test techniques such as mechanical properties, thermal behavior, color changes, solvent migration and microstructure. Different curing processes at isothermal conditions (ranging from 160 °C to 220 °C) have been carried at curing times in the 6–16 min range. The optimum mechanical response (tensile strength values in the 9–10 MPa range and elongation at break close to 250%) is obtained for plastisols cured at 200 and 220 °C for 12 and 8 min curing times, respectively. These curing conditions also offer the lowest migration in n-hexane (lower than 11%) which is indicative of plasticizer total absorption. Furthermore, the use of these curing conditions does not lead to thermal degradation as confirmed by color measurements.     

5-(4-Carboxylphenylazo)-8-aminoquinoline as an analytical reagent for the spectrophotometric determination of gold

The synthesis and analytical application of 5-(4-carboxylphenylazo)-8-aminoquinoline (CPAQ) are described. A simple, rapid, selective, and sensitive spectrophotometric method for the determination of microgram amounts of gold is developed, based on the colour reaction between the metal ion and CPAQ in the presence of cetyltrimethyl ammonium bromide. Gold (III) reacts with the reagent in the ratio 1 3 (metal to ligand) in alkaline solution to form a blue-green complex with an absorption maximum at 608 nm. Beer's law is obeyed over the concentration range 0–1.8 g · ml^–1 (ppm) of gold. The molar absorptivity and Sandell's sensitivity of the method are 9.11 × 10⁴ l · mole^–1 · cm^–1 and 0.00216 g · cm^–2, respectively. The interference of various ions has been studied and conditions were developed for the determination of gold in an ore and anode slimes.     

Anaerobic biodegradation tests of poly(lactic acid) and polycaprolactone using new evaluation system for methane fermentation in anaerobic sludge

The anaerobic biodegradation tests of polycaprolactone (PCL) and poly(lactic acid) (PLA) powders were done at thermophilic temperature (55 °C) under aquatic conditions (total solid concentrations of the used sludge were 1.73% (undiluted sludge) and 0.86% (diluted sludge)) using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. The biodegradation of PCL powder (10 g, 125–250 μm) in the diluted sludge stopped in about 47 days when the biodegradability reached 92%. The biodegradability of PLA powder (10 g, 125–250 μm) in undiluted sludge was 91% at about 75 days. The biodegradability of PLA powder (10 g, 125–250 μm) in diluted sludge was 79% at about 100 days. The biodegradability of PLA powder (5 g, 125–250 μm) in diluted sludge was 80% at about 85 days. It was found that the PCL and PLA powders were quite degraded using the new evaluation method. In addition, the smaller particle size PCL powder was biodegraded faster.     

Development of a competitive liposome-based lateral flow assay for the rapid detection of the allergenic peanut protein Ara h1

A competitive lateral flow assay for detecting the major peanut allergen, Ara h1, has been developed. The detector reagents are Ara h1-tagged liposomes, and the capture reagents are anti-Ara h1 polyclonal antibodies. Two types of rabbit polyclonal antibodies were raised either against the entire Ara h1 molecules (anti-Ara h1 Ab) or against an immunodominant epitope on Ara h1 (anti-peptide Ab). All of them reacted specifically with Ara h1 in Western Blot against crude peanut proteins. Moreover, the anti-Ara h1 Ab was chosen for this assay development because of its highest immunoactivity to Ara h1-tagged liposomes in the lateral flow assay. The calculated limit of detection (LOD) of this assay is 0.45 g mL^–1 of Ara h1 with a dynamic range between 0.1 and 10 g mL^–1 of Ara h1 in buffer. Additionally, the visually determined detection range is from 1 to 10 g mL^–1 of Ara h1 in buffer. Results using this assay can be obtained within 30 min without the need of sophisticated equipment or techniques; therefore, this lateral flow assay has the potential to be a cost-effective, fast, simple, and sensitive method for on-site screening of peanut allergens.     

