Fabrication of Nano Flower‐shaped Platinum on Glassy Carbon Electrode as a Sensitive Sensor for Lead Electrochemical Analysis

Platinum nanoflowers modified glassy carbon electrodes (PtNFs/GCE) was fabricated simply for lead determination in water samples. The modified electrodes were prepared by electrodeposition in hexachloroplatinic acid solution at constant potential. The influence of deposition time and potential on surface morphology, chemical composition, electrochemical properties of electrode were investigated. At ?0.2 V of potential and 150 s of deposition duration, platinum developed as nanoflower shape and scattered densely all over the glassy carbon surface, producing the largest electrochemically active surface areas. The highest differential pulse stripping voltammetry (DPSV) signal of lead was obtained by using the prepared electrode. Under optimized experimental condition of electrolyte, accumulation potential and time, the peak current was found to be linear proportion to lead concentration in range of 1 to 100 μg L^?1 (slope=0.371) with a limit of detection of 0.398 μg L^?1. The method has good repeatability and reproducibility with relative standard deviations of 1.47 % and 4.83 %, respectively. The modified PtNFs/GCE also demonstrated an excellent long‐term stability with only 9 % decrease in Pb peak current over 30 days. Moreover, the performance of the modified PtNFs/GCE in determination of Pb(II) in two industrial wastewaters was good agreement with data obtained by a graphite furnace atomic absorption spectrometry (GFAAS) method.     

Separation of histamine and its metabolites using glass capillary gas chromatography and a nitrogen detector

Complete separation of the TMS derivatives of histamine, 1-methyl histamine and 3-methyl histamine was achieved in two minutes in a 7 m × 0.25 mm column coated with SP 2250. Using NPD, histamine was detectable at levels as low as 20 pg. This offers a rapid, sensitive procedure with potential for clinical diagnosis and food analysis.     

Residual determination and risk assessment of buprofezin in plum (Prunus domestica) grown in open‐field conditions following the application of three different formulations

This study was conducted to characterize the residual level and perform a risk assessment on buprofezin formulated as an emulsifiable concentrate, wettable powder, and suspension concentrate over various treatment schedules in plum (Prunus domestica). The samples were extracted with an AOAC quick, easy, cheap, effective, rugged, and safe, ‘QuEChERS’, method after major modifications. As intrinsic interferences were observed in blank plum samples following dispersive‐solid phase extraction (consisting of primary secondary amine and C₁₈ sorbents), amino cartridges were used for solid‐phase extraction. Analysis was carried out using liquid chromatography with diode array detection and confirmed by liquid chromatography–tandem mass spectrometry. The method showed excellent linearity with determination coefficient (R² = 1) and satisfactory recoveries (at two spiking levels, 0.5 and 2.5 mg/kg) between 90.98 and 94.74% with relative standard deviation (RSD) ≤8%. The limit of quantification (0.05 mg/kg) was considerably lower than the maximum residue limit (2 mg/kg) set by the Codex Alimentarius. Absolute residue levels for emulsifiable concentrates were highest, perhaps owing to the dilution rate and adjuvant. Notably, all formulation residues were lower than the maximum residue limit, and safety data proved that the fruits are safe for consumers. Copyright © 2016 John Wiley & Sons, Ltd.     

Image Restoration and Decomposition via Bounded Total Variation and Negative Hilbert-Sobolev Spaces

We propose a new class of models for image restoration and decomposition by functional minimization. Following ideas of Y. Meyer in a total variation minimization framework of L. Rudin, S. Osher, and E. Fatemi, our model decomposes a given (degraded or textured) image u ₀ into a sum u+v. Here u∈BV is a function of bounded variation (a cartoon component), while the noisy (or textured) component v is modeled by tempered distributions belonging to the negative Hilbert-Sobolev space H ^−s . The proposed models can be seen as generalizations of a model proposed by S. Osher, A. Solé, L. Vese and have been also motivated by D. Mumford and B. Gidas. We present existence, uniqueness and two characterizations of minimizers using duality and the notion of convex functions of measures with linear growth, following I. Ekeland and R. Temam, F. Demengel and R. Temam. We also give a numerical algorithm for solving the minimization problem, and we present numerical results of denoising, deblurring, and decompositions of both synthetic and real images.     

