Determination of anions in thermal waters of coffee region of Colombia using ion chromatography

Recently, there has been an increasing demand for hydrogeological characterization of thermal anomalies around the world, in Colombia there are about 121 thermal waters, but there is limited chemical information on Colombian hot springs. Here we have established an ion chromatography method for the determination of anions in thermal waters. Using the Dionex® IonPac® AS20 column, gradient mobile phase of potassium hydroxide (KOH), and suppressed conductivity detection a favorable chromatographic separation of seven anions was achieved in 15 min with satisfactory resolution. The limit of detection (LOD) and limit of quantitation (LOQ) of this method were less than 2.95 mg L −1 and 6.96 mg L −1 , respectively, and the intra- and inter-day relative standard deviation (RSDs) were between 0.21-1.08% and 0.63-4.43%, respectively. The method showed good repeatability and linearity, making it suitable for the determination of anions in water samples. Under optimal conditions, the established method was used to quantify anions in six thermal water samples. The results showed that chloride and sulphate were the predominant anions in all the thermal waters studied. Our experiment demonstrate that different geological and geochemical factors influenced the chemistry characteristic of the thermal waters; in fact, the proximity to the volcanoes present in the study area was considered a reason for the variation in anions, with sulphate being the most differential anion.