Potentiometric Membrane Sensor for Determination of Saccharin

A potentiometric poly(vinyl chloride) membrane sensor for determination of saccharin is described. It is based on the use of Aliquat 336S-saccharinateion-pair as an electroactive material in plasticized PVC membranes with o-nitrophenyloctylether or dioctylphthalate. The sensor is conditioned for at least two days in 0.1 mol L⁻¹ sodium saccharinate before use. It exhibits fast, stable and Nernstian response for saccharinate ions over the concentration range of 1.0 × 10⁻¹–5.0 × 10⁻⁵ mol L⁻¹ and pH range of 4.5–11. The sensor is used for determination of saccharin in some dosage forms. Results with an average recovery of 101% and a mean standard deviation of 0.2% are obtained which is compared favourably with data obtained using the British pharmacopoeia method. The sensor shows reasonable selectivity towards saccharin in presence of many anions and natural sweeteners.     

New Layered Double Hydroxide, Zn–Ti LDH : Preparation and Intercalation Reactions

The layered double hydroxide (LDH) well known for its abilityto intercalate anionic compounds has been prepared conventionallyonly with bivalent and trivalent cations. In this study, Zn–Ti LDH consisting of bivalent and tetravalent cations was prepared, andreacted with organic monocarboxylic, dicarboxylic and aromatic acidsat high or room temperature. XRD patterns of the prepared LDH(Zn–Ti-CO₃) showed that interlayer spacing of the LDH was 0.67 nm. The value was small compared to the usual LDH (Zn–Al–CO₃)of 0.76 nm in the case of carbonate anion as the guest. Also, DTA,TG and DTG analysis indicated that the electrostatic force betweenthe layers and carbonate anions increased where the carbonate anionsin Zn–Ti LDH decomposed at 255 °C while those inZn–Al–CO₃ decomposed at 230–240 °C.     

Thermal properties stability of UV irradiated PVA nanohybrid composites

Zn‐Al‐salicylic nanohybrid layers have been prepared and used as fillers for polyvinyl alcohol (PVA). Nanohybrid layers of a broad absorption area in UV region were completely and uniformly dispersed in a continuous polymer matrix. PVA and PVA nanohybrid composite (NHC) films were exposed to UV irradiation. Thermal properties (diffusivity, effusivity, and conductivity) of both have been measured through photoacoustic technique before and after UV irradiation. Thermal parameters of PVA suffered from a quick deterioration with UV exposure due to reduction of the phonon mean free path as a result of molecular chain scissions. However, significant stability in such parameters of NHC has been obtained under the influence of UV irradiation. This thermal properties stability may be an important step on the way of obtaining photostable polymer NHC. Copyright © 2012 John Wiley & Sons, Ltd.     

Polyvinylimidazole/sol–gel composite as a novel solid‐phase microextraction coating for the determination of halogenated benzenes from aqueous solutions

A polyvinylimidazole/sol–gel composite is proposed as a novel solid‐phase microextraction fiber to extract five halobenzenes from the headspace of aqueous solutions in combination with gas chromatography with mass spectrometry. The prepared fiber was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The obtained results showed that porous polyvinylimidazole/sol–gel composite was chemically deposited on fused silica fiber. The effect of important extraction parameters including extraction temperature, extraction time, and salt content were investigated. The optimum conditions were as follows: extraction temperature 25°C, extraction time 20 min, and salt concentration 30 w/v%. Detection limits and relative standard deviations of the developed method for halogenated benzenes were below 0.1 pg/mL and 15%, respectively. Repeatability of the proposed method, explained by relative standard deviation, varied between 5.48 and 9.15% (n = 5). The limits of detection (S/N = 3) ranged between 0.01 and 0.10 ng/L using gas chromatography with mass spectrometry with selected ion monitoring mode. For real sample analysis, three types of water samples with different matrices (ground, surface, and tap water) were studied. The optimized procedure was applied to extraction and method validation of halogenated benzenes in spiked water samples.     

