Composites:: A novel alternative to construct solid state Ag/AgCl reference electrodes

An Ag/AgCl solid-state reference electrode is developed by means of a graphite-AaCl-Silver dag-epoxy resin composite. The response of the composite reference electrode (CRE) to chloride ions is evaluated; a linear non-nernstian response is observed associated to the following equation E = -15.15 (+/- 1.10) -44.05 (+/- 0.38) log[Cl-]. Comparing the CRE's response potential versus a saturated commercial Ag/AgCl reference in KCl 0.1 M, a mean of 40.7 +/- 0.4 mV of the distribution of potential versus time data is observed over a period of I h. The performance of the CRE as reference for a glass membrane electrode by means of direct pH measurements and quantitative determination of acids by acid-base titrations is evaluated obtaining statistically stable, precise and exact results compared with those obtained using a combined glass electrode. The typical cylindrical configuration of the CRE is changed to adapt it to a FIA system for the determination of ammonium ion, obtaining a sensitivity 50.30 +/- 0.26 mV/log[NH4+] and a linear range 8.5 x 10(-5) to 0.1 M, which are analytical parameters statistically equivalent to those presented by the classical determination system. (C) 2005 Elsevier B.V. All rights reserved.