Ion Selective Membrane Electrodes for Determination of Cetrimide in Pure form and in Pharmaceutical Formulations

This paper presents a comparative study between five ion selective electrode sensors which were constructed and validated to determine Cetrimide (CET) by direct potentiometry in pure drug and its mouthwash without sample pre-treatment. Precipitation based technique was used for sensors fabrication. The CET complexes with different types of polyvinylchloride matrix and different cationic exchangers, CET- carboxylated polyvinylchloride (sensor 1), CET- tetrakis (sensor 2), CET- phosphotungestate (sensor 3), CET-tetraphenylborate (sensor 4) and CET- carboxylated polyvinylchloride / tetrakis (sensor 5) were obtained in situ by soaking the PVC membranes in 1×10-4 M CET solution. Nitrophenyl octyl ether (NOPE) was used as plasticizer. Proposed sensors showed fast, stable Nernstian responses across a relatively wide CET concentration range of 7.81×10-6 M to 1×10-3 M (for sensor 1, 2 & 5) and 3.13×10-5 M to 1×10-3 M (for sensor 3 & 4) in the pH range of 1-10 (for sensors 1, 2 & 5) and 5-7 (for sensors 3 & 4). Suggested sensors were found to be stable for several weeks without any measurable change in sensitivity. Validation of the method according to IUPAC recommendations showed suitability and selectivity of the proposed electrodes for the use in quality control assessment of CET in presence of different interferents. Proposed sensors were successfully applied for CET determination in pure form and in its mouthwash where good responses were obtained regarding accuracy and precision.