Comparative study of conventional and multivariate methods for aluminum determination in soft drinks by graphite furnace atomic absorption spectrometry

In the present study, conventional and multivariate methods were used to optimize conditions for direct determination of aluminum in soft drinks by electrothermal atomic absorption spectrometry. For the conventional method, the optimized experimental parameters were: pyrolysis and atomization temperatures and chemical modifier. A multivariate study was performed using factorial design and the optimized parameters were the same employed in the univariate method including pyrolysis time. For the conventional method, the optimal conditions obtained were: pyrolysis temperature of 1600 °C, atomization temperature of 2700 °C, and Zr as permanent modifier. For the factorial design in the multivariate optimization, the Pareto´s chart showed that the atomization temperature, the modifier, and the pyrolysis temperature presented a significant effect on the integrated absorbance and the interaction between pyrolysis temperature and pyrolysis time also had a significant effect on the signal. Better results were obtained using Zr as modifier. The surface response indicates that the lowest pyrolysis (1100 °C) and atomization temperatures (2350 °C) provide higher absorbance for aluminum in soft drinks. Characteristic mass of 23.4 and 19.4 pg and LOD of 17.9 and 11.3 μg L^− 1 was obtained to conventional and multivariate methods, respectively. The calibration was accomplished with standard addition in a range of 60–200 μg L^− 1 for conventional method and of 38–200 μg L^− 1for multivariate method with R higher than 0.99 for both conditions. Recoveries in both studies were nearly 100% with adequate precision for GFAAS analysis. For the Al concentrations level found in soft drinks, both experimental conditions are adequate as good results were obtained in recovery studies. The Al concentrations in different soft drinks range from 147.9 to 599.5 μg L⁻¹. Higher concentrations were found in soft drinks sold in Al cans than in PET bottles, indicating that contamination can occur.     

Polyol-mediated synthesis of Li4Ti5O12 nanoparticle and its electrochemical properties

Li₄Ti₅O₁₂ nanoparticles were precipitated from ethylene glycol solution of titanium tetra isopropoxide (Ti(O-iPr)₄) and Li₂O₂ by refluxing at 197 °C for 12 h. The obtained particles were filtered and dried at 100 °C for 12 h, and the dried powder samples were heated at 320, 500 and 800 °C for 3 h. The X-ray diffraction patterns of the obtained samples exhibited a good fit with the spinel phase. The field emission-SEM images of the dried powder sample and the samples heated at 320, 500 and 800 °C for 3 h showed a uniform spherical morphology with a particle size of 5, 8, 10 and 400 nm, respectively. According to the results of electrochemical testing, the dried powder sample and the samples heated at 320, 500, and 800 °C for 3 h showed initial capacities of 200, 310, 320, and 260 mA h/g, respectively, at a current density of 0.05 mA/cm². Nanosized (6–8 nm) particles with good crystallinity were obtained by controlling the synthesis conditions. The sample heated at 500 °C for 3 h exhibited a high capacity and an excellent rate capability over 60 cycles.     

Glass transition and state diagram for freeze-dried horse mackerel muscle

Glass transition temperatures of freeze-dried horse mackerel muscle conditioned at various water activities at 25 °C were determined by differential scanning calorimetry (DSC). High moisture content (>0.33 g/g, d.b.) samples obtained by adding liquid water into freeze-dried samples, were also analyzed. The state diagram was composed of the freezing curve and the glass transition line, which were fitted according to Clausius–Clapeyron model and Gordon–Taylor model, respectively. The state diagram yielded maximally freeze-concentrated solutes at 0.786 solids with the characteristic temperature of glass formation being −83.1 °C. The state diagram of horse mackerel muscle developed in this work could be used to predict the stability during frozen storage and in dried conditions as well as in designing drying and freezing processes.     

Feasibility of employing permanent chemical modifiers for the determination of cadmium in coal using slurry sampling electrothermal atomic absorption spectrometry

