Abstract
The construction and performance characteristic of a potentiometric PVC membrane sensor for the determination of triphenyltetrazolium chloride (TPTC1) is described. The sensor is based on the use of triphenyttetrazolium (TPT)tetraphenylborate (TPB) ion pair as ion exchange sites in PVC matrix in presence of dioctylphathalte as plasticizer. The TPT membrane sensor shows a stable, nearNernestian response for 6x 10(-6) -1 x 10(-2) M TPTC1 at 25 degrees C over the pH range 3-10 with cationic slope of 57.0 +/- 0.5. The lower detection limit is 4 X0(-6) M and the response time is 10-30 sec. Selectivity coefficients for TPTC1 relative to a number of different cations and anions were investigated, which there is negligible interferences. However, iodide, bromide and thiocyanate were interfering. The determination of 2.0- 3340.0 mu g/ml of TPTC1 in aqueous solutions shows an average recovery of 98.5 % and a mean relative standard deviation of 1.9 at 160 mu g/ml. The proposed method has been used for indirect potentiometric determination of ascorbic acid in its pharmaceutical formulations which are comparable favorably with those of British pharmacopoeia method. Precipitation titrations involving TPTC1 as tit-rant are monitored with NaTPB using the proposed membrane sensor; the inflection break is about 300 mV.