Determination of chloride, sulfate and nitrate in groundwater samples by ion chromatography

Groundwater is a significant source of water for both domestic and agricult ural use in some regions of the Maracaibo lake basin in Venezuela. Chemical ly suppressed ion chromatography with a Dionex Model 2000i/sp, Ionpac AS11, ASRS-I system was used for the analysis of major inorganic anions in groun dwater samples. About 50 samples of groundwater, taken over several months in three different locations, were analyzed after filtration and sometimes dilution. In all the samples, the separation between the peaks of chloride, nitrate and sulfate showed good resolution (symmetrical peaks, not broaden ed), even when the chloride concentration was as high as 850 mg l(-1) and r eproducibility (RSD) was similar to 2%. No other peaks (i.e. fluoride, nitr ite and phosphate) were observed at selected experimental conditions. With the chosen parameters, the method is well-suited for the routine determinat ion of these anions in groundwater samples, giving results in less than 10 min (induding column clean-up). With an appropriate combination of detector output ranges (300 and 1000 mu S), only one set of calibration solutions w as needed for all samples. In the Sierra Maestra location, the groundwater samples, were significantly different in total anion levels. Mean total chl oride plus sulfate concentrations (similar to 525 mg l(-1)) were about 100 times higher than in the other sites. Some water quality implications of th ese groundwater samples are also discussed. (C) 2000 Elsevier Science B.V. All rights reserved.