Water for Kjeldahl Analysis
Impact of Water
Water is used in many steps of the Kjeldahl analysis. It is used in the preparation and dilution of the reagents, standards and samples, and for rinsing the glassware and the apparatus. Water may also be used after the digestion step, and to generate steam for the distillation step of the analysis. It may also be used for cooling (in condensers, etc.).
The following water contaminants may interfere with the analysis and should be avoided:
- Ammonia and nitrogen-containing molecules
Molecules containing nitrogen (organic and inorganic) may interfere with the analysis, and lead to erroneously high results. For instance, nitrates, can disturb the nitrogen mass balances. All nitrogen-containing compounds should be kept to a minimum.
- Ions and metals
Calcium and magnesium salts, as well as metals (iron, copper and manganese) may generate deposits when the water is heated to produce steam. These deposits may restrict water flow and reduce the heat exchange efficacy of the steam generator. More frequent maintenance will also be needed.
- Particles
Particles may form deposits in the vessels or when steam is generated. Removing these deposits may be cumbersome.
- Bacteria
Bacteria levels should be kept to a minimum, as they may form biofilms in the steam generator, and lead to additional need or maintenance. In addition, bacteria release by-products, including nitrate, nitrite and other nitrogen-containing compounds, that may interfere with the analysis.
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