Cation Analysis

Ammonia gas produced from agriculture and wastewater treatment plants poses a severe threat to aquatic life by breaking the balance of sensitive habitats. When dissolved in water, ammonia exists in an equilibrium between its molecular form associated with water and ammonium cation. The extent of its toxicity to aquatic life depends upon the extent of dissociation. Monitoring of ammonium cations provides information on the amount of ammonia dissolved in water, and is required for the National Pollutant Discharge Elimination Program (NPDES) permit during the wastewater treatment process. Ammonium ion is also monitored in the EU and Japan in both wastewater and drinking water.

In addition, small polar amines are often used as additives in power plant waters, such as ethanolamines. Several disparate small polar amines are often analyzed in industrial wastewaters.

On this page, you will find:

• Cation analysis techniques
• Cations analysis in drinking water, environmental waters, and municipal wastewaters
• Cations analysis in industrial wastewaters

Ion chromatography (IC), specifically cation chromatography, is another technique that is often used to separate and quantify alkalai and alkaline earth metals, as well as ammonium cation in a single analytical run in less than 30 min at ppt or lower detection limits.

For the past 20 years ion chromatography with suppressed conductivity detection has proven to be a robust and reliable technique for the determination of cations. The advantages that cation suppression provides justify the investment. In fact, the use of suppressor systems is mandatory for employing high-capacity columns or gradient elution techniques. The higher capacity improves performance for trace level determinations of cations in high ionic strength matrices by extending the linear range and resolving higher concentration ratios of sodium and ammonium cations. The problems associated with cation suppression identified in the past―low sensitivity and nonlinear calibration for weakly dissociated cations―are no longer an issue.

By ion chromatography: Due to its toxicity, ammonium is a required target analyte monitored in municipal wastewater effluent as part of the NPDES wastewater discharge permit requirements. Additionally, as wastewater samples have high concentrations of sodium, it is often important to separate relatively low concentrations of ammonium in the presence of excess sodium.

By discrete analyzer: As described above, a discrete analyzer is often used for analysis of ammonium in drinking water, environmental water, and wastewater, as demonstrated in ISO 15923-1. The instruments described in below application notes are easy to use and need no additional priming or method changeover time thereby giving fast analyzing results.

In power plants, the buildup of impurities at sub-ppb levels of metal contaminants can result in their accumulation in steam generators or turbines. Therefore, monitoring the presence of ionic impurities in cooling waters, boiler waters, feed waters, and steam condensate in both fossil-fueled and nuclear power plants is of critical importance.

• These impurities can propagate stress corrosion cracking and other corrosion mechanisms in turbines, steam generator tubing, and other plant components.
• This corrosion can eventually lead to component failures and plant shutdowns, resulting in millions of dollars of lost revenue.
• Corrosive ions, such as sodium, chloride, and sulfate, can be minimized by continuously monitoring their respective levels and maintaining these levels as low as possible by taking the appropriate action.

Morpholine was used as an additive in power plant waters because it was less volatile than the commonly used ammonia under all volatile treatment (AVT).

• However, ammonia was still present from the thermal decomposition of morpholine.
• Less volatile amines with higher base strengths, such as ethanolamine, eventually replace morpholine
• Large concentrations of one or more amines can make the determination of trace concentrations of other amines and cations difficult

Analysis of alkanolamines is also important in metal surface finishing and in wastewater effluents. alkanolamines are commonly used in acid gas removal systems (scrubbers) in both oil refineries and natural gas plants.

• Hydrogen sulfide and carbon dioxide form weak acids when the gases are dissolved in an aqueous medium
• Amines, weak bases, react with the weak acids to form salts and thereby removing the acid gases from the process stream
• When the amine solution is overloaded with salts, the scrubbing process is adversely affected

Thus, continuous monitoring of the amine solution can improve amine makeup, improve final product performance, and decrease system maintenance.

See all Learning Centers ›