Voltammetric Behavior of Testosterone on Bismuth Film Electrode: Highly Sensitive Determination in Pharmaceuticals and Human Urine by Square‐Wave Adsorptive Stripping Voltammetry

In this paper, an electrochemical application of bismuth‐film electrode (BiFE) fabricated via ex‐situ electrodeposition onto a glassy carbon electrode for testosterone determination was investigated in aqueous and aqueous/surfactant solutions. In cyclic voltammetry, the compound showed one irreversible and adsorption‐controlled reduction peak. The BiFE revealed good linear response in the examined concentration range of 1 to 45 nmol L^?1 testosterone in Britton? Robinson buffer, pH 5.0 containing 3 mmol L^?1 cetyltrimethylammonium bromide. The limit of detection was 0.3 nmol L^?1 (0.09 ng mL^?1). Finally, the BiFE was satisfactorily applied for quantitation of testosterone in both pharmaceutical (oil‐based ampoule) and biological (human urine) samples.     

Fabrication of a Novel Polymeric Scaffold for Amperometric Laccase Biosensor

Present work displays the preparation of an electrochemical biosensor using a conjugated polymer and laccase enzyme for catechol quantification in samples. The biosensing system is based on an enzyme immobilization on polymer modified graphite transducer surface. For that purpose, a random conjugated polymer, thienothiophene‐benzoxadiazole‐alt‐benzodithiophene (BOTT), was coated onto a graphite electrode surface via drop casting method followed by immobilization of a biomolecule (laccase) for sensing experiments. Herein, for the first time, we proposed a BOTT polymer as an inexpensive and effective way to fabricate highly sensitive and fast response biosensors. The proposed sensing system possessed superior properties with 0.38 μM limit of detection and 110.81 μA mM^?1 sensitivity. Furthermore, cyclic voltammetry and scanning electron microscopy techniques were used to examine the surface modifications. The proposed system could be useful for many future studies for catechol quantification in environmental samples.© 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2333–2339     

Investigation of Copolymers of Thiophene‐Functionalized Polystyrene with Pyrrole by Pyrolysis Mass Spectrometry

The thermal and structural characterization of electrochemically synthesized thiophene‐functionalized polystyrene and pyrrole (PS/PPy) and their copolymers were investigated by direct pyrolysis mass spectrometry. The pyrolysis data confirmed the growth of polypyrrole onto the pendant thiophene moiety of polystyrene. It is determined that the electrolytic film has different properties from the mechanical mixture and the related homopolymers.     

A pyrolysis mass spectrometry study of polythiophene copolymers

The thermal behaviour of copolymers of thiophene with decanedioic acid bis-(2-thiophen-3-yl-ethyl)ester (DATE) and terephthalic acid bis-(2-thiophen-3-yl-ethyl)ester (TATE) prepared by potentiostatic polymerization was studied via pyrolysis mass spectrometry. It was determined that the electrolytic films correspond to the related homopolymers. The increase in thermal stability of ester linkages, and evolution of characteristic degradation products of TATE and DATE together with thiophene based products above 400 °C confirmed copolymer formation.     

Invariance and efficiency of convex representations

We consider two notions for the representations of convex cones G-representation and lifted-G-representation. The former represents a convex cone as a slice of another; the latter allows in addition, the usage of auxiliary variables in the representation. We first study the basic properties of these representations. We show that some basic properties of convex cones are invariant under one notion of representation but not the other. In particular, we prove that lifted-G-representation is closed under duality when the representing cone is self-dual. We also prove that strict complementarity of a convex optimization problem in conic form is preserved under G-representations. Then we move to study efficiency measures for representations. We evaluate the representations of homogeneous convex cones based on the “smoothness” of the transformations mapping the central path of the representation to the central path of the represented optimization problem. Research of the first author was supported in part by a grant from the Faculty of Mathematics, University of Waterloo and by a Discovery Grant from NSERC. Research of the second author was supported in part by a Discovery Grant from NSERC and a PREA from Ontario, Canada.     

