New Schiff base modified carbon paste and coated wire PVC membrane electrode for silver ion

A new modified carbon paste electrode (CPE) and a coated wire PVC membrane electrode (CWE) based on a recently synthesized Schiff base of [bis 5-(4-nitrophenyl azo)salisylaldimine] 1,8-diamino, 3,6-dioxo octan (BNSAO) as a suitable carrier for Ag+ ion are described. The electrodes exhibit a Nernstian slope of 56.2 +/- 0.7 (CWE) and 58.4 +/- 0.3 (CPE) mV per decade for Ag+ ion over a wide concentration range from 3.1 x 10(-2) to 9.0 x 10(-7) M for CPE and 2.7 x 10(-2) to 1.9 x 10(-6) M Ag+ for CWE. The lower detection limits are 4.2 x 10(-7) M Ag+ for CPE and 7.8 x 10(-7) M Ag+ for CWE electrode. Their electrodes have a fast response time (similar to 5 s), a satisfactory reproducibility and relatively long life time. The proposed sensors show a fairly good selectivity toward Ag+ ion in comparison to other common cations. The potentiometric responses are independent of the pH of the test solution in the pH range 3.5-7.0 for CPE and 2.5-7.0 for CWE. The proposed electrodes were used as indicator electrodes in potentiometric titration of silver ion with standard solution of potassium iodide. The direct determination of silver in spiked wastewater and radiology film gave results that compare favorably with those obtained by the atomic absorption spectrometric method. (c) 2005 Elsevier B.V. All rights reserved.