Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
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Article Citation - WoS: 23Citation - Scopus: 26Development of Practical Hplc Methods for the Separation and Determination of Eggplant Steroidal Glycoalkaloids and Their Aglycones(Taylor and Francis Ltd., 2008) Eanes, Ritchie C.; Tek, Neslihan; Kırsoy, Öyküm; Frary, Anne; Doğanlar, Sami; Almeida, Adelia E.A practical set of HPLC methods was developed for the separation and determination of the eggplant steroidal glycoalkaloids, solanine, chaconine, solasonine, solamargine, and their aglycones, solasodine and solanidine. A gradient method was initially developed, but proved to be neither robust nor practical. Three separate isocratic methods using acetonitrile and ammonium dihydrogen phosphate were developed and shown to be more repeatable, less subject to fluctuations in mobile phase composition, and less time consuming. The effect of adjusting buffer pH, column temperature, and buffer type (triethylammonium phosphate vs. ammonium dihydrogen phosphate) were evaluated. It was also discovered that, by addition of 10% methanol to the acetonitrile portion of the mobile phase, more control over the separations was possible. The use of methanol as a mobile phase entrainer greatly improved separations in some cases and its effectiveness was also dependent upon column temperature. Assessments of the method recovery, limit of detection, and limit of quantitation were made using extracts from S. melongena and S. linnaeanum.Article Citation - WoS: 2Citation - Scopus: 2Solid-Phase Microextraction (spme) Followed by On-Fiber Derivatization of Solasodine and Solanidine Aglycones of Steroidal Glycoalkaloids(Taylor and Francis Ltd., 2008) Eanes, Ritchie C.; Tek, NeslihanSolid-phase microextraction (SPME), followed by on-fiber derivatization was investigated for the analysis of the steroidal glycoalkaloid aglycones, solasodine and solanidine. The aglycones were first extracted by direct immersion of the SPME fiber in the sample medium and then derivatized on the fiber in a separate step using 1-(trimethylsilyl)imidazole (TMSI). The derivatized compounds were then desorbed from the SPME fiber and detected by GC-MS. Polydimethylsiloxane/Divinylbenzene (PDMS-DVB), Carboxen/ Polydimethylsiloxane (CAR-PDMS), and Carbowax/Divinylbenzene (CW-DVB) fibers were employed with the CW-DVB fibers being the most successful, as expected. Closed-end capillary tubes were used to hold the extraction media. Both aglycones were successfully extracted, derivatized, and detected by GC-MS. Solasodine always required derivatization, but solanidine did not. The same method was successfully applied to cholesterol so that it could be used as an internal standard. Also, using the closed-end capillary tubes, a two-phase extraction system was also investigated, whereby the fiber was only exposed to the phase in which it was presumed to be less damaged. However, in all cases, fiber degradation was significant, preventing the use of extended extraction times and limiting reuse of the fibers. However, the results represent a first look into the feasibility of the method. With the development of more suitable SPME phases, this method could potentially provide a complementary route for routine determinations of glycoalkaloids for both research and food quality control.Article Citation - WoS: 4Citation - Scopus: 5Crystal Structure of Distrontium Manganese (iii) Tetraoxophosphate Heptaoxodiphosphate, Sr2mn[po4] [p2o 7](Walter de Gruyter GmbH, 2007) Doğan, Leyla; Eanes, MehtapMnO11P3Sr2, monoclinic, P121/c1 (no. 14), a = 6.641(1) Å, b = 6.834(1) Å, c = 19.554(4) Å, β = 99.22(3)°, V = 876.0 Å3, Z = 4, Rgt(F) = 0.051, wRref(F2) = 0.090, T = 298 K.Article Citation - WoS: 6Citation - Scopus: 6Crystal Structure of Lead(ii) Trioxovanadate(v) Chloride, Pb[vo 3]cl(Walter de Gruyter GmbH, 2007) Şahin, Aytaç; Eanes, MehtapClO3PbV, orthorhombic, Pnma (no. 62), a = 10.022(2) Å, b = 5.288(1) Å, c = 7.171(1) Å, V= 380.0 Å3, Z = 4, Rgt(F) = 0.035, wRref(F2) = 0.105, T= 153 K.Conference Object Citation - WoS: 2Citation - Scopus: 2Effects of Mechanical Treatment on the Formation of Α-Al 2o3 From Gibbsite(Trans Tech Publications, 2004) Şakar Deliormanlı, Aylin; Çiftçioğlu, Muhsin; Polat, HürriyetIn this study preparation of fine alpha alumina powders derived from Bayer gibbsite was studied. Preparation of the alumina powders was performed by decomposition of the gibbsite into transition alumina phase followed by controlled transformation to the alpha phase. Gibbsite was thermally treated at 350°C and 900°C to obtain a transition form of alumina. The purpose of the heat treatment at 350°C was to increase the surface area of the gibbsite particles and obtain a loosely packed structure that may reduce the size of the rather coarse precursor gibbsite during the grinding step. Mechanical treatment (by using ultrasonic forces and impact forces) was utilized to increase the transformation rate to the alpha alumina in the transition phase matrix and influence the nucleation and growth rate of the solid -solid phase transformation. These powders were calcined at 1100, 1200 and 1450°C for 1 to 8 hours. Results indicated that transformation to the alpha phase was accomplished in the powders preheated at 900°C, ultrasonically treated or ground, and then calcined at 1200°C for 2 to 8 hours or at 1450°C for 2 hours. Ultrasonic treatment accelerated the transformation rate to the alpha phase at 1100°C in 2 hours. Powders that were calcined at 1100 to 1200°C for 1 hour had a significant kappa content together with the alpha phase. Additionally the powder prepared without mechanical treatment and calcined at 1100°C was mainly in the kappa phase.Article Citation - WoS: 2Citation - Scopus: 2Redetermination of the Crystal Structure of Sodium Trisamarium Digermanate Dihydroxide, Nasm3(geo4)2(oh)2(Walter de Gruyter GmbH, 2002) Eanes, MehtapGe2H2NaO10Sm3, monoclinic, C12/c1 (No. 15), a = 18.323(3)Å, b = 5.2369(8) Å, c = 12.108(2) Å, β= 131.230(2)°, V = 873.8 Å3, Z = 4, R gt(F) = 0.037, wRref(F2) = 0.010, T= 153 K.Article Citation - Scopus: 15Estimation of the Average Aromatic Cluster Size Based on Solid-State Nmr Measurement of Coal(Japan Institute of Energy, 1999) Kidena, Koh; Murata, Satoru; Artok, Levent; Nomura, MasakatsuMeasurements of solid-state NMR of eight Argonne Premium Coal Samples were conducted to estimate the average aromatic cluster size in these coals. Firstly, the carbon distribution was obtained from SPE/MAS 13C-NMR. Secondary, 1H-CRAMPS NMR spectra gave the hydrogen aromaticity of coal. Combination use of the hydrogen aromaticity and elemental analysis data could afford the amount of tertiary aromatic carbon. The parameter of χ b, the mole fraction of aromatic bridgehead carbons in all aromatic carbons, could be derived from above NMR data and elemental analysis of coal. χ b is directly correlated to the number of aromatic carbon atoms per aromatic cluster, C. In this study, the value of C varied from 10 (corresponding to the size of naphthalene) for Beulah-Zap and Wyodak coals to 23 (corresponding to the size of coronene) for Pocahontas No. 3 coal.