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Determination of Vitamin D by Sensor Technologies Based on Molecular Imprinted Polymers
(Izmir Institute of Technology, 2022) Ölçer, Yekta Arya; Eroğlu, Ahmet Emin; Demir, Mustafa Muammer
Vitamin D is an essential nutrient in the body; it plays important roles in human health. Both its lack and excess can have health risks. As a consequence, there is a great demand for development of simple and precise detection methods for vitamin D derivatives in different samples. Molecular imprinting polymers (MIPs) are artificial receptors that can recognize target molecules in solution. In this study, two different polymerization techniques were used to obtain MIP/NIP sorbents/films for the detection of vitamin D3. Firstly, molecular imprinted solid phase extraction (MISPE) method was proposed prior to HPLC-DAD analysis. Optimized parameters were as follows; sorbent amount of 5.0 mg for 5.0 mL of 1.0 mg/L vitamin D3 in 90:10 (v/v) ratio of H2O:MeOH solution, 5 hours sorption time and MeOH:HOAc ratio of 90:10 (v/v) as desorption solution. The accuracy of the method was verified with spike recovery test for PBS:MeOH in a ratio of 90:10 (v/v) and overall recovery was found as 85.1 (±4.3, n=3). In latter case, a quartz crystal microbalance (QCM) method was proposed for determination of vitamin D3. Electrochemical polymerization of poly(4-vinylpyridine) MIP/NIP films were achieved on gold working electrode by cyclic voltammetry (CV). Mass-transfer ability of the polymer films were analyzed by electrochemical impedance spectroscopy (EIS). The electrochemical QCM (eQCM) was used to develop thin polymer films on quartz crystals and vitamin D3 determination was achieved by QCM. In a preliminary test, as small a concentration as 0.0100 mg/L vitamin D was detected with the QCM method.
Investigation of Carotenoid Contents of Various Microalgae by Chromatographis/Spectroscopic Methods
(Izmir Institute of Technology, 2013) Erdoğan, Ayşegül; Eroğlu, Ahmet Emin
Microalgae are the most important energy sources among microorganisms. Carotenoids, as important pigments and antioxidants, are produced by microalgae and are used both for health purposes and as natural colorants. There has been considerable research for the development, identification and determination of new strains of organisms to produce a variety of carotenoids. New methods for the isolation of carotenoids should be developed also for analytical purposes. This study aimed the biosynthesis of carotenoids from microalgae, (Prochlorococcus sp., Scenedesmus protuberans and Nitzschia sp.) their identification and quantification. It is known that some types of microalgae can produce high amount of carotenoids under different stress conditions while some others can produce carotenoids only under stress. For this purpose, cultivation conditions were optimized for the production of new or high value of carotenoids in the selected microalgal strains. Freeze-dried microalgae were extracted using different organic solvents and their carotenoid contents were investigated by high performance liquid chromatography (HPLC) and other chromatographic techniques such as liquid chromatography-mass spectrometry (LC-MS); in addition to (UV-VIS) spectroscopy. In green microalgae lutein (2.54 mg/g for Prochlorococcus sp. and 2.45 mg/g for Scenedesmus protuberans) is the most abundant carotenoid. On the other hand, in brown microalga fucoxanthin (6.58 mg/g for Nitzschia sp.) is the highly accumulated carotenoid. Under stress conditions, many microalgae alter their biosynthetic pathways for the formation and accumulation of carotenoids. Therefore, the effect of different nitrogen sources, oxidative stress conditions and different light sources on lutein content in green microalgae and on fucoxanthin content in brown microalga were investigated.

Phd Degree / Doktora

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