New in situ modified PVC membrane electrodes for potentiometric determination of gentamicin sulfate in its pharmaceutical formulation and biological fluids

The construction and performance characteristics of five new, simple, rapid, selective and sensitive in situ modified poly vinyl chloride (IPVC) membrane electrodes are described for determination of gentamicin sulfate (GNS) in raw material, pharmaceutical formulations and biological fluids (plasma and urine) using dibutylphthalate (DBP) as plasticizer. Sensor 1(S1) was fabricated using cation exchanger sodium tetraphenylborate (NaTPB), sensor 2 (S2) used phosphotungstic acid (PTA), sensor 3 (S3) used Phosphomolybdic acid (PMA), sensor 4 (S4) used ammonium reineckate (RN) and sensor 5 (S5) used a mixture of RN + NaTPB. The electrodes under investigation exhibit suitable response to GNS in the concentration range from 1 x10-6 to 1 x10-2 M for S1, S2, S3 and S5 and from 1 x10-5 to 1 x10-2 M for S4. The electrodes have values of 30.5±0.8, 28.7±0.6, 29.9±0.7, 25.8±0.5 and 31.0±0.9 mV decade-1 with detection limit values of 8.9 x 10-7, 9.4 x 10-7, 9.1 x10-7, 9.7 x 10-6 and 8.5 x 10-7 M GNS using S1, S2, S3, S4 and S5, respectively. The electrode response is independent of pH in the range of 3-9 for S1, S2, S3 and S5 and in the range of 3-7 for S4. All electrodes shows fast response time which is very short (? 12 s), and were used over a period of 60 days with good reproducibility. The selectivity coefficients indicated good selectivity for GNS drug over a large number of interfering materials (inorganic cations, amino acids and sugars). The proposed electrodes were successfully applied to the determination of GNS in raw material, pharmaceutical formulations and biological fluids. The results were validated by comparison with the official method.