Synthesis and characterization of nanomagnetite thermosets based on benzoxazines

Nanomagnetite thermosets were obtained by thermally activated ring opening copolymerization of benzoxazine groups coated on the surface of the nanomagnetite with bare benzoxazine. For this purpose, carboxylic acid containing 1,3‐benzoxazine was synthesized and covalently bonded on magnetite nanoparticles by postcoating method. The average size of benzoxazine coated nanoparticles was 40–100 nm as determined by Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) measurements. The crystal structure of benzoxazine coated nanoparticles was shown to be magnetite by X‐ray diffraction (XRD) analysis. Thermally activated curing behavior of nanomagnetite‐benzoxazines has also been studied by differential scanning calorimetry (DSC). Magnetic and thermal properties of the cured samples were investigated. It was shown that the precursor nanomagnetite benzoxazine and cured samples exhibited typical ferromagnetic character with low coercivities between 1.5 and 2.5 Oe. The cured samples showed high thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6780–6788, 2008     

Superluminal propagation and information transfer: A statistical approach in the microwave domain

Signal velocity is calculated in a medium with negative group delay (NGD). By accounting for the medium and the detector noise sources, the time varying probability of error at the detector [Pe(t)$\mathit{Pe}(t)$] is evaluated in the NGD channel and a normal dispersion channel. The scheme in which Pe(t)$\mathit{Pe}(t)$ falls below a threshold at earlier time, implies faster information transfer. It is found that the signal velocity depends on the detector type and the relative noise strength of the detector with respect to the channel. Finally, it is shown that NGD channels can be useful in applications that are limited by the detector noise.     

Polymerization of Bis(Pyridine)bis-(2,4,6-tribromophenoxo)copper(II) Complex (Py2Cu(TBrP)2) by Electrooxidation and Structural Characterization by 1H-NMR, 13C-NMR,and FTIR Spectroscopies

Abstract

Electroinitiated polymerization of bis(2,4,6-tribromophenoxo)- bis(pyridine)copper(II) complex was achieved in dimethylformamide-tetrabutylammonium tetrafluoroborate solvent-electrolyte couple under air or nitrogen at room temperature by constant potential electrolysis. Polymerization conditions were based on the peak potentials measured by cyclic voltammetry. The structural analyses of the polymers were done by ¹H-NMR, ¹³C-NMR, and FTIR spectral analyses along with molecular weight measurements by cryoscopy. The poly(dibromo phenylene oxide)s obtained only at oxidation potentials in either atmosphere were found to be highly linear, indicating mainly 1,4-catenation was taking place.     

Preparation and application of a polythiophene solid‐phase microextraction fiber for the determination of endocrine‐disruptor pesticides in well waters

A robust solid‐phase microextraction fiber was fabricated by electropolymerization of thiophene on a stainless steel wire. This fiber was applied for the determination of endocrine‐disruptor pesticides, namely, chlorpyrifos, penconazole, procymidone, bromopropylate, and λ‐cyhalothrin in well waters by a headspace solid‐phase microextraction procedure. Operational parameters, namely, pH, sample volume, adsorption temperature and time, desorption temperature, stirring rate, and salt amount were optimized as 7.0, 8 mL, 70°C and 20 min, 250°C, 600 rpm, and 0.3 g/mL, respectively. The separation power of GC was coupled with the excellent sensitivity of the developed fiber enabling us to determine pesticide mixtures simultaneously in a ng/mL range. The LOD was in the range of 0.02–0.64 ng/mL. The method was successfully applied for the selective and sensitive determination of target pesticides in well water samples with acceptable recovery values (92–110%). The polythiophene fiber gives satisfactory results compared with commercial fibers. Commonly used pesticides with different polarities were chosen as representative compounds to search the applicability of the fiber for well water analysis collected from vineyards.