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Identifier 000032319
Title Ανάπτυξη νέων ποτενσιομετρικών αισθητήρων φωσφορικών ιόντων
Alternative Title Development of novel phosphate potentiometric sensors
Author Τσαγκατάκης, Ιωάννης Κ
Thesis advisor Χανιωτάκης, Νικόλαος
Abstract The development of novel phosphate potentiometric sensors based on the chemical recognition of phosphate using bidentate organotin compounds is presented. Phosphate is an essential component of various artificial products, especially detergents and fertilizers. The excessive use of these products contributes to serious environmental problems such as the eutrofication in rivers and lakes. On the other hand, phosphate is a component of nucleic acids and of adenosine phosphate compounds. This way phosphate participates in major biological processes. Inorganic phosphate is also essential for human life as component of blood and human bones. Thus, phosphate analysis is very important in environmental, pharmaceutical and clinical applications. Nowadays, the use of phosphate sensors in such applications is limited due to various sensior functional problems such as selectivity, reproducibility and lifetime. The objective of this work was to overcome the above problems in order to construct an effective phosphate sensor. Various organotin compounds were tested as phosphate carriers in polymer based IonSelective Electrodes (ISEs). Remarkable selectivity of bidentate organotin compounds towards phosphate was observed, which depends on the structure of the organotin compound. During the process of the phosphate carrier evalution the best selectivity towards phosphate was obtained by the carrier bis-(dichlorophenylstannyl)-methane.n Unfortunately, the ISEs based on this carrier showed poor reproducibility and short lifetime due to hydrolysis of the organotin carrier upon contact with water.In order to overcome these problems the influence of different membrane components in the ISE operation was studied. such componets were the plasticizer, the ionic aditives and the polymer. It was found that the use of plasticizer TEHP instead of DOS improves considerably the electrode lifetime. It was also observed that the use of plasticizer FP-NPE in combination with the polymer PVC-COOH gives phosphate ISEs with good functional characteristics, such as linear calibration curve to phosphate with detection limit of 1μΜ. Although after the membrane optimization process remarkable improvements on the develment of phosphate ISEs were achieved, the short electrode lifetime (few hours of continuous use) remained the greatest problem. For this reason a novel type of Solid-Contact ISEs (SC-ISEs) was developed. In this approach the ISE internal filling solution was a 5% (w/w) solution of the carrier bis-(dichlorophenylstannyl)-methane in plasticizer instead of the aqueous internal filling solution used in conventional ISEs. Two types of SC-ISEs were constructed: The SC-ISEs with conductive Carbon rod (CSC-ISEs) and the SC-ISEs with Liquid Membrane (LMSC-ISEs). The LMSC-ISEs constructed with the plasticizer FP-NPE had lifetime of fifteen days under continuous use. The electrode selectivity towards phosphate was very good. Linear calibration curves to phosphate in buffered solutions of pH=5.0 with a slope of 56mV/decade and a detection limit of 3.2x10^-6 M were obtained. The electrodes can be used in a pH range of 3-8. The electrode responded to phosphate concentration changes within i min. Stable potential values were obtained with a reproducibility of 3.7mV/concentration measurement. The LMSC-ISEs were also used in FIA measurements with great success. In the FIA mode the electrodes showed very good baseline return, while the reproducibility of peak height was of 2.4mV/concentration measurement. The results of this work were very important for the following reasons: i. A phosphate carrier was developed with the best selectivity towards phosphate that has ever been reported. ii. It was found that membrane components play a very important role in the electrode behavior. ISE membranes that had high compatibility with the organotin carrier were prepared and consequently the electrode characteristics were improved. iii. The development of the SC-ISEs was determinant for the remarkable improvement of the phosphate ISE lifetime and functional characteristics. Based on these findings the phosphatge sensors constructed will soon find applications in environmental and clinical analysis after minor optimizations. During this work novel organotin compounds as fluoride and chloride carriers in ISEs were also invented. Preliminary results have established the future successful construction of novel fluoride and chloride ISEs.
Language Greek
Subject Anion
Chemical recognition
Chloride
Fluoride
ISEs
Membrane
Organotin carriers
Phosphate
Potentiometric sensors
SC-ISEs
Selectivity
Ανιόν
Επιλεκτικότητα
Μεμβράνη
Οργανοκασσιτερικοί ιονομεταφορείς
Φθοριούχα
Φωσφορικά
Χλωριούχα
ποτενσιομετρικοί αισθητήρες
χημική αναγνώριση
Issue date 1999-07-01
Collection   School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
  Type of Work--Doctoral theses
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