Metrolab Blog

Low Nitrogen Liquid samples | Obtain accurate results with the New Mineralization Rod for Kjeldahl digesters

For low nitrogen content samples, such as water and beverages, the Kjeldahl analysis requires a high sample volume.
Due to the sample quantity, foam formation and violent bumping may develop during the digestion, causing acid splash on the test tube wall. Sample loss may occur therefore, leading to inaccurate results, underestimating the nitrogen content.
The use of the mineralization rod helps avoid this issue.

Kjeldahl Digestion Phase: efficiency and accuracy
The digestion phase is the most time-consuming step of the Kjeldahl analysis. Speeding up the process ensuring a proper outcome is of fundamental importance when it comes to the accuracy of the results and efficiency in the lab.
In the digestion phase of the Kjeldahl analysis, the goal is to break down the bonds that hold the polypeptides together and convert them into simpler molecules (such as water, carbon dioxide and ammonium sulfate). These reactions can be speeded up by the temperature used during digestion and by the presence of acid, salt and catalysts (selenium, copper, mercury, titanium).
After having weighed the sample, the latter must be placed into a glass test tube along with concentrated sulfuric acid and the correct variety of catalyst tablets according to the Official Methods requirements. As a matter of fact, catalyst tablets containing copper are satisfactory but very slow to react, while selenium catalysts usually react very fast and are typically used for substances that are resistant to digestion (e.g. fats and oils).
For low nitrogen content samples, such as water and beverages, the analysis requires a high sample volume. Therefore, foam formation and violent bumping may occur during the digestion, causing acid splash on the test tube wall. This can lead to sample loss and, ultimately, to inaccurate results that underestimate the nitrogen content.

VELP Mineralization Rod optimizes the Kjeldahl analysis on low nitrogen liquid samples
The VELP new mineralization rod optimizes Kjeldahl analysis for Nitrogen determination in liquid samples with low nitrogen content and is especially suggested for the following applications:

  • TKN determination in water and wastewater
  • Nitrogen/Protein determination in beer
  • Nitrogen/Protein determination in beverages

The use of the mineralization rod helps avoid possible issues related to foam formation and violent bumping during the digestion of the liquid sample.
The mineralization rod has to be simply added to the test tube with the sample and chemicals before starting the digestion process. Then it remains in the test tube until the end of the whole Kjeldahl analysis, distillation step included.
The main advantages using this accessory are:

  • Foam reduction
  • Violent bump and acid splashes minimization
  • Better heat distribution in the whole sample
  • Digestion time reduction up to 75%
  • Sample, reagents, and energy saving
  • Possibility to use the “Empty test tube” function on the UDK Distillation Units (not possible with boiling stones/chips)