Giray Topal

Preparation of a novel ionic hybrid stationary phase by non-covalent functionalization of single-walled carbon nanotubes with amino-derivatized silica gel for fast HPLC separation of aromatic compounds.

Single-walled carbon nanotubes (SWCNTs) were immobilized on spherical silica gel with a 4-μm average particle size and a 60-Å average pore size. The amino-derivatized silica gel was non-covalently coated with carboxylated SWCNTs to preserve the structure of the nanotubes and their physico-chemical properties. The novel ionic hybrid stationary phase was characterized by scanning electron microscopy (SEM), infra-red (IR) spectroscopy and elemental analysis, and then, it was used to fill an empty 150×4.6mm(2) high-performance liquid chromatography (HPLC) column. Chromatographic parameters, such as the theoretical plate number, retention factor and peak asymmetry factor, and analytical parameters, such as the limit of detection (LOD), limit of quantification (LOQ), linear range, calibration equation, and R(2) value, and quantitative analysis parameters were calculated for all of the analytes. Using different mobile phases, five different classes of aromatic hydrocarbons were separated in a very short analysis time of 4-8min. Furthermore, a high theoretical plate number (up to 25000) and an excellent peak asymmetry factor (1.0) were obtained. The results showed that the surface of the SWNTs had very strong interactions with aromatic groups, therefore providing high selectivity for the separation of different classes of aromatic compounds. This study indicates that SWCNTs enable the extension of the application range of the newly prepared stationary phases for the fast separation of aromatic compounds by HPLC.

Resolution of (±)-β-methylphenylethylamine by a novel chiral stationary phase for Pirkle-type column chromatography

In this study, a new Pirkle-type chiral column stationary phase for resolution of beta-methylphenylethyl amine was described by using activated Sepharose 4B as a matrix, L-tyrosine as a spacer arm, and an aromatic amine derivative of L-glutamic acid as a ligand. The binding capacities of the stationary phase were determined at different pH values (pH = 6, 7, and 8) using buffer solutions as mobile phase, and enantiomeric excess (ee) was determined by HPLC equipped with chiral column. The ee was found to be 47%.

Enantioseparation of Mandelic Acid Enantiomers With Magnetic Nano-Sorbent Modified by a Chiral Selector

In this study, R(+)-α-methylbenzylamine-modified magnetic chiral sorbent was synthesized and assessed as a new enantioselective solid phase sorbent for separation of mandelic acid enantiomers from aqueous solutions. The chemical structures and magnetic properties of the new sorbent were characterized by vibrating sample magnetometry, transmission electron microscopy, Fourier transform infrared spectroscopy, and dynamic light scattering. The effects of different variables such as the initial concentration of racemic mandelic acid, dosage of sorbent, and contact time upon sorption characteristics of mandelic acid enantiomers on magnetic chiral sorbent were investigated. The sorption of mandelic acid enantiomers followed a pseudo-second-order reaction and equilibrium experiments were well fitted to a Langmuir isotherm model. The maximum adsorption capacity of racemic mandelic acid on to the magnetic chiral sorbent was found to be 405 mg g(-1). The magnetic chiral sorbent has a greater affinity for (S)-(+)-mandelic acid compared to (R)-(-)-mandelic acid. The optimum resolution was achieved with 10 mL 30 mM of racemic mandelic acid and 110 mg of magnetic chiral sorbent. The best percent enantiomeric excess values (up to 64%) were obtained by use of a chiralpak AD-H column.

Synthesis and Physicochemical Characterization of Chitin Derivatives

Firstly, chitin derivatives were synthesized. For this purpose, chitin was modified via ring-opening reaction with cyclic anhydrides in lithium chloride/N,N-dimethylacetamide. Then, chitin derivatives synthesized were characterized by FTIR, 1H NMR, 13C NMR, and U-Vis spectroscopies and scanning electron microscopy. Thermogravimetric analysis was performed to investigate the thermal stability of chitin derivatives. Thermogravimetric analysis results showed that chitin modified with trimellitic anhydride is thermally more stable than chitin modified with phthalic anhydride. In addition, the electrical conductivity of chitin modified with phthalic anhydride and trimellitic anhydride was also measured. Electrical conductivity measurement results showed that the electrical conductivity of chitin modified with trimellitic anhydride (1.2×10−4 S cm−1) is higher than that of chitin modified with phthalic anhydride (9.2×10−5 S cm−1).

