Analitik Kimya/Makale Koleksiyonu
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Öğe The development of forced degradation studies for the determination of daptomycin in urine at various conditions by using RP-LC method(MARMARA UNIV, 2019) Akmeşe, Bediha; Bakırhan, Nurgül K.; Göver, Tuğçe; Özkan, Sibel A.Daptomycin is known as the first lipopeptide antibiotic shows activity against gram-positive bacteria. A fast, simple and repeatabile RP-LC method has been developed for the determination of daptomycin in mobile phase solution and human urine. This drug was exposed to various stress conditions such as hydrolytic, oxidative, thermal and photolytic and the stressed samples were detected by the proposed method. Daptomycin was well separated on a X-Terra RP-18 column using the mobile phase consisting of a mixture of acetonitrile: water (45:55 v/v) at a flow rate of 1 mL min(-1). The system operates at 222 nm for daptomycin and 319 nm and tinidazole was used as internal standard under these conditions. The linearity of daptomycin was obtained between 0.50 and 12 mu g mL(-1) concentration range. Limits of detection was determined as 0.1176 and 0.1412 mu g mL(-1) and the limits of quantification was obtained as 0.3563 and 0.4277 mu g mL(-1) in the mobile phase and urine, respectively. Hydrochloric acid, sodium hydroxide, hydrogen peroxide affected response of daptomycin under stress degradation conditions.Öğe Degradation studies and thermodynamic parameters in aqueous solution of chemotherapeutic agents: Daunorubicin, doxorubicin and vincristine(MARMARA UNIV, 2019) Bakırhan, Nurgül Karadaş; Akmeşe, Bediha; Göver, Tuğce; Imanzadeh, Hamideh; Özkan, Sibel A.The degradation of daunorubicin (DNR), doxorubicin (DXR) and vincristine (VCR) as chemotherapeutic agents was investigated under stress conditions such as acidic and alkaline media, oxidation, photolytic and heating. The degradation pathway determined by high-performance liquid chromatography (HPLC). Daunorubicin, doxorubicin and vincristine completely disintegrated in the basic medium. It has been determined that these drugs are resistant to heat. Daunorubicin and doxorubicin are resistant to UV light. However, vincristine is not very stable such as the other two compounds against UV light. The kinetic and thermodynamic parameters of daunorubicin, doxorubicin and vincristine were investigated in neutral media with different temperatures by electrochemical technique. Enthalpy, entropy and Gibbs free energy parameters were investigated in pH 7.4 phosphate buffer (PB) solution due to stability of these drugs at this pH. The studied chemotherapeutic agents showed endothermic process on glassy carbon-based electrode surface. Daunorubicin, doxorubicin and vincristine showed strongly adsorption process in room temperature. However, it showed diffusion property from electrode to solution with increasing the temperature values.Öğe The Effect of Accompanying Anion and the Competitive Transport of Ni(Ii) and Fe(Iii) Through Polysulfone Membranes(Marcel Dekker Inc, 2003) Kır, Esengül; Tor, Ali; Çengeloğlu, Yunus; Ersöz, MustafaThe effect accompanying anion on the transport of Ni2+ and competitive transport of Ni2+ and Fe3+ ions through charged polysulfone or polysulfone polyester-supported cation exchange membranes was studied under Donnan dialysis conditions. In the Donnan dialysis process, two electrolyte solutions were separated by ion permeable membrane, the one side (feed solution) initially containing metal salts or their mixtures, the other is HCl and no external potential field is applied. The transport of metal ions through membranes was correlated with the efficiency factor (EF) values as well as with fluxes and depended on the interaction between the fixed groups in the membrane and the metal ions. The EF value of Ni2+ as a single as well as mixture state was higher than that of Fe3+ for both types of membranes. The effect of accompanying anion on the transport of Ni2+ was found to be in the following order of Cl- > NO3- > SO4-2, and the results were correlated with the EF values, as well as with the membrane structure.Öğe Transport of Amino Acids Through Charged Cation-exchange Membrane(INST ORGANIC CHEM AND BIOCHEM, 2001) Kara, H; Yazicigil, Zafer; Durmaz, Fatih; Ersoz, MustafaThe sorption and transport of amino acids such as glycine, L-valine and L-leucine through charged polysulfone membranes was investigated as a function of pH lower than 5.6 under three different interfacial conditions. The sorption was characterized by the Langmuir and the Freundlich equations. The highest permeability was obtained if the initial pH on the amino acid source side was 5.6 and that on the opposite side 2.5, the intermediate permeability was obtained if the initial pH on both sides was 2.5, and the smallest permeability was obtained if the initial pH on the amino acid side was 5.6. The obtained results are explained in terms of the interfacial transport based on the chemical reaction (protonation and ion exchange).