Simultaneous analysis of all five organic priority pollutant fractions

Acrolein, acrylonitrile, volatile organics, base/neutral extractables, acid extractables, and pesticide fraction organics are analyzed in a single chromatographic run. This is accomplished by injecting the extractable organics, then applying a cryogenic focus to the front of the column, and desorbing the volatile components. The column utilized for this procedure is a fused silica open tubular (FSOT) column coated with the liquid phase SE-54. Minimum detection limits of this procedure by electron impact GC/MS are shown to be? 1 μg/liter in tests conducted on actual water samples.     

Thermal/mechanical damage of 6061-T6 aluminum tensile specimen

As a 6061-T6 aluminum coupon specimen is stretched, energy is being converted from mechanical work to heat. This irreversible process of material damage is detected experimentally by measuring the change in surface temperature. Contrary to the ordinary notion that the material would heat up when loaded, it actually cools before returning to the ambient condition. The recovery time was approximately 26 sec for a displacement rate of 8.467·10⁻⁵ m/sec and 200 sec when the displacement rate is reduced by one of magnitude. Cooling and heating is a rate dependent process. Three sets of temperature data were obtained for each of the displacement rates and they coincide with those prediced from the energy density theory that accounts for the nonhomogeneous dissipation of energy at every location in the specimen.Unlike any classical theories in mechanics, the energy density theory determines the stress and strain response of each element in the specimen only from a knowledge of the initial material stiffness and the displacement time rate. This is necessary because the local strain rates for elements near the center and edge of the specimen can differ by a wide margin. The so-called uniaxial stress and strain curve is then obtained by taking the average of all the elements. The results agreed extremely well with those measured experimentally for the 6061-T6 aluminum. Obtained analytically are also the thermal conductivity coefficients that are loading rate dependent and anisotropic in character due to stretching in the longitudinal direction. Their values tend to stabilize beyond the cooling/heating period.     

Differential reflectance spectrophotometry-I High-reflectance method for determination of micro amounts of substances resolved on thin plates

The basic principles of differential high-reflectance spectroscopy are discussed from the standpoint of the determination of substances resolved on chromatoplates. Results obtained with the use of two systems, nickel dimethylglyoximate or copper neocuproinate adsorbed on cellulose, are used as illustrations. A graphical method for selecting the optimum concentration range for analysis and for determining the maximum accuracy attainable is also outlined. When contrasted with the conventional method of measuring reflectance, the technique promises substantially increased accuracy over a wider concentration range and seems particularly suited to the analysis of trace amounts of material.     

Simultaneous detection of fluquinconazole and flusilazole in lettuce using gas chromatography with a nitrogen phosphorus detector: decline patterns at two different locations

Method validations in addition to decline patterns of fluquinconazole and flusilazole in lettuce grown under greenhouse conditions at two different locations were investigated. Following the application of fluquinconazole and flusilazole at a dose rate of 20 mL/20 L water, lettuce samples were collected randomly for up to 7 days post‐application, and simultaneously extracted with acetone, purified through solid‐phase extraction, analyzed via gas chromatography with a nitrogen phosphorus detector, and confirmed through gas chromatography–mass spectrometry. The linearity was excellent, with determination coefficients (R²) between 0.9999 and 1.0. The method was validated in triplicate at two different spiking levels (0.2 and 1.0 mg/kg) with satisfactory recoveries between 75.7 and 97.9% and relative standard deviations of <9. The limit of quantification was 0.01 mg/kg. Both analytes declined very quickly, as can be seen from the short half‐life time of <4 days. Statistical analysis revealed significant differences between residues at different days of sampling, except at 7 days post‐application (triple application). At that point, the decline patterns of fluquinconazole and flusilazole were independent of application rate, location, temperature and humidity. Copyright © 2015 John Wiley & Sons, Ltd.