Fenazopiridin Hidroklorür’ün İyonlaşma Sabitinin Analizi: Potansiyometrik Titrasyonda Üç Farklı Ekstrapolasyon Tekniğinin Kullanılması

Year 2014, Issue: 2, 147 - 157, 01.06.2014

Engin Koçak Mustafa Çelebier Sacide Altınöz

Abstract

Bu çalışmanın amacı potantisyometrik titrayondan elde edilen sonuçların değişik ekstrapolasyon yöntemleri ile değerlendirilerek iyonlaşma sabitlerinin bulunması ve bu ekstrapolsayon metodlarının karşılaştırılmasıdır. Suda az miktarda çözünebilen Fenazopiridin hidroklorür model molekül olarak seçilmiş ve çalışmalarda MDM metanol, asetonitril ve 1,4-dioksan – Su karışımları kullanılarak kosolvent iyonlaşma sabitleri hesaplanmıştır. Değişik oranlardaki MDM-Su karışımlarına 0.15M KCl eklenerek eşit iyonik kuvvet sağlanmıştır. Çalışmalarda 0.01M Sodyum hidroksit çözeltisi titrant olarak kullanılmış ve kosolvent iyonlaşma sabitleri belirlenmiştir. Sulu fazdaki iyonlaşma sabiti elde edilen deneysel veriler üç farklı ekstrapolasyon yöntemi ile hasplanmış ve karşılaştırılmıştır. Karşılaştırılan sonuçlar birbirinden çok farklı olamamakla birlikte litaratürde verilen sonuçlarla uyum içerisindendir.

Keywords

İyonlaşma sabiti, ekstrapolayon, Potansiyometri, Yasuda-Shedlovski, Fenazopiridin

Dissociation Constant Determination of Phenazopyridine Hydrocholoride: Using Three Different Extrapolation Techniques on Potentiometric Titration

Abstract

There are lots of publications reported about the biological activities of various synthesized compounds but it is rarely discussed the physicochemical properties of these substances as an additional/supporting data on biological activity. Acid dissociation constant is highly related with the ability or inability of the compounds to cross the cell membranes, and therefore it is a great importance to know the pKa of any potential active compound in order to classify and understand the behavior related with the permeability in the system of the body. Potentiometric titration is a well-known and easy to apply technique for determination of the dissociation constant of any ionized compound. The disadvantage of potentiometric titrations is that the concentration of the pharmaceutical solution must be high enough to indicate the equation point on analysis. It is not always possible to work with high concentrations if the compounds are slightly soluble in aqueous solutions. The application of MDM–water mixtures improves the solubility of poorly water soluble compounds, thus, their psKa values can be calculated easily in lower percentage of organic solvents. The aqueous pKa values could be easily obtained by using extrapolation techniques. The MDM–water mixtures do not cause large shifts on psKa values. In this study, the application of three different extrapolation techniques was shown by using pzp HCl as a model molecule and it was concluded that extrapolation results were very close to the reported pKa value of pzp HCl. Thus, it was shown that the extrapolation techniques could be easily applied for determination of the pKa values of any drug candidate molecule.

Keywords

ionization constant, extrapolation, potentiometry, Yasudashedlovski, phenazopyridine

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