For water analysis, two common elements of interest to measure are carbon and nitrogen. Both are found in all living things and provide a measure of the level of biological matter in the water sample. Consequently, water quality measurements typically limit the maximum allowable amount in drinking water, wastewater, runoff, etc.

Carbon is more associated with the total contamination level in the water, and measurements of Total Organic Carbon (TOC) are very common in water testing in various applications. Nitrogen’s effects are somewhat more complex. Since proteins are based on nitrogen-bearing amino acids, nitrogen analysis provides a measure of protein content. However, simpler nitrogen compounds, typically based on ammonia, act as fertilizers, and their presence in water can have direct effects on the ecosystem.

For many applications, both elements are of interest, so it is most convenient to measure them simultaneously. Although there are a number of specific techniques for TOC, it turns out that the combustion method can also be used for nitrogen. Consequently, instruments for TOC typically offer the option of a separate module for the detection of the Total Nitrogen (TN) in the sample, also commonly called the Total bound Nitrogen (TN_b).

In combustion analysis, the sample is introduced into a furnace, which typically operates at temperatures of 1200°C or higher. The sample is generally combusted in the presence of a catalyst, which ensures the complete oxidation of the sample. For TOC analysis, the resultant carbon dioxide is detected via non-dispersive IR spectroscopy. For nitrogen, which is converted into nitric oxide, a few different methods can be applied; among them are chemiluminescence, electrochemistry and IR spectroscopy.

Applications are primarily related to water testing in a variety of settings. Water utilities are a major source of demand for nitrogen analysis, as regulations set limits for drinking water as well as for treated wastewater. More generally, environmental testing has many uses for nitrogen testing of surface water and seawater, as well as for monitoring industrial releases. The industrial processes themselves may also require certain limits on contamination in waters used in the process.

The connection with nitrogen as a fertilizer also makes this analysis important for the agriculture and food industries, in order to monitor runoff from agricultural land. Beyond simple water testing, soil can also be analyzed, and this also has importance in both agricultural and environmental testing.

A number of the major TOC vendors also supply TN analysis. While some vendors offer integrated TOC/TN systems, it is more common that the nitrogen module is sold as a separate optional component. On its own, the TN module is priced at about $10,000, but a complete TOC/TN system can run from about $25,000–$50,000.

A few vendors also offer dedicated nitrogen-only combustion analyzers. Shimadzu leads the market, as it does the general TOC market. The next most prominent vendors are Analytik Jena (Endress + Hauser) and OI Analytical (Xylem). Other significant market participants include Elementar, Skalar and Teledyne Tekmar (Teledyne Technologies).

Total Nitrogen at a Glance

Leading Vendors:

• Shimadzu
• Analytik Jena (Endress + Hauser)
• OI Analytical (Xylem)

Largest Markets:

• Utilities
• Environmental
• Agriculture

TN Module Cost:

• $7,000–$15,000