Iridium and ruthenium, alone and in combination with tungsten, thermally deposited on the platform of a transversely heated graphite tube, were investigated for their suitability as permanent chemical modifiers for the determination of cadmium in coal slurries by electrothermal atomic absorption spectrometry (ET AAS). The conventional mixed palladium and magnesium nitrates (Pd–Mg) modifiers, added in solution, were also investigated for comparison. The latter one showed the best performance for aqueous solutions, and the mixed W–Ir and W–Ru permanent modifiers had the lowest stabilizing power. All of the investigated modifiers lost some of their stabilizing power when coal slurries were investigated. The Pd–Mg modifier, pure Ir and Ru, and a mixture of 300 μg W + 200 μg Ir could stabilize Cd at least to a pyrolysis temperature of 600 °C, whereas all the other combinations already failed at temperatures above 500–550 °C. Additional investigations of the supernatant liquid of the slurries supported the assumption that the high acid concentration of the slurries and/or a concomitant leaching out of the coal might be responsible for the reduced stabilizing power of the modifiers. The maximum applicable pyrolysis temperature of 600 °C was not sufficient to reduce the background absorption to a manageable level in the majority of the coal samples. High-resolution continuum source ET AAS revealed that the continuous background absorption was exceeding values of A = 2, and was overlapping with the analyte signal. Although the latter technique could correct for this background absorption, some analyte was apparently lost with the rapidly vaporizing matrix so that the method could not be considered to be rugged. A characteristic mass of 1.0 pg and a detection limit of 0.6 ng g^− 1 could be obtained under these conditions.     

Preparation and characteristics of NiO-coated nano-fibriform silica

NiO-coated nano-fibriform silica (NFS) was prepared by an excessive soakage method and was characterized using transmission electron microscopy, X-ray diffraction, and physical N₂ adsorption techniques under different conditions. The results demonstrate that the coated NiO is of a cubic crystal form. The best preparation conditions are incubation in a water bath at 95 °C for 2 h and drying at 45 °C for 17 h, which lead to a higher NFS utilization ratio and thus lower cost, and a well-distributed NiO coating on the carrier NFS. Nitrogen adsorption isotherms for NiO-coated NFS are similar to a type IV curve, with a specific surface area of 292.7 m²/g, adsorptive capacity of 379.2 cm³/g, and pore volume of 0.59 cm³/g. The average pore diameter of NiO-coated NFS is 8.01 nm, but most pore diameters are in the range 2.1–3.9 nm. Comparison of NiO-coated NFS and NiO(Ni)-coated sol–gel silica as catalysts reveals that NiO-coated NFS may be an effective catalyst and that NFS may be a good catalyst carrier.     

Chemical reaction in chromatographic columns : Dehydrogenation of ethane over cadmium-exchanged zeolite 4A

Pulsed-flow techniques were used to detect considerable differences in the heats of adsorption of ethane and ethylene on various cadmium-exchanged zeolites 4A at temperatures up to 500°C. Higher values (about 10.0 kcal/mole) were observed for ethylene than for ethane (5.0 kcal/mole) at 300–400°C. Experimental verification is provided pertaining to the dehydrogenation of ethane in a gas chromatographic reactor. By appropriate choice of the reaction conditions, conversions up to 80% per pass could easily be obtained at temperatures (400–500°C) at which the thermodynamic equilibrium for a diluted ethane stream (Pc⁺₂ = 0.01-0.1 P_tot.) would not permit more than 25%.     

Spectrophotometric determination of gold by reaction with molybdate and nile blue in the presence of PVA

A spectrophotometric method for the determination of gold has been developed, based on the reaction of gold(III) with molybdate and nile blue (NB) to form an ion-association complex in the presence of poly(vinyl alcohol). The molar absorptivity at 595 nm is 2.71 × 10⁵ l mol^–1 cm^–1. Beer's law is obeyed over the range 0–16 g of gold per 25 ml. The relative standard deviation evaluated from seven independent determinations of 0.4 g/ml of gold is 2.6%. The limit of detection is 0.011 g/ml. The molar ratio of Au to NB in the complex is established to be 1 2. Over 30 foreign ions were tested for interference; Pt(IV), Sb(III), W(VI) and SiO ₃ ^2– interfered and had to be separated from gold on polyurethane foam. The method can be applied to the spectrophotometric determination of trace amounts of gold in powdered carbon and some ores.     

