Dumas Application A.2.2.1 Nitrogen in Feedstuff

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A. 2.2.1 Dumas Nitrogen in Feedstuff

Application_A.2.2.1. Nitrogen in Feed Dumas_08.2020_english.doc • Rev.: A • Page 2 of 6

1 Principle The nitrogen contained in a sample is oxidized to nitrogen oxide at high temperatures in a pure oxygen stream and in the presence of a catalyst. Then nitrogen oxide is reduced to nitrogen with the help of copper and the side products water and carbon dioxide are separated in specific traps. Finally the amount of nitrogen is detected by a thermal conductitivity detector (TCD). The calibration ot the TCD is performed with a suitable substance with known nitrogen content.

2 Methods This application note is meant to be a guideline for the operation of your C. Gerhardt analysis system and has to be adapted to your sample matrix and the local circumstances in your laboratory. The document is based on

• DIN EN ISO 16634-1, Ölsaatenschrote und Futtermittel - Bestimmung des Gehaltes an Gesamtstickstoff nach dem Verbrennungsverfahren nach Dumas, 2009.

• AOAC 990.03, Protein (Crude) in Animal Feed, 2002.

3 Gases and Consumables The following gases and consumables are needed for the operation of DUMATHERM:

• Helium cylinder gas, quality min. 5.0 • Oxygen cylinder gas, quality min. 5.0 • Nitrogen or air cylinder gas, quality min. 2.6, resp. quality 1 acc. ISO 8573-1.

(free from moisture, particles or oil) • DumaReact®, combustion reactor, packed, 14-0245 • DumaCollect®, ash insert with bottom, 14-0015 • DumaTube®, quartz glass for reactor, 14-0203 • DumaPad®, quartz wool pads for reduction reactor filling, 14-0225 • DumaFoil®, tin foil for sample wrapping, 14-0017 • DumaCop®, copper for reduction, 14-0046 • DumaEDTA®, calibration standard, purity >99 %, 14-0032

4 Instruments • Analytical balance (accuracy at least 0.1 mg, preferably 0.01 mg) • 14-0400, DUMATHERM DT N Pro, with starter kit and consumables • High-speed rotor mill (Centrifugal mill), e.g. Fritsch PULVERISETTE 14, sieve

size 1 mm. • 14-0025, DT Encapsulating device for sample magazine 64-place

A. 2.2.1 Dumas Nitrogen in Feedstuff

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5 Procedure 5.1 Sample preparation and weighing Mill the commercially available feedstuff pellets with a centrifugal mill to 1 mm particle size. Keep the milled material in a closed container and mix it thoroughly shortly before weighing the samples:

Picture 1: Milling to 1 mm particle size and storage of the samples Weigh and wrap the samples into tin foil. Transfer the weighing data automatically into the software DUMATHERM-Manager after having wrapped the samples with tin foil. Then store the samples in the sample transfer magazine.

Packing Weighing Transfer 5.2 Analysis Before the analysis, activate DUMATHERM and perform the quality assurance described in the operating instructions of the instrument (Check-up maintenance, Check-up leak-test, Check-up blank value, Check-up standard). For the combustion analysis of grain samples we recommend the following settings:

Parameter Setting

Sample weight 300 mg +/- 2 mg

Sample packing Tin foil (alternatively paper which requires usage of DumaPress encapsulating tool 14-0025)

Combustion Method B 1,8 (with 1,8 ml O2 / mg sample dosing speed 300 ml/min)

Protein factor 6,25 (can be freely defined)

Combustion temperature 1030 °C

Reduction temperature 750 °C

A. 2.2.1 Dumas Nitrogen in Feedstuff

Application_A.2.2.1. Nitrogen in Feed Dumas_08.2020_english.doc • Rev.: A • Page 4 of 6

6 Evaluation 6.1 Exemplary results dog food Animal feed as pellets, milled to 1 mm sieve size. Initial sample weight approx. 300 mg.

