Dumatherm is a highly efficient, precise and fast alternative to Kjeldahl for the determination of Nitrogen. For most sample matrices, it is a real alternative to other classical procedures. In the Dumas method, a sample is burned in an oxygen rich atmosphere at high temperature and the resulting gases analysed. The direct analysis of all resulting gases provides the user with results within 2-3 minutes. Dumatherm very few parts subject to wear and tear, which reduces costs for service significantly. Operation and control of the apparatus is done entirely via PC using the Dumatherm Manager.
During each measurement the total amount of nitrogen is analysed with a detection limit of 0.01 mg N absolute. The maximum detectable amount of nitrogen is 50 mg nitrogen from sample weights up to 1g. The Dumatherm system can be supplied with manual sample entry or a 40-position auto-sampler, which can be easily expanded to 80 or 120 positions. Loading of the auto-sampler is also possible during analysis. The manual sample entry system can be easily upgraded to an auto-sampler in the future.
Dumatherm is entirely controlled and operated using the controlling software Dumatherm Manager. This software is capable of handling all parameters of the instrument and analysis, documentation function and system diagnosis.
Data Interpretation
All analysis data is stored in a coarse data base (history) and can be copied from this table into Excel data files for interpretation. For a series of samples or a single sample, a detailed print out of the analysis parameter and the results, including an error calculation can be obtained.
Method
Samples between 50 and 40mg are weighed into tin foils and placed on the auto-sampler carousel. Samples are dropped into the pure camber were all oxygen is removed. The sample is then dropped into the furnace at around 1000°C. Oxygen is injected into the furnace to burn the sample and oxidise the Nitrogen.
Within the reaction chamber the ash is removed and catalytic beds ensure complete combustion of the sample. Controlling the gas flow carefully reduces sooting within the unit and reduces maintenance and downtime. In the next stage the Nitrogen is reduced back to elemental Nitrogen by using a copper reduction catalyst. Oxygen, water, and Carbon dioxide are all removed before the Nitrogen passes over the detector.
Passing the gas over a Thermal Conductivity Detector completes the volumetric determination of the nitrogen content. From the amount of Nitrogen detected in the sample and knowing the weight of the sample introduced into the system the percentage protein can be determined.
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