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New modified polymeric electrodes selective to local anaesthetic compounds.
A A Bouklouze1, A el-Jammal, G J Patriarche
1Institute de Pharmacie, Universite Libre de Bruxelles, Belgium.
Journal of Pharmaceutical and Biomedical Analysis
|January 1, 1991
Summary
New polymeric electrodes were developed for detecting local anesthetics like tetracaine, lidocaine, and procaine. These electrodes, utilizing phosphotungstic acid, offer accurate measurements in pharmaceutical preparations.
Area of Science:
- Electrochemistry
- Materials Science
- Analytical Chemistry
Background:
- Development of ion-selective electrodes (ISEs) is crucial for analyzing pharmaceutical compounds.
- Existing methods for local anesthetic detection may lack sensitivity or specificity.
- Polymeric electrodes offer potential for improved performance and versatility.
Purpose of the Study:
- To construct and characterize novel polymeric electrodes for the selective detection of tetracaine (TC), lidocaine (LD), and procaine (PC).
- To evaluate the performance of electrodes based on different ion-pairing agents and plasticizers.
- To assess the applicability of these electrodes for direct potentiometric determination in pharmaceutical formulations.
Main Methods:
- Incorporation of ion-pair complexes of TC, LD, and PC with phosphotungstic acid into ethylene-vinyl acetate (E/VAC) copolymer.
- Investigation of silicotungstate and tetraphenylborate as alternative ion-pairing agents.
- Optimization of plasticizer composition using a mixture of dioctyl phthalate (DOP) and nitrobenzene (NB).
- Electrochemical characterization including response linearity, Nernstian behavior, and pH influence.
Main Results:
- Electrodes incorporating phosphotungstic acid exhibited the best linear and Nernstian responses.
- Linear detection ranges were established for TC (10^-2–5.6 x 10^-6 M), LD (10^-2–2.5 x 10^-5 M), and PC (10^-2–1.8 x 10^-5 M).
- Electrode performance remained stable across a wide pH range for each compound.
- Minimal interference was observed from most organic base and alkali metal cations, with TC showing higher selectivity.
Conclusions:
- Novel polymeric electrodes based on phosphotungstate ion-pairs demonstrate effective potentiometric sensing for TC, LD, and PC.
- The developed electrodes offer good selectivity and stability, suitable for pharmaceutical analysis.
- Direct potentiometry provides accurate results for determining these local anesthetics in drug preparations.