The mutual catalytic effect in kinetic reactions and its application to simultaneous determination of binary components

The mutual catalytic effect between iron(II) and antimony(III) on the chromium(VI)-iodide kinetic reactions has been studied by stopped-flow FIA. The concept of mutual catalytic coefficient is defined. The deviations from additive principles of absorbance within certain concentration ranges in previous procedures can be compensated effectively, by introducing the mutual catalytic coefficient into the simultaneous determination of a binary mixture with stopped-flow-FIA method. The linear concentration ranges have been enlarged, 0–3.5 g/ml Fe(II) and 0–3.7 g/ml Sb(III) compared with 0–1.2 g/ml Fe(II) and 0–2.0 g/ml Sb(III) without use of the coefficient. Iron and antimony contents in wastewater, a simulated sample and a zinc standard were determined, the recoveries and relative standard deviations being, respectively, 99.8–101.3% and 2.7–3.6% for iron and 95.4–100.3% and 2.3–5.3% for antimony compared with 95.2–98% and 3.0–4% for iron and 96–104% and 4.5–4.8% for antimony, assuming additivity.     

Improvement in performance of a direct ethanol fuel cell: Effect of sulfuric acid and Ni-mesh

A direct ethanol fuel cell (DEFC) is developed with low catalyst loading at anode and cathode compared to that reported in the literature. Pt/Ru (40%:20% by wt.)/C and Pt-black were used as anode and cathode catalyst with loadings in the range of 0.5–1.2 mg/cm². The temperatures of anode and cathode were varied from 34 °C to 110 °C, and the pressure was maintained at 1 bar. Although low catalyst loading was used, the cell performance is enhanced by 40–50% with the use of low concentration of sulfuric acid in ethanol and Ni-mesh as current collector at the anode. The power density 15 mW/cm² at 32 mA/cm² of current density is obtained from the single cell with 0.5 mg/cm² loading of Pt–Ru/C at anode (90 °C) and Pt-black at cathode (110 °C). The performance of DEFC increases with the increase in ethanol and sulfuric acid concentrations, electrocatalyst loadings up to 1 mg cm⁻² at anode and cathode. However, the performance of DEFC decreases with further increase in electrocatalyst loading.     

A pyrolysis-GC–MS investigation of poly(vinyl phenyl ketone)

The thermal decomposition process and pyrolysis products of poly(vinyl phenyl ketone) (PVPK) were investigated by thermogravimetric analysis (TGA) and on-line pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS). TGA showed a largest weight loss rate around 380 °C. Py-GC–MS was used for the qualitative analysis of the pyrolysis products at 350, 500, 600, 700 and 850 °C. The major volatile thermal decomposition product was found to be 1-phenyl-2-propenone, which dominated all other volatile species especially under the least severe pyrolysis conditions (<600 °C). At higher temperatures a much wider range of pyrolysis products was obtained. The results have been interpreted assuming that primary random chain scission reactions occur followed by typical unzipping mainly producing monomer units; detachment of the side-group occurs only under more severe pyrolysis conditions. Py-GC–MS showed to be effective in PVPK detection in ink and paint formulations.     

The role of medium radiation dose on microbiological safety and shelf-life of some traditional soups

Irradiation at medium doses in combination with cryogenic condition along the process to ensure the safety, quality and to extend the shelf-life of prepared meals have been investigated. Semi-concentrated black, ox-tail, chicken vegetable and chicken sweet corn soups were individually packed in a dry laminate pouch of PET 12 μ/LDPE adh.2 μ/Al–foil 7 μ/LDPE adh/LLDPE (C₄) 50 μ under vacuum followed by freezing for 24 h at −18 °C prior to irradiation with doses of 1, 3, 5 and 7 kGy at cryogenic condition (−79 °C), respectively. Both the non-irradiated and irradiated prepared meals were then stored in refrigerator at 5±2 °C. Non-irradiated and the irradiated samples at 1 kGy were mostly damaged after a week of storage. Gamma irradiation at doses of 5–7 kGy for the soups could reduce microbial load by about 2–3 log cycles, respectively, without affecting the physical–chemical parameters and palatability within 2–3 months while the unirradiated samples could only withstand for 1 month storage time.     

Polyelectrolyte-mediated non-micellar synthesis of monodispersed ‘aggregates’ of gold nanoparticles using a microwave approach

‘Aggregates’ of monodispersed gold nanoparticles were synthesized for the first time in large quantities. Those particles were made in presence or in absence of gold seed in a polyelectrolyte solution using microwave heating for about 30–60 s. The average diameters of the particles calculated from TEM and SEM analysis were 22 ± 2 nm. Our analysis found that the polyelectrolyte acted as a reducing as well as a stabilizing agent. It controlled the growth of particles by aligning them on the polymeric chain and the nanoparticles were subsequently self-assembled to form an ‘aggregate’ structure. The synthetic procedure is very fast and the particles are stable for at least 6 months under ambient conditions.     

