949 (2002) 281–289 Journal of Chromatography A, www.elsevier.com / locate / chroma Suppressed ion chromatography for monitoring chemical impurities in steam for geothermal power plants a, a b c c * ´ E. Santoyo , S.P. Verma , F. Sandoval , A. Aparicio , R. Garcıa a ´ ´ Centro de Investigacion en Energıa ( UNAM), Apartado Postal 34, Temixco, Mor. 62580, Mexico b ´ ´ ´ Comision Federal de Electricidad, Residencia Geotermica Los Azufres, Michoacan, Mexico c ´ ´ ´ Museo Nacional de Ciencias Naturales ( CSIC), Depto. Volcanologıa, Jose Gutierrez Abascal 2, 28006 Madrid, Spain Abstract A suppressed ion chromatography (IC) technique has been evaluated as a chemical monitoring tool for detecting major 2 2 2 22 anions (F , Cl , NO and SO ) of condensed steam in geothermal power plants. It is shown that the suppressed IC 3 4 technique provides a suitable means for preventing possible damage to generating equipment in the geothermal industry. An electrical conductivity detector (0.1 mS sensitivity) with an anion-exchange column (IonPac AS4A-SC), a micro-membrane suppressor (AMMS II), and an isocratic high-pressure pump system were successfully used for detecting low concentrations of inorganic anions. Method detection limits for the anions of interest were ,0.184 mg / L. Details of the IC methodology as well as some experimental results obtained during its application for the chemical monitoring of geothermal steam pipes are also described.  2002 Elsevier Science B.V. All rights reserved. Keywords: Process control; Geothermal fluids; Inorganic ions 1. Introduction salinity present in the liquid phase [4]. An efficient separation of steam from the mixture is normally The exploitation of geothermal resources for controlled, in situ, by a correct throttling of the liquid generating electricity has shown considerable pro- and steam levels inside the separators. In spite of this gress in Mexico [1]. Two-phase (water–steam) reser- operation, an in-situ chemical analysis of the steam voirs are being commercially exploited in some composition in order to monitor its inorganic ionic Mexican geothermal fields [2]. A working generating impurities is required. This chemical control would fluid with a high steam quality must be efficiently provide a signal if inappropriate operation of the separated from the geothermal fluid (water–steam separators occurs, thus avoiding serious damage to mixture) produced in such natural systems [3,4]. The the generation equipment. Such chemical monitoring presence of liquid in the steam could cause serious should, therefore, constitute an integral part of the problems of scaling and corrosion in the generation operation of power generators in the geothermal equipment (e.g. turbine blades) due to the high industry. To address this special need, in-situ analysis of the inorganic anion composition in geothermal steam *Corresponding author. Tel.: 152-55-5622-9774; fax: 152-55- samples has been suggested as a monitoring ana- 5622-9791. E-mail address: esg@cie.unam.mx (E. Santoyo). lytical tool. From the geochemical point of view, the 0021-9673 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0021-9673(01)01586-2