Read the article to discover the wide-ranging laboratory applications of modern digestion and distillation systems—going far beyond traditional Kjeldahl nitrogen determination (TKN) into diverse analytical fields.
The
Kjeldahl analysis is a highly versatile method, as it can handle an extensive range of samples, from food and feed, beverages, environmental, and agriculture to chemical and pharmaceutical industries. This method provides valuable insights into
nitrogen content, which is crucial for evaluating
soil health,
water quality, the
nutritional value of food products,
quality control,
regulatory compliance, and
process optimization.
One of the main application, is the
Total Kjeldahl Nitrogen (TKN), a measure of ammonia nitrogen and organic nitrogen. Other forms of inorganic nitrogen such as nitrite-nitrogen and nitrate-nitrogen, are not included in this measurement.
This procedure involves a three-step:
- Kjeldahl Digestion: the sample is heated at high temperature after mixing with catalysts and concentrated sulfuric acid;
- Kjeldahl Distillation: the digested sample is treated with a base to shift the equilibrium and obtain free ammonia (NH3); this ammonia is then removed by steam distillation and collected in a proper solution;
- Titration: The distilled ammonia is quantified by titration, allowing for the determination of the total nitrogen content.
Application Beyond Total Kjeldahl Nitrogen
While the
Kjeldahl method remains a cornerstone of
nitrogen determination, the capabilities of modern digestion and distillation systems extend far beyond this singular application. These versatile solutions are integral to a wide array of analytical processes, such as:
- Determination of Ammonia Nitrogen: Ammonia nitrogen is a critical parameter in water quality assessment, as elevated levels can indicate contamination from sources such as wastewater, agricultural runoff, or industrial discharges. Accurate measurement of ammonia nitrogen is essential for monitoring environmental health and ensuring compliance with water quality standards. This method requires that the distillation of ammonia from the sample is followed by spectrophotometric analysis;
- Sulphites Determination: Sulphites, in various forms, have been added to foods as preservatives agents and for other purposes for centuries. Their use became an issue of concern when some sensitive individuals exhibited adverse reactions. This fact lowers the concentration which was considered safe for human consumption and increases the number of control analyses to be performed. One of the most commonly used methods for this analysis is the sulphur dioxide distillation from complex matrixes followed by iodine titration. This method shows comparable results to the ones obtained by using the Monier-Williams technique.
- Nitric Nitrogen (Devarda Method): this method is used to determine nitrate and nitrite nitrogen in a sample by reducing them to ammonia using Devarda’s alloy. When a solution of nitrate ions and Devarda’s alloy is mixed with sodium hydroxide, the mixture gently liberates ammonia gas. The sample is then distilled in a steam flow and collected into an acid solution with indicators, ready for the titration step. The results obtained will be comprehensive of the ammonia nitrogen too, so it has to be subtracted afterwards.
- Phenols: Phenolic chemicals are a growing concern due to their extremely low taste and odor thresholds, high persistence, and toxicity. These compounds can be found both in raw and treated water. While phenols may disperse quickly in the air, they can persist in water for up to a week or more. In soil, phenols can be broken down by bacteria or other microorganisms. The determination of phenols is a routine analysis used to assess water quality, particularly in drinking water, groundwater, and both domestic and industrial wastewater, even at low concentrations. A common method for determining phenols is steam distillation, followed by a colorimetric reaction with 4-aminoantipyrine;
- Total Volatile Basic Nitrogen (TVBN): it is a measure of the total concentration of volatile amines in a sample. These nitrogen compounds are typically formed through the breakdown of proteins during spoilage, especially in seafood. High levels of TVBN are often used as an indicator of spoilage or degradation in fish and seafood products. To perform this analysis, the sample is alkalized by magnesium oxide (MgO), and then, TVBN is determined by steam distillation and titration;
- Alcohol Strength Determination: the alcohol level in wine, beer, and spirits significantly influences their taste, body, and mouthfeel. One common method for determining alcohol content is steam distillation, which separates the ethanol-water mixture from the sample. The alcohol concentration is then measured by determining the density of the distillate using a pycnometer.
Digestion & Distillation Solution for Several Analysis
VELP offers a comprehensive range of digestion and distillation solutions, available with varying levels of automation to suit the specific needs of any laboratory.
Our systems support a wide array of applications, from the determination of Total Kjeldahl Nitrogen (TKN) and protein content, to the analysis of ammoniacal nitrogen, nitrate nitrogen (Devarda method), phenols, TVBN, sulphites, and alcohol content.
Designed for maximum efficiency and precision, VELP units ensure full compliance with international standards such as AOAC, ISO, EPA, and DIN.
Discover more about the UDK Series distillation units by VELP..
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