Determination of Ionol by Voltammetry and Coulometric Titration

Procedures were developed for determining ionol by voltammetry and by coulometric titration with electrogenerated chlorine using the amperometric indication of the titration end point. Possible mechanisms of ionol oxidation with electrogenerated chlorine and its electrochemical oxidation at a glassy carbon and a gold electrode were discussed. Procedures were developed for determining ionol in mineral oil in analytical ranges from 1.0 × 10^–4 to 1.0 × 10^–2 M (RSD = 9%) and from 3.0 × 10^–5 to 4.0 × 10^–3 M (RSD = 9%) using a glassy carbon and a gold electrode, respectively. The detection limits for ionol at the glassy carbon and gold electrode were 2.8 × 10^–4 and 1.0 × 10^–5 M, respectively. The detection limit in coulometric titration was 20 g/mL.     

Spectrophotometric microdetermination of amoxicillin and neomycin with chloranil

Ampicillin trihydrate (12.5–750 μg) is determined spectrophotometrically using chloranil as π-acceptor at pH 9. The method is relatively accurate (with a recovery of 100 ± 1.0%) and precise (RSD 1.7%) and can be used successfully for capsules and ampoules.     

Rheological properties of reversible thermo-setting in situ gelling solutions with the methylcellulose–polyethylene glycol–citric acid ternary system (2): Effects of various water-soluble polymers and salts on the gelling temperature

The influences of various salts and water-soluble polymers on the phase transition temperature of thermo-setting gels prepared by combining methylcellulose (MC)–sodium citrate (SC)–polyethylene glycol (PEG) at appropriate ratios (the MC–SC–PEG system) were investigated. Concerning cations, comparison of the phase transition temperature between SC and tripotassium citrate (PC) showed a rapid increase in the viscosity of SC between 20 °C and 25 °C and an increase in the viscosity of PC between 30 °C and 35 °C. Concerning the valency of anions, comparisons among SC, disodium tartrate dihydrate (ST), disodium maleate hemihydrates (SM), and sodium sulfate (SS) showed a rapid increase in the viscosity of trivalent SC between 20 °C and 25 °C and changes in the viscosity of the three bivalent sodium salts (ST, SM, and SS) at ≥30 °C. Thus the phase transition temperature decreased with an increase in the valency of anions.Subsequently, the influences of various water-soluble polymers on the gelling temperature were compared. Using polyvinylpyrrolidone (PVP) instead of PEG, the gelling temperature decreased with an increase in the PVP concentration even without the addition of SC. Unlike PVP, the addition of xanthan gum as a viscosity-increasing polysaccharide did not reduce the gelling temperature irrespective of its concentration.Temperature-associated changes in viscosity were observed at a fixed SC concentration with changes in the concentration of PVP or PEG. The gel phase transition temperature increased from 46 °C to 50 °C in gels not containing PVP or PEG. The viscosity did not differ between the addition of PVP or PEG at a low concentration and its absence. However, the viscosity clearly changed after the addition of each agent at a high concentration.     

Amperometric PMMA-microchip with integrated gold working electrode for enzyme assays

The use of a gold film in-channel detector combined with a poly(methyl methacrylate) (PMMA) CE microchip has been tested for alkaline phosphatase (AP) enzymatic assays. Tris-borate or Tris-Gly (pH 9.0, 50 mmol L^–1) buffer solutions were appropriate as running buffer. Signals for three common AP products: -naphthol, p-nitrophenol, and ascorbic acid, were obtained. They were reproducible (RSD 4.4% for six successive electropherograms corresponding to 5 mmol L^–1 -naphthol solution) and the response was dependent on concentration (linear relationship for ascorbic acid solutions between 5 and 20 mmol L^–1 concentration). Use of an end-channel gold film electrode was also investigated. If one of the reagents (substrate or enzyme) is included in the running buffer, two different types of enzymatic assay are feasible in less than 3 min.