Total Protein – Dumas Method vs Kjeldhal

Exploring the Dumas Method: Total Protein Analysis in Food and Feed

Understanding the Dumas Method for Total Nitrogen and Protein Analysis

The Dumas method, often referred to as the combustion method, is a modern approach to determining total nitrogen content, which can be further used to estimate protein content in food and feed samples. Developed as an alternative to the older Kjeldahl method, the Dumas method has been gaining popularity due to its speed, efficiency, and environmental friendliness. This article will explore the Dumas method, compare it with the Kjeldahl method, and highlight its advantages.

What is the Dumas Method?

The Dumas method is named after Jean-Baptiste Dumas, a 19th-century French chemist who devised the technique. It involves burning a dried sample in an oxygen-rich environment at high temperatures (about 900°C to 1000°C). During combustion, the nitrogen present in the sample is converted into nitrogen oxides and then reduced to nitrogen gas. The nitrogen gas is subsequently measured using a thermal conductivity detector or other types of detectors depending on the system configuration, such as those in the systems provided by Skalar NL.

 Steps in the Dumas Method:
1. Sample Preparation: The sample is dried and ground to ensure it is homogenous.
2. Combustion: The sample is combusted in a pure oxygen environment at high temperatures.
3. Reduction: The gases produced are passed over a copper catalyst to reduce nitrogen oxides to elemental nitrogen.
4. Detection: The nitrogen content is quantified, usually thermal conductivity detectors.

Kjeldhal Method for total N/ Total Protein

 A Comprehensive Review of the Kjeldahl Method for Nitrogen and Protein Analysis

The Kjeldahl method remains a staple in analytical chemistry for quantifying the total nitrogen content in diverse samples, such as food, feed, and agricultural products. Developed in 1883 by Danish chemist Johan Kjeldahl, this classical technique has been recognized for its precise and reliable protein estimations. This article provides an in-depth exploration of the Kjeldahl method, detailing its procedural steps and examining its key features and applications.

The Kjeldahl method has been the traditional approach for nitrogen and protein analysis. It involves three main steps: digestion, neutralization, and distillation. 

 Detailed Process of the Kjeldahl Method

  1. Digestion

   – The Kjeldahl method begins with the digestion of the sample in concentrated sulfuric acid at temperatures between 360–410°C. This process oxidizes the organic material, releasing nitrogen as ammonium sulfate. The reaction is enhanced by catalysts such as selenium, mercury sulfate, or copper sulfate, and substances like sodium sulfate or potassium sulfate are added to raise the boiling point of the mixture.

  1. Neutralization

   – Following digestion, the acidic mixture is neutralized with sodium hydroxide, setting the stage for distillation by adjusting the pH to a basic level.

  1. Distillation

   – During distillation, ammonia is liberated from the addition of excess base and is captured in a solution of boric acid or another acid. This is a pivotal step where the converted nitrogen (as ammonia) is quantitatively gathered for analysis. The end of the condenser is submerged in a known volume of standard acid, and the sample solution is distilled with a small amount of sodium hydroxide to drive off the ammonia, which then reacts in the acid solution to form ammonium salts.

  1. Titration

   – The process culminates in titration, where the ammonia collected is titrated with a standard acid solution, such as hydrochloric or sulfuric acid. This step determines the amount of nitrogen in the original sample by measuring the ammonium ion concentration in the acid solution. Depending on the acids used, direct acid-base titration or indirect back titration is employed to quantify the nitrogen content accurately.

 Characteristics and Considerations of the Kjeldahl Method

Accuracy: Known for its precision, the Kjeldahl method is often the benchmark for nitrogen determination in protein analysis.

Versatility: It can be applied to a broad range of sample types, making it essential in numerous lab settings.

Labor Intensity: The method demands extensive hands-on involvement, requiring meticulous attention from digestion to titration.

