土壤中氮素检测方案(定氮仪)

APPLICATION NOTEF&F-D-004-2016/A1 N/PROTEIN DETERMINATION IN SOILS N/Protein Determination in Soilsaccording to the Dumas method (He/Ar as Carrier) Reference： AOAC 993.13 Nitrogen (Total) in Fertilizers ISO 13878：1998 Soil quality -- Determination of total nitrogen contentby dry combustion ("elemental analysis") Tested with VELP Scientifica NDA 702 Dual Carrier Gas Dumas Nitrogen Analyzer (Code F30800080) DUMAS COMBUSTION METHOD Introduction The nitrogen in plants is a part of numerous compounds， including proteins， enzymes，nucleic acids，chlorophyll andvitamins essential for all biological functions. It is taken from soil or from air， and it can be used only through a specified and complex chemical process callednitrogen cycle. The performance of the VELP NDA 702 was evaluated by participating in the Proficiency Testing program organized byWEPAL (Wageningen Evaluating Programs for Analytical Laboratories). Samples of soil were analyzed using the NDA 702 and the results obtained (as % Nitrogen) were compared with thestatistical range accepted by WEPAL. Nitrogen Determination in Soils The Dumas method starts with a combustion furnace (CF) to burn thesample， obtaining elemental compounds. Water is removed by a first physical trap (WT1 - DriStepTM)， placed afterthe combustion， and a second chemical one (WT2). Between the two， theelemental substances passed through a reduction furnace (RF). The auto-regenerative CO2 absorbers (CO2) let pass only the elementalnitrogen that is detected by the LoGas TM innovative Thermal ConductivityDetector (TCD) with no requirement for a reference gas. The NDA 702 is controlled through the intuitive DUMASoftTM. NDA 702 Preliminary Operations (daily) Follow the operating manual to start the NDA 702 and check that the following parameters are set： Temperature Combustion reactor (Code A00000158)：1030°C Temperature Reduction reactor (Code A00000226)： 650°C Flow rate MFC1 Carrier gas (He/Ar)： 190 ml/min Flow rate MFC2 Carrier gas (He/Ar)： 220 ml/min Condition the system by testing 2 EDTA standard (Code A00000149) and 3 to 5 empty tin foils (Code A00000153) asCheck up. Verify the calibration curve with one or more tests as Standard by testing the same standard used for the curve creation.Use the quartz ash insert (Code A00000161). Sample Preparation Using a spatula， put 300 mg of Soils Reference Material into the tin foil. Close the tin foil， obtaining a capsule and load the capsule into the autosampler. Analysis Procedure Fill the following fields in the database： Sample name， Weight， Method， Sample type， Calibration number Use the “Soil” method with the following parameters： O2 flow rate： 400 ml/min O2 factor： 0.7 ml/mg Press to start the analysis. Analysis time： from 3 minutes for one run. Sample HELIUM as Carrier Gas ARGON as Carrier Gas Range of %N quantity (mg) N% quantity (mg) N% Soil 1 (code WEPAL 2015.4_870) 299.10 0.165 299.85 0.161 305.75 0.163 301.53 0.161 300.22 0.164 302.52 0.162 Average±SD% 0.164±0.001 Average±SD% 0.161±0.001 0.146-0.166 RSD%* 0.609 RSD%* 0.358 Soil 2 (code WEPAL 2015.4_861) 303.53 0.163 301.74 0.159 300.34 0.164 304.62 0.161 300.16 0.162 303.05 0.162 Average±SD% 0.163±0.001 Average±SD% 0.161±0.002 0.150-0.180 RSD%* 0.613 RSD%* 0.951 Soil 3 (code WEPAL 2015.4_860) 304.38 0.169 304.35 0.166 300.00 0.170 304.11 0.166 301.34 0.169 305.11 0.168 Average ± SD% 0.169±0.001 Average ± SD% 0.167±0.001 0.147-0.175 RSD%* 0.341 RSD%* 0.693 Soil 4 (code WEPAL 2015.4_919) 305.95 0.153 305.95 0.156 300.13 0.152 301.85 0.153 299.78 0.150 302.36 0.154 Average±SD% 0.152±0.002 Average±SD% 0.154±0.002 0.139-0.165 RSD%* 1.007 RSD%* 0.990 *RSD%=(Standard Deviation *100)/ Average Conclusion Results are extremely reliable and reproducible， as demonstrated by the RSD， by using helium or argon as carrier gas，with the same conditions (method and sample weight) since the goal is to obtain < 2.0% relative standard deviation， asrequested by official methods. The obtained values fell within the expected nitrogen range of each standard materialcertified by WEPAL， demonstrating the high performance of NDA702. Helium remains the best choice for premium accuracy but its shortages and interruptions are affecting any relatedproduct or instrument， including elemental analyzers. Argon， the best alternative available， has demonstrated to be avalid substitute， ensuring optimal results. VELP Scientifica NDA 702 Dual Carrier Gas Dumas Nitrogen Analyzer is theperfect response to simple， fast and precise nitrogen/protein determination， both with Helium and Argon as carrier gas. Copyright C VELP Scientifica.All rights reserved.No part of this publication may be reproduced or transmitted in any form or for any purpose without the express permission of VELP.VELP Scientifica， Italy Tel： + Fax： + www.velp.com 利用VELP NDA 702杜马斯定氮法测定土壤中的氮素含量:植物中的氮是许多化合物的一部分，包括蛋白质，酶，核酸，叶绿素和所有生物功能所必需的维生素。 它取自土壤或空气，只能通过特定的复杂化学过程（称为氮循环）使用。 VELP NDA 702的性能是通过参加WEPAL组织的能力测试计划（分析实验室的Wageningen评估计划）来评估的。使用NDA 702分析土壤样品，并将获得的结果（以氮含量计）与WEPAL接受的统计范围进行比较。本文介绍了利用杜马斯燃烧法进行土壤中的氮素分析。