Plastic Membrane Electrodes of Coated Wire Type for Micro Determination of Quininium Cation in Pharmaceutical Tablets

Abstract

Problem statement: Silver and copper all-solid state wire sensor electrodes of quininium cation with different ion exchangers have been prepared and used in pharmaceutical analysis. A comparative study with a reference method is applied in order to investigate the validity of the proposed method for potentiometric analysis of pharmaceutical compounds containing quinine. Approach: A Nernstian equation was proved for all electrodes of quinine in this research. Potentiometric investigations were carried out to identify the characteristic performance of the electrodes, such as the life span, pH effect and effect of the interfering ions. Chemometric and statistical studies of the chemical analysis of quinine in pharmaceutical compounds were applied using different type of electrodes compared to a reference method. Results: A Polyvinyl Chloride (PVC) membrane electrodes of silver (Ag) and Copper (Cu) Coated Wire Electrodes (CWEs) were prepared for quininium cation (Qn⁺). The ion exchangers were ion-pairs and ion associates of Qn+ with different counter-anions, such as reineckate (Rn^-), phosphotungstate (PT^3-) and phosphomolybdate (PM^3-). The Qn-CWEs showed a Nernstian response for a maximum 24 h at 25°C, except with that based on Cu- Qn₃PM.Conclusion/Recommendations: The ion pair QnRn and the ion associates Qn₃PT and Qn₃PM are very efficient ion exchangers for the construction of Qn-CWEs. The performance characteristics (life span, pH effect and the selectivity) proved that such electrodes can be successfully used for the potentiometric micro-determination of Qn₂SO₄ in its pharmaceutical preparation. The analytical application showed that the recoveries and relative standard deviation of different Qn-CWEs reveals a high degree of accuracy and precision. In spite of their high accuracy, the F- test conclude the fact that the reference method is usually more precise than proposed method introduced in this study except for Ag-Qn₃PM electrode. In general, Ag-Qn₃PM CWE showed a discrete behavior regarding accuracy and silver metal preference. Further application of this type of electrodes on different pharmaceutical compounds is recommended to countervail the trends on the performance characteristics and confront the statistical parameters.