Analysis of tamoxifen and its main metabolites in plasma samples of breast cancer survivor female athletes: Multivariate and chemometric optimization

A sensitive method based on liquid chromatography combined with a diode array detector was developed and validated to simultaneously determine tamoxifen, and its active metabolites N-desmethyltamoxifen, 4-hydroxytamoxifen, and endoxifen in human plasma samples. The green and sustainable vortex-assisted dispersive liquid-phase microextraction technique based on the natural hydrophobic deep eutectic solvent was used for the extraction and preconcentration of the analytes. Chemometrics and multivariate analysis were used to optimize the independent variables including the type and volume of deep eutectic solvent, extraction time, and ionic strength. Under optimal conditions, calibration curves were linear in a suitable range with the lower limits of quantification (0.8–10.0 μg/L), which covered the relevant concentrations of the analytes in plasma samples for a clinical study. Intra- and interday precision evaluated at three concentrations for the analytes were lower than 8.2 and 12.1%, respectively. Accuracy was in the range of 94.9–104.7%. The applicability of the developed method on human plasma samples illustrated the range 45.1–72.8, 98.4–128.3, 0.9–1.2, and 2.7–6.1 μg/L for tamoxifen, N-desmethyltamoxifen, 4-hydroxytamoxifen, and endoxifen, respectively. The validated method can be effective for the pharmacokinetics, pharmacodynamics, and therapeutic drug monitoring studies of tamoxifen and its main metabolites in biological fluids.     

Enhancement of β-Glucan Biological Activity Using a Modified Acid-Base Extraction Method from Saccharomyces cerevisiae

Beta glucan (β-glucan) has promising bioactive properties. Consequently, the use of β-glucan as a food additive is favored with the dual-purpose potential of increasing the fiber content of food products and enhancing their health properties. Our aim was to evaluate the biological activity of β-glucan (antimicrobial, antitoxic, immunostimulatory, and anticancer) extracted from Saccharomyces cerevisiae using a modified acid-base extraction method. The results demonstrated that a modified acid-base extraction method gives a higher biological efficacy of β-glucan than in the water extraction method. Using 0.5 mg dry weight of acid-base extracted β-glucan (AB extracted) not only succeeded in removing 100% of aflatoxins, but also had a promising antimicrobial activity against multidrug-resistant bacteria, fungi, and yeast, with minimum inhibitory concentrations (MIC) of 0.39 and 0.19 mg/mL in the case of resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa, respectively. In addition, AB extract exhibited a positive immunomodulatory effect, mediated through the high induction of TNFα, IL-6, IFN-γ, and IL-2. Moreover, AB extract showed a greater anticancer effect against A549, MDA-MB-232, and HepG-2 cells compared to WI-38 cells, at high concentrations. By studying the cell death mechanism using flow-cytometry, AB extract was shown to induce apoptotic cell death at higher concentrations, as in the case of MDA-MB-231 and HePG-2 cells. In conclusion, the use of a modified AB for β-glucan from Saccharomyces cerevisiae exerted a promising antimicrobial, immunomodulatory efficacy, and anti-cancer potential. Future research should focus on evaluating β-glucan in various biological systems and elucidating the underlying mechanism of action.     

Adsorptive Stripping Voltammetric Determination of Imipramine and Amitriptiline at a Nanoclay Composite Carbon Ionic Liquid Electrode

A new carbon nanocomposite electrode has been designed by incorporation of montmorillonite nanoclay into a carbon ionic liquid electrode for the electrochemical determination of imipramine (IMP) and amitriptyline (AMT). They are expected to accumulate on the electrode surface through the cooperative interaction of ionic liquid and clay with the drugs. The proposed electrode also possesses attractive electrocatalytic effects towards the drugs especially AMT. Low detection limits of 19 nM for IMP and 24 nM for AMT were achieved. The proposed nanocomposite electrode exhibits good applicability for monitoring IMP and AMT in pharmaceutical formulations and blood serum samples.     

Shearing effects on the breathing mechanism of a cracked beam section in bi-axial flexure

The main purpose of this paper is to complete the works presented by Andrieux and Varé (2002) and El Arem et al. (2003) by taking into account the effects of shearing in the constitutive equations of a beam cracked section in bi-axial flexure. The paper describes the derivation of a lumped cracked beam model from the three-dimensional formulation of the general problem of elasticity with unilateral contact conditions on the crack lips. Properties of the potential energy and convex analysis are used to reduce the three-dimensional computations needed for the model identification, and to derive the final form of the elastic energy that determines the nonlinear constitutive equations of the cracked transverse section. We aim to establish a relation of behavior between the applied forces and the resulting displacements field vectors, which is compatible with the beams theory in order to allow the model exploitation for shafts dynamics analysis. The approach has been applied to the case of a cracked beam with a single crack covering the half of its circular cross section.