PVC membrane sensor for potentiometric determination of fluoxetine in some pharmaceutical formulations

The construction and general performance of a novel potentiometric membrane sensor for determination of fluoxetine has been developed. It is based on the formation of the ion association complex of fluoxetine with picrolonic acid as electroactive material, dispersed in a PVC matrix and o-nitrophenyl octyl ether as a plasticizer. The sensor shows a fast, stable, and near Nernstian response for 1 x 10(-2) M to 8 x 10(-6) M fluoxetine at 25 degrees C over the pH range of 1-5 with a cationic slope of 51 +/- 0.5 mV/decade. The lower detection limit is 6 x 10-6 M and the response time 20-35 sec. Selectivity coefficients for fluoxetine, related to number of interfering substances, were investigated. There are negligible interferences from the studied cations, anions, and pharmaceutical excipients. The determination of fluoxetine in aqueous solution shows an average recovery of 98.6% and a mean relative standard deviation (RSD) of 1.5% at 100 mu g/mL. The direct determination of fluoxetine in some formulations gave results that compare favorably with those obtained by a spectrophotometric method. The developed membrane electrode has been used as an end point indicator electrode, e.g., potentiometric titration of fluoxetine with sodium tetraphenylborate as a titrant has been monitored.