Miniaturized Membrane Sensors for the Determination of Orphenadrine Citrate

Novel miniaturized polyvinyl chloride (PVC) membrane sensors in all-solid state graphite and platinum wire supports were developed, electrochemically evaluated and used for the assay of orphenadrine citrate (ORP). The ORP sensors were based on the formation of an ion-association complex between the drug cation and tetrakis(4chlorophenyl)borate (TpClPB) anionic exchanger as electroactive material dispersed in a PVC matrix. Linear responses of 10 -2 - 10 -5 M and 10 -2 -10 -4 M with cationic slopes of 56.4 mV and 53.6 mV over the pH range 4-7 were obtained by using the ORP-coated graphite (sensor 1) and platinum wire (sensor 2) membrane sensors, respectively. The proposed methods displayed useful analytical characteristics for the determination of ORP in Norflex ® tablets with average recoveries of 100.01±0.83, 100.09±0.90, and in plasma with average recoveries of 99.4±0.97 and 98.55±0.82, for sensor 1 and 2, respectively. The methods were also used to determine the intact drug in the presence of its degradate and thus could be used as stability indicating methods. The results obtained by the proposed procedures were statistically analyzed and compared with those obtained by using an official method. No significant difference for both accuracy and precision was observed.