Abstract
A flow-injection coulometric method for the determination of chlorpromazine based on ion transfer into a plasticized poly(vinyl chloride) (PVC) membrane, was developed. The detector used consists of a flow-through cell that incorporates a plasticized poly(vinyl chloride) (PVC) membrane which contains tetrabutylammonium tetraphenylborate as electrolyte. The membrane is located between the flowing solution and an inner aqueous electrolyte solution. Two pairs of electrodes, each pair formed by a reference electrode and a working electrode, are used, one pair in each solution. The potential between the reference electrodes was controlled by a four-electrode potentiostat with ohmic drop compensation. A potential step capable of producing the transfer of the chlorpromazine ion into the membrane was applied during the passage of a wide portion of sample plug through the cell and the corresponding quantity of the electricity was measured. In the selected conditions, a linear relationship was observed between the quantity of electricity and chlorpromazine concentrations over a range of 1×10-6 −1×10-4 M. The detection limit was 2 × 10-7 M. Good repeatability and between-day reproducibility was obtained. No interference was observed on the part of some common ions and pharmaceutical excipients. The method proposed was applied satisfactorily to the determination of chlorpromazine in pharmaceuticals and human urine.
Highlights
Ion transfer across the Interface between Two Immiscible Electrolyte Solutions (ITIES) is a fundamental aspect of the Electrochemistry of Liquid-Liquid Interfaces and several reviews [1,2,3] deal with its fundamentals, methodology and applications
At time t1 (Fig.1), when the central portion of the sample plug had arrived in the detector cell, a forward potential E1 capable of causing the transfer of protonated chlorpromazine cation into the membrane was applied for a duration ∆t1 = t2 −
In view of the results found in previous papers on amperometric methods based on ion transfer across a water-plasticized polymeric membrane interface [11,12], the interference of the pharmaceutical compounds imipramine and verapamil is expected
Summary
Ion transfer across the Interface between Two Immiscible Electrolyte Solutions (ITIES) is a fundamental aspect of the Electrochemistry of Liquid-Liquid Interfaces and several reviews [1,2,3] deal with its fundamentals, methodology and applications. A flow-injection coulometric method for the determination of chlorpromazine is proposed, in which the quantity of electricity corresponding to the chlorpromazine ion transfer into a plasticized polymeric membrane during the passage of the central portion of the sample plug through the detector cell is measured. Some principles of this technique have previously been presented for the transfer of the model ion tetraethylammonium [17].
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