TIPS FOR CHOOSING BETWEEN DUMAS AND KJELDAHL METHOD FOR N/PROTEIN DETERMINATION

26/08/2022

Kjeldahl and Dumas are two official methods for Nitrogen and protein determination. Read the news to find out their main features and learn how to choose the one best suited to your needs.

TIPS FOR CHOOSING BETWEEN DUMAS AND KJELDAHL METHOD FOR N/PROTEIN DETERMINATION

The Dumas analytical method (also known as Combustion Method) is becoming more present in many laboratories as the most suitable for N/protein determination compared to the traditional Kjeldahl analysis.

In the past, it was not easy to reproduce the conditions required by the Dumas method. For this reason, the Kjeldahl method took the lead and became the most popular method for Nitrogen/protein determination, and today many laboratories are still focusing on the Kjeldahl system only.

It's worth remarking that both are primary methods working in accordance with international standards (AOAC, AACC, ASBC, ISO, IFFO, OIV)

Let's discover the advantages of the Dumas method and how to choose the proper technique based on your laboratory needs.

Key points of Dumas combustion analysis

The Dumas nitrogen determination requires well-homogenized samples, heated in a high-temperature furnace where the combustion occurs rapidly at over 1000 °C in the presence of pure oxygen.

This produces mostly water, carbon dioxide, and nitrogen as several oxides (NyOx). This gas mixture passes through a reduction chamber containing Vcopper heated to around 650 °C.
This stage converts nitrogen oxides into elemental nitrogen and collects the excess oxygen.

Different traps remove the residual water and carbon dioxide, and a thermal conductivity detector measures total nitrogen content.

The Dumas main advantages are:

Fast and convenient: batch analysis of up to 117 samples
Safe since it does not require the use of harmful chemicals, toxic and catalysts
Accurate and precise: very low LOD
Reduced Footprint: it requires a small bench space in the lab, with only one compact unit

Results obtained with the Dumas nitrogen determination are usually a little bit higher than with Kjeldahl since even the heterocyclic compounds and nitrogen compounds (e.g. nitrites and nitrates) are detected.

In the Kjeldahl method, such compounds are converted into the ammonium ion incompletely or not at all. The opposite could also happen (rarely) because in this kind of analysis there are lots of variables that could influence the final result.

Factors to consider to choose the most appropriate method according to your needs

To choose the correct method for your needs, you should consider:

1. LAB PRODUCTIVITY
When the laboratory occasionally performs a small number of analyses, the Kjeldahl method is the most practical choice. Since the Dumas equipment takes time to start up, it is suitable for continuous use. The Kjeldahl method, on the other hand, can be used at any time for on-the-spot analysis.

2. TYPE OF SAMPLE
The Kjeldahl method enables a larger sample size, which is important in particular lab applications.

3. TURNAROUND TIME
The Dumas method is the best choice when time is crucial since it requires 3/5 minutes for each sample analysis. A standard Kjeldahl analysis it usually takes longer considering the Digestion, Distillation, and Titration steps.

Learn more about official methods for N/Protein determination

For the determination of N/Protein content, the Dumas combustion method is a valid alternative to the Kjeldahl analysis, as it offers shorter analysis times, ease of operation, and improved safety.

Interested in figuring out which method best suits your needs?

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