Analyses with 300 mg initial sample weights will lead to peak areas of approximately 52000 mVs. This corresponds to 13.5 mg nitrogen absolute. For the calibration we recommend to perform a series of analysis with 10 EDTA samples with increasing weights in steps of 20 mg (starting with 10 mg EDTA up to 190 mg EDTA). According to DIN ISO 16634-1 a repeatability of sd < 0.03 is requested for the % N value. AOAC 992.23 allows a tolerance of sr < 0.15 for the protein value in %. The analysis results achieved with DUMATHERM are compliant and fullfill both requirements. 6.2 Exemplary results feedstuff for broilers, VDLUFA Ring test 2019 This sample was analysed by more than 20 laboratories following the combustion method with the following results:

Illustration 1: Ringtest evaluation, results of C. Gerhardt Application Laboratory are highlighted in the red frame. Above table shows the Dumas analysis results of the participating laboratories and the accepted tolerances (red horizontal lines).

A. 2.2.1 Dumas Nitrogen in Feedstuff

Application_A.2.2.1. Nitrogen in Feed Dumas_08.2020_english.doc • Rev.: A • Page 5 of 6

The original results achieved with DUMATHERM can be taken from the below table. Deviations from the ring test average value are due to moisture content correction. Taking the 10,5 % moisture into account, the Gerhardt results fits perfectly into the acceptance range of the Ringtest.

für N Standardabweichung

Durchflussraten:oC soC soC

Method :

N Gewicht[mg]

67956,25 3,741E+04 9,480 3,204 20,02

08.03.2019 13:54:36 6795

20,09

0,15

0,75

3,215

0,024

0,747

80319

Protein[%]

19,82

Stickstoff[%]

3,171

Seriennummer :Software Version:

Zeit

1005DUMATHERM MANAGER V8.07c

Gewicht[mg]

Kalibrierung nummerund standardname :

Operator :

Proteinfaktor

6,25 3,717E+04

Dumatherm Stickstoff / Protein Analysator

749ReduktionsreaktorVerbrennungsreaktor He(FC1):

Datum

He(FC2):

297,008

7

VDLUFA 1 2019 HeliumAuftraggeber :

RSA [%]

Durchschnitt

9,418

StickstoffPeakfläche

[mV*s]

200,0

EDTA

11Messverzögerung

Zeiten:

sccm Messung abbrechen

B1,8

Dr. Werner Küppers

Probenname

Entgasungsofen

08.03.2019

195,0 sccm

300,0300 O2

Default Calibration (L-L-L )

Temperaturen:

13:44:1908.03.2019 13:49:28 6795 295,882

Analysenzeit Autosccm

Feuchte [%]

1029

Seriesname :

3,233 20,2108.03.2019 13:59:42 6795 298,963 6,25 3,800E+04 9,627 3,220 20,13

298,108 6,25 3,804E+04 9,638

6,25 3,807E+04 9,645 3,226 20,1608.03.2019 14:04:47 6795 298,9926,25 3,832E+04 9,711 3,234 20,2108.03.2019 14:10:00 6795 300,268

Analyses with an initial sample weight of around 300 mg will lead to a peak area of approx. 38000 mVs. This corresponds to approx. 9.5 mg nitrogen absolute. For the calibration we recommend to perform a series of analysis of 10 EDTA samples with increasing weights in steps of 20 mg (starting with 10 mg EDTA up to 190 mg EDTA). According to DIN ISO 16634-1 a repeatability of sd < 0.03 is requested for the % N value. AOAC 992.23 allows a tolerance of sr < 0.15 for the protein value in %. The analysis results achieved with DUMATHERM are compliant and fullfill both requirements. If a better repeatability is requested, the sample should be be grinded more finely.

A. 2.2.1 Dumas Nitrogen in Feedstuff

Application_A.2.2.1. Nitrogen in Feed Dumas_08.2020_english.doc • Rev.: A • Page 6 of 6

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