Osman Cubuk

Experimental and theoretical study on the structure and vibrational spectra of β-2-aminopyridinium dihydrogenphosphate

Experimental and theoretical vibrational spectra of β-2-aminopyridinium dihydrogenphosphate (β-2APDP) have been investigated. The FT-IR spectrum of β-2APDP was recorded in the region 4000-400 cm(-1). The optimized molecular structure and theoretical vibrational frequencies of β-2APDP have been investigated using ab initio Hartree-Fock (HF) and density functional B3LYP method with 6-311++G(d,p) basis set. The optimized geometric parameters (bond lengths and bond angles) and theoretical frequencies have been compared with the corresponding experimental data and it is found that they agree well with each other. All the assignments of the theoretical frequencies were performed by potential energy distributions using VEDA 4 program. Furthermore, the used scale factors were obtained from the ratio of the frequency values of the strongest peaks in the experimental and theoretical IR spectra. From the results it was concluded that the B3LYP method is superior to the HF method for the vibrational frequencies.

PVC-Membrane Potentiometric Sensor for the Determination of Tamoxifen in Pharmaceutical Formulations

Novel tamoxifen-selective potentiometric electrodes based on various ion associations of tamoxifen were developed. The most suitable membrane composition, which has the best potentiometric characteristics, was examined under steady-state conditions. The membrane composed of (w/w) 3% tamoxifenphosphomolibdate ion pair, 32% poly(vinylchloride), and 65% 2-nitrophenyloctylether was determined as the membrane with the best analytical properties. On the condition of pH = 2-6, the fabricated electrode exhibited linear responses over the concentration range of 9.1 × 10-6 -1 × 10-3 M tamoxifen solutions (R2 = 0.9989) with a sensitivity of 42.9 ± 0.3 mV/decade, detection limit of 7.3 ± 0.4 × 10-6 M and short response time of ≈25 s. The influences of some alkaline, alkaline earth metals, biologically significant molecules, and some pharmaceutical species over electrode responses were studied. The proposed electrode was applied for the determination of tamoxifen contents of some pharmaceutical formulations by using standard addition method. The potentiometric analysis results obtained for the pharmaceutical formulations were in good harmony with the results obtained by high performance liquid chromatography at 95% confidence level.

Electrochemical Determination of Copper(II) in Water Samples Using a Novel Ion-Selective Electrode Based on a Graphite Oxide–Imprinted Polymer Composite

ABSTRACT A novel copper(II)-selective electrode based on graphite oxide/imprinted polymer composite was developed for the electrochemical monitoring of copper(II) (Cu2+) ions. The electrode exhibited highly selective potentiometric response to Cu2+ with respect to common alkaline, alkaline earth and heavy metal cations. The composite composition studies indicated that the most suitable composite composition performing the most promising potentiometric properties was 20.0% ionophore (Cu2+-ion imprinted polymer), 10.0% paraffin oil, 5.0% multiwalled carbon nanotubes, and 65.0% graphite oxide. The fabricated electrode exhibited a linear response to Cu2+ over the concentration range of 1.0 × 10− 6–1.0 × 10− 1 M (correlation coefficient of 0.9998) with a sensitivity of 26.1 ± 0.9 mV decade− 1. The detection limit of the fabricated electrode was determined to be 4.0 × 10− 7 M. The electrode worked well in the pH range of 4.0–8.0. The electrode had stable, reversible and fast potentiometric response (3 s). In addition, the electrode had a lifetime of more than 1 year. The analytical applications of the proposed electrode were performed using as an indicator electrode for the potentiometric titration of Cu2+ with ethylene diamine tetraacetic acid solution and for the determination of Cu2+ of spiked river, dam, and tap water samples. The obtained results for potentiometric titration and water samples were satisfactory.

Structural, thermal and morphological properties of a novel poly(acrylamide-co-methacrylic acid)/organoclay nanocomposite

ABSTRACT A novel poly(acrylamide-co-methacrylic acid)/organoclay nanocomposite was prepared and its structural, thermal, and morphological properties were investigated by various techniques. The absence of diffraction peaks for the organomodified-smectite nanocomposite showed that dispersion of the clay nanolayers within the polymer matrix was in the form of an exfoliated nanostructure. Morphological studies confirmed that organomodified-clay dispersed homogeneously in the polymer matrix. Infrared spectroscopy results indicated that the organosmectite is physically dispersed in the polymer network without forming any chemical bonds. The thermal analysis data revealed that there are significant increases in temperatures of decomposition and softening points of polymer with addition of organoclay.

Key words: Sound Diffraction; Lined Duct; Integral Transform; Wiener-Hopf Technique; Expansion Coefficients; Pole Removal Technique

The intercalation of dimethyl sulphoxide (DMSO), pyridine (Py), ethanolamine (Ea), and Nmethyl formamide (NMF) molecules into the kaolinite interlayers led to an appreciable decrease of 3697 cm−1 of the hydroxyl band. The appearance of the peaks at 3662, 3541, and 3504 cm−1 proved that the DMSO species are intercalated between the kaolinite layers through forming H-bonds with internal-surface hydroxyl groups. The intensities of the 942 and 796 cm-1 bending peaks arising from inner-surface hydroxyls decreased and new vibrational features appeared due to the intercalation of the guest species. The d001 value of pure kaolinite was found at 7.18 A° , and the d001 values were seen at 11.26, 11.62, 10.77, and 10.67 °A for kaolinite-dimethyl sulphoxide (K-DMSO), kaolinite-pyridine (K-Py), kaolinite-ethanolamine (K-EA), and kaolinite-N-methyl formamide (K-NMF) composites, respectively. The endothermic differential thermal analysis (DTA) peaks at a temperature of 108 - 334 ◦C reflected the changes in the physicochemical properties of the intercalated species. The thermal stability increase followed the order of K-Py<K-NMF<K-Ea<K-DMSO. Based on the thermal analysis data, the intercalation ratios of the composites above were determined as 80.0, 40.0, 81.6, and 82.0%, respectively. The specific surface areas are affected by the intercalation geometry of the composites within the gallery spacing. The surface areas of the K-DMSO, K-Py, and K-EA complexes increased whereas the surface area of K-NMF decreased with respect to that of untreated kaolinite.

ASİT AKTİFLEŞTİRİLMİŞ BENTONİT (ÜNYE) NUMELERİNDEKİ ASİDİK MERKEZLERİNİN TEŞHİSİ

Based on the intensitive peaks at 1540 cm-1 and 1450 and 1610-1605 cm -1 of adsorbed pyridine species, the Bronsted acidities of the samples are given as 6A->8A->4A->2A->10A bentonite. The surface area reached a