Abstract
The construction and general performance characteristics of two novel potentiometric membrane sensors responsive to bismuth are described. The sensors are based on the use of ion-association complexes of tetraiodobismate(III) (TIB) anion with polyoxyethylene(10) octyl phenyl ether (1) and tris(1,10-phenanthroline)iron(II) (2) as exchange sites in a carbon paste matrix. The sensors show fast, stable, and near-Nernstian response for the mono-charged anion of tetraiodobismate(III) over the concentration range 1 x 10(-3)-1 x 10(-6) mol dm(-3) at 25 degrees C over the pH range 4.0-9.0 and 3.0-8.0 with an anionic slope of 51.5 +/- 0.5 and 53.0 +/- 0.4 per concentration decade for tetraiodobismate(III)-1 and -2 (sensor-1 and sensor-2), respectively. The lower detection limit was 4 x 10(-6) and 2 x 10(-6) mol dm(-3) with a response time of 20-40 s for sensor-1 and sensor-2 in the same order. The selectivity coefficients for bismuth relative to a number of interfering anions and iodide complexes of some metal ions were investigated. Direct potentiometric determination of 1-200 mu g cm(-3) of bismuth in aqueous solution showed an average recovery of 98.4% and a mean relative standard deviation of 1.5% at 80.0 mu g cm(-3). The determination of bismuth(III) in suppositories and ointment dosage form in the present study was comparable with the British pharmacopoeia method.