Abstract A simple computerized potentiometric titrator is described for performing automated analyses of chloride ions on solid materials as well as the continuous determi- nation of HCl in effluent gas streams. This versatility has been obtained by a dedicated instrumental design, which offers easy interfacing to catalytic reactors and flexibility in software programs, including Gran’s plot determination of end-points. The validation of the analytical methodol- ogy for quantitative determination of chloride ions in solid matrices required the definition and the preparation of suit- able reference materials of known chloride content. 1 Introduction Chloride ions are ubiquitous impurities in material science, particularly in heterogeneous catalysis [1, 2], where they are well-known to play a dual role. They can promote both activity and selectivity, e.g. in Pt/Al 2 O 3 catalysts for pe- troleum reforming [3], or they may act as poisons by irre- versible adsorption on the active surface [4]. Moreover, an- hydrous transition metal chlorides are often volatile, there- fore the presence of chloride ions may promote metal leach- ing during the process of oxidative redispersion of metal catalysts [5]. This leaching of noble metals may have a significant relevance in environmental science, since they are present as major active components in automotive cat- alytic converters. The development of simple, automated methods for chloride ion analysis in catalytic science has recently re- ceived an additional stimulus by the need of finding stable and active catalytic materials for the reutilization and/or abatement of ozone-depleting chloro-fluoro-carbons (CFC) via hydrodechlorination reactions [6]. Many different ap- proaches have been proposed to chloride ion analysis in solid catalysts and in effluent gases, ranging from XPS [7] to conductometric analysis [8]; however, no simple and flexible approach to the determination of chlorides in both solid catalysts and in effluent gas streams has yet been re- ported. In order to solve this problem, we have evaluated poten- tiometry as the most suitable analytical methodology, since titrimetric methods offer the advantage of high immunity to interferences and the continuous monitoring of chloride concentration may be easily obtained. Moreover, high sen- sitivities are rarely required and instrumentation is now well established. Many instrumental approaches, some of them are now commercial, have been published on auto- mated potentiometric titrators [9, 10]. However, commer- cial instruments are generally unlikely to be easily and di- rectly interfaced to existing catalytic reactors and do not often allow both titrations and time-dependent ion analy- sis to be performed simultaneously on the same instrument. In this paper, we will describe a simple and dedicated potentiometric titrator for automated chloride analyses in catalytic science. Specific software programs were devel- oped, in order to control all pieces of hardware via RS232 serial interfaces. The analytical system is designed to carry out the continuous determination of HCl in gaseous efflu- ents as a function of reaction time together with the titri- metric determination of chloride contents in solid materials. This combined approach can also allow the determination of the mass balance of chlorine during catalytic reaction. 2 Experimental Instrumental system for automated potentiometric titration of chloride ions A microprocessor-based pH/mVmeter (AMEL 338 by AMEL srl, Milan (Italy)) and a digital burette (CAT LiquidProcessor, by Carlo Dossi · Sandro Recchia · Achille Fusi Automated chloride analysis in catalytic science: a low-cost hardware and software implementation Fresenius J Anal Chem (2000) 367 : 416–421 © Springer-Verlag 2000 Received: 8 November 1999 / Revised: 21 January 2000 / Accepted: 29 January 2000 ORIGINAL PAPER C. Dossi () · S. Recchia Dipartimento di Scienze Chimiche, Fisiche e Matematiche, Università dell’Insubria, Via Lucini 3, 22100 Como, Italy and Centro CNR “CSSSCMTBSO”, Via Venezian 21, 20133 Milano, Italy e-mail: dossic@fis.unico.it A. Fusi Dipartimento di Chimica Inorganica, Metallorganica e Analitica, Università di Milano and Centro CNR “CSSSCMTBSO”, Via Venezian 21, 20133 Milano, Italy