Ayça Demirel Özel

Development of a pH sensing membrane electrode based on a new calix[4]arene derivative.

A new pH sensing poly(vinyl chloride) (PVC) membrane electrode was developed by using recently synthesized 5,17-bis(4-benzylpiperidine-1-yl)methyl-25,26,27,28-tetrahydroxy calix[4]arene as an ionophore. The effects of membrane composition, inner filling solution and conditioning solution on the potential response of the proposed pH sensing membrane electrode were investigated. An optimum membrane composition of 3% ionophore, 67% o-nitrophenyl octyl ether (o-NPOE) as plasticizer, 30% PVC was found. The electrode exhibited a near-Nernstian slope of 58.7±1.1 mV pH(-1) in the pH range 1.9-12.7 at 20±1 °C. It showed good selectivity for H(+) ions in the presence of some cations and anions and a longer lifetime of at least 12 months when compared with the other PVC membrane pH electrodes reported in the literature. Having a wide working pH range, it was not only applied as a potentiometric indicator electrode in various acid-base titrations, but also successfully employed in different real samples. It has good reproducibility and repeatability with a response time of 6-7s. Compared to traditional glass pH electrode, it exhibited excellent potentiometric response after being used in fluoride-containing media.

PVC-membran elektrotların performansına plastikleştirici ve iletkenlik arttırıcıların etkisi

Analitik kimyada bir turun matriks ortaminda dogru ve kesin tayini cok onemlidir. Numunelerde mevcut eser turlerin tayini icin genellikle cok pahali ve karmasik cihazlar kullanilmaktadir. Halbuki elektrotlarla tayin, hem daha pratik hem de daha ucuz olmaktadir. Bu durumda cok sayida ture duyarli ve secici elektrotlarin hazirlanmasi ve cesitli matriks ortaminda turlerin tayininin yapilabilmesi icin yontem gelistirilmesi oldukca onemli hale gelmektedir. Bu projede notral tasiyici (iyonofor) olarak makrosiklik bilesikler kullanilarak cesitli iyonlara duyarli bir cesitli PVC-elektrotlar gelistirilmesi amaclanmistir. Bu elektrotlarin omru, cevap suresi, optimum calisma araligi ve diger bazi cevap karakteristikleri arastirilmistir. Hazirlanan bu tip elektrotlarin membrani, iyonofor yaninda polimerik madde, plasiklestirici ve iletkenlik arttirici gibi bir matriks icermektedir. Matriks icinde bulunan bu bilesenlerin, ozellikle de plasiklestirici ve iletkenlik arttirici cinsinin ve oranlarinin membranin performansina etkisi oldukca fazladir. Nernst cevabi elde edilen elektrot hazirlandiginda, bunun calisma araligi, cevap suresi, omru gibi cesitli parametreler belirlenmistir. Hazirlanan elektrodun tayin edilecek iyon disinda diger iyonlara duyarligi tespit edilerek cesitli yontemlerle bu katyonlar icin elektrodun secicilik katsayilari hesaplanmistir. Ayrica hazirlanan bu elektrodun cesitli analitik amaclar icin, kullanilip kullanilamayacagi da incelenmistir. AbstractThe determination of a species in a matrix media is very important in analytical chemistry. There are expensive and sophisticated equipment used in the detection of the trace species present in the samples. These type of determinations can be made both cheap and practical by the use of electrodes. Therefore development of techniques with the use of the electrodes sensitive to the certain species in different matrix is of great importance. The goal of this project is the construction of ion sensitive electrodes with the use of neutral carriers (ionopheres). The lifetime, response time, optimum working range and other response characteristics of these electrodes were also be investigated. The membrane of these electrodes contains a matrix made of a polymeric material, plasticiser and conductive material as well as an ionophere. The type and the ratio of the material present in the matrix have an important effect upon the performance of the electrode. In this study an electrode with Nerstian behaviour has been constructed and its working range, response time and other parameters were evaluated. The selectivity of the electrode towards the ion of the interest and towards other ions was deduced and the selectivity coefficients of the electrode towards various anions was computed. The suitability of the electrode prepared for various analytical purposes was also evaluated.