Safety and Environmental Concerns: The use of potent acids and bases mandates rigorous safety measures and careful management to mitigate hazards and environmental impacts.

 Applications and Significance

The Kjeldahl method is foundational in fields like agriculture, environmental science, and food quality control, where accurate protein analysis is critical. Despite newer methods such as the Dumas method, the Kjeldahl method's reliability and precision keep it relevant in many professional settings.


While the Kjeldahl method is renowned for its accuracy, its process is time-consuming and requires the use of strong acids and bases, which pose safety risks and environmental concerns.

Its laborious nature and the need for hazardous chemicals are significant drawbacks. As scientific and industrial landscapes evolve, there is a growing inclination to supplement or replace it with quicker, safer methods like the Dumas method, which offers greater efficiency and reduced environmental impact for broader applications.

Dumas vs. Kjeldahl Method: A Comparative Overview

TComparison of Key Features:

Speed: The Dumas method can analyze a sample in a few minutes, whereas the Kjeldahl method may take tens minutes and involved in longer labor time.
Safety: Dumas does not require hazardous chemicals like sulfuric acid used in Kjeldahl, presenting a safer working environment.
– Precision and Accuracy: Both methods offer high precision and accuracy; however, the Dumas method provides a faster feedback loop for quality control.
– Environmental Impact: The Dumas method is more environmentally friendly, with no hazardous waste requiring disposal compared to the chemical waste from the Kjeldahl method.
Ease of Use: Modern Dumas analyzers, such as those from Skalar NL, are typically easier to operate with automated features and require less hands-on time from technicians.

Advantages of the Dumas Method vs Kjeldhal Method

Efficiency: Rapid analysis allows for higher throughput in laboratories.
Automation: High degree of automation reduces potential for human error and frees up technician time for other tasks.
Lower Operational Costs: Fewer reagents and no need for acid disposal reduce the operational costs significantly.
Scalability: Systems like those from Skalar NL can easily handle a large number of samples, making them ideal for both small and large laboratories.


The Dumas method offers a modern, efficient, and safer alternative for determining total nitrogen and by extension, protein content in food and feed samples. Its advantages over the Kjeldahl method make it particularly suitable for laboratories looking to improve throughput and reduce environmental impact. As the industry continues to evolve, adopting innovative technologies like the Dumas analyzers  will be key to staying competitive and ensuring the highest standards of quality and safety in food and feed analysis.

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The PrimacsSN-100 presents an ideal solution for laboratories requiring swift and precise analysis of proteins across a diverse range of food and feed samples. Utilizing automation, this system significantly reduces analysis durations and amplifies sample throughput.

Ensuring utmost accuracy, our analyzers undergo rigorous testing and calibration to align with each customer's standards, guaranteeing optimal and precise results.

Key attributes of the PrimacsSN-100 include a 100-position random access autosampler with the option to prioritize samples, reusable ceramic crucibles, and capacity for sample weights up to 3g of solid material and 1g of liquid material. Its vertical sample introduction system facilitates seamless insertion of samples into the high-temperature combustion furnace, preserving sample ashes within the crucible to prevent buildup in the combustion zone and minimize maintenance time.

The determination of Total Nitrogen (TN) and protein content relies on the Dumas method and Thermal Conductivity detection (TCD), offering a rapid, safe, and eco-friendly alternative to traditional Kjeldahl methods. Pre-loaded methods cater to various sample types, including cereals, dairy, starch, grains, meats, animal feed, malt, and more.

A unique temperature ramping program is integral to the PrimacsSN-100, particularly beneficial for samples prone to erratic combustion behaviors like meat and vegetable oil. This patented technique allows for customized combustion temperature profiles tailored to specific sample matrices, ensuring optimal combustion patterns for accurate analysis.

Overall, the PrimacsSN-100 delivers fast, precise, and reliable TN/protein analysis across a spectrum of food samples, facilitating uninterrupted operation for enhanced efficiency and high-quality results.

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