SYNTHESIS AND COMPLEXATION OF NEW SUBSTITUTED DIBENZODIAZA MACROCYCLIC DIESTER COMPOUNDS

ABSTRACT The synthesis of some new precoursers that contain substituted benzo units and their use in the preparation of azamacrocyclic diester compounds are reported. These precoursers and ligands were characterized by Elemental analysis, 1H and 13C NMR spectroscopy, and IR spectroscopy. The complexation constants Ke and ΔG° values for the diesters with several transition metal cations (Ag+, Zn2+ and Cu2+) in a dioxan–water system using a conductometric method at 25°C are also reported.

PREPARATION OF NEW o-CARBOXYANILINOTELLURIUM(IV) BROMIDES AND THEIR DYEING PROPERTIES

This study represents a new synthesis of two organotellurium compounds and their dyeing properties. The structure of these tellurium derivatives are proposed based on elemental analyses, IR, UV-Vis, 1H and 13C NMR spectra and thermogravimetric analyses (TGA).

Diester Molecules for Organic-Based Electrical and Photoelectrical Devices

Diester derivatives of terephthalic acid molecules were synthesized according to the literature. Au/Diester derivatives/n-Si organic–inorganic (OI) heterojunction-type devices were fabricated, and the current–voltage (I–V) characteristics of the devices have been investigated at room temperature. I–V characteristics demonstrated that all diodes had excellent rectification properties. Primary diode parameters such as series resistance and barrier height were extracted by using semi-log I–V plots and Norde methods, and were compared. It was seen that there was a substantial agreement between results obtained from two methods. Calculated barrier height values were about the same with 0.02-eV differences that were attributed to the series resistance. Ideality factors, which show how the diode closes to ideal diodes, were also extracted from semi-log I–V plots. Thus, the modification of the Au/n-Si diode potential barrier was accomplished using diester derivatives as an interlayer. The I–V measurements were repeated to characterize the devices at 100 mW/cm2 illumination intensity with the help of a solar simulator with an AM1.5G filter.

Synthesis, characterization, and Schottky diode applications of low-cost new chitin derivatives

In this study, low-cost two new chitin derivatives were first synthesized. Products formed in the consequence of the reaction of chitin with 4-nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride were named C4NC and C35DC, respectively. Then, C4NC and C35DC were characterized by FTIR and 13C CP-MAS solid-state NMR spectroscopies and X-ray powder diffraction technique. Surface topography and composition of C4NC and C35DC with a scanning electron microscope were investigated. Mass loss in C4NC and C35DC with thermogravimetric analysis method was determined as a function of increasing temperature. Endothermic and exothermic transitions in C4NC and C35DC were investigated with differential thermal analysis and differential scanning calorimetry techniques. Later on, charge carrier density, hole mobility, and electrical conductivity values of C4NC and C35DC were determined. Besides, Schottky diodes of C4NC and C35DC were constructed, and several parameters related to these diodes were determined. Finally, the sensitivity of these diodes to light was studied.

THE PREPARATION OF A NEW PROTEIN BASED HPLC COLUMN PACKING MATERIAL AND ENANTIOMERIC RESOLUTION OF SOME PHARMACEUTICAL RELATED COMPOUNDS VIA THIS COLUMN

In this study, BSA was bounded to 3-chloropropyl functionalized silica gel via ethylenediamine and glutaric dialdehyde. The prepared CSP was packed into 150X4.6mm HPLC column according to slurry method. The enantiomeric resolution of some pharmaceutical related compounds such as rac-mandelic acid, rac-methyl mandelate, rac-epinephrine, rac-propranolol, rac-α-phenylethylamine and rac-3-hydroxybutyric acid was employed in 1mL/rpm, 1,5mL/rpm, 2mL/rpm, 2,5mL/rpm, 3mL/rpm flow rate in various pHs such pH=6, pH=7, pH=8 0,1M phosphate buffer. Chromatographic parameters such as Rs and α were calculated for each resoluted compounds.