Monitoring common cations and ammonium is not as prevalent as common anions, but is as important. Cation and ammonium levels are only regulated by some environmental agencies around the world. The EU and Japan require monitoring of cations and ammonium, but the US does not consider these primary water contaminants. Regardless of regulatory requirements, measuring cations and ammonium is very important and is done by public water suppliers and effluent discharge sites because of the valuable information this monitoring provides.
Some cations are indicators of water quality while others can have adverse effects on the environment. For example, calcium and magnesium are indicators of water hardness. Water hardness can not only help determine drinking water quality; it is also important to measure for corrosion control in industrial processes. Sodium is very important to monitor due to the impact on human health and those who are on sodium-restricted diets. Sodium can also be an indicator for the sources of other ions present in water. Many communities will measure sodium to detect road salt contamination in drinking water sources, especially in wells. Road salt contamination can be suspected when higher than expected chloride amounts are detected during anion analysis.
Like sodium, potassium can be an indicator of origin of other ions contaminating water. Most often, elevated levels of potassium can indicate runoff from fertilizers, especially if high amounts of nitrate, nitrite or phosphate are found during anion measurements.
Ammonium is one of the most important cations to monitor, especially at effluent sites, because high amounts can be toxic to aquatic life. Dissolved ammonia gas in water will be generated from anaerobic decomposition of nitrogen containing compounds from waste streams. Ammonia exists in equilibrium with the ammonium ion in water. The amount of dissociation, therefore, presence of the ammonium ion is dependent on water pH and temperature. Monitoring ammonium is extremely important at wastewater discharge sites but will also be measured in drinking water. For more information on the background of cation, monitoring see Thermo Fisher Scientific™ Dionex™ Application Update 204.
The most common analytical technique for monitoring cations and ammonium is ion chromatography (IC). Using IC is very advantageous for this application because all of the ions of interest can be separated and quantified for each sample in one analysis. IC is also a very sensitive technique which can obtain levels down to the low ppm or mid-ppb amounts, using the standard conductivity detection method. While other techniques, such as colorimetric methods, can be used to accomplish these measurements, they often require separate methods for each ion or analyte. These methods and can be complex and labor-intensive when multiple analytes in one sample need to be analyzed.
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The new Thermo Scientific™ Dionex™ Easion™ Ion Chromatography System makes cation and ammonium analysis very simple. Only two solutions need to be prepared by dilutions from concentrates and the system equilibrated to be ready to analyze environmental, drinking and wastewater samples.
The Dionex Easion system also makes cation counterion suppression extremely easy and straightforward. Counterion suppression is just as important for cation applications as it is for anions. Without counterion suppression, the sensitivity of your cation methods will be greatly reduced, losing one of the major benefits for doing ion chromatography.
Setting up the Dionex Easion system for counterions is very simple and easy. The eluent and regenerant solutions are prepared and the cation columns, such as the Dionex™ IonPac™ CS12A or Dionex™ IonPac™ CS16 are attached to the system. The Dionex CCRS 500 is put in place and the regenerant solution is connected to the suppressor and the eluent from the conductivity detector is connected to the regenerant bottle. The system pump is then started, and the system is equilibrated to get the Easion IC ready for analysis. This makes cation counter suppression very easy and cost-effective since no other items, like pumps and complex tubing setups are needed.
To celebrate simplicity in ion chromatography for cation and ammonium analysis and learn about Thermo Scientific™ Dionex™ Easion™ Ion Chromatography System, download our application note: Low-cost determination of inorganic cations and ammonium in environmental waters