Development of a Potentiometric Flufenamate ISE and its Application to Pharmaceutical and Clinical Analyses

Development of a Potentiometric Flufenamate ISE and its Application to  
Pharmaceutical and Clinical Analyses

A. O. Santini, H. R. Pezza, J. E. de Oliveira and L. Pezza∗
Instituto de Química, Universidade Estadual Paulista, CP 355, 14801-970 Araraquara-SP, Brazil

The characterist ics, performance, and application of an electrode, namely, PtHgHg2(FF)2Graphite, where FF stands for flufenamate ion, are described. This electrode responds to FF with sensitivity of (-58.6 ± 1.2) mV decade-1 over the range 1.0 × 10-6 - 1.0 × 10-2 mol L-1 at pH 6.0 - 9.0 and a detection limit of 7.1 × 10-7 mol L-1. The electrode is easily constructed at a relatively low cost with fast response time (within 10-25 s) and can be used for a period of 5 months without any considerable change in its performance characteristics. The proposed electrode displayed good selectivity for flufenamate in the presence of several substances as well as in the presence of some carboxylate and inorganic anions. The electrode was successfully applied to the determination of flufenamic acid in pharmaceuticals and human serum samples. 

Keywords: flufenamate-sensitive electrode, potentiometry, dosage forms, blood serum

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THEORY OF CONDUCTOMETRIC AND POTENTIOMETRIC TITRATION

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CONTENTS
1. TITRATION                                             3
2. CONDUCTOMETRIC TITRATION       5
3. POTENTIOMETRY                               14
 

            3.1 pH  measurements           14
            3.2 Potentiometric titration     16

 

 TITRATION

Titration is process of chemical analysis in which the quantity, amount or concentration, of some constituent of a sample, known as an analyte, is determined by adding to the measured sample an exactly known quantity of another substance with which the desired constituent reacts in a definite, known proportion. The process is usually carried out by gradually adding  a standard solution (i.e., a solution of known concentration) of titrating reagent, or  titrant, from a   burette, essentially a long, graduated measuring tube with a stopcock and a delivery  tip at its lower end. Titrations may be carried out by hand from the burette or automatically.

CONDUCTOMETRIC TITRATION

In this experiment we shall be concerned with electrical conduction through aqueous solutions. Although water is itself a  very poor conductor of electricity, the presence of ionic species in solution increases the conductance considerably. The conductance of such electrolytic solutions depends on the concentration of the ions and also on the nature of the ions present ( through their charges and mobilities ). Conductance behaviour as a function of concentration is different for strong and weak electrolytes.

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