1、BSI Standards PublicationBS ISO 19051:2015Rubber, raw natural, andrubber latex, natural Determination of nitrogencontent by Micro Dumascombustion methodBS ISO 19051:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 19051:2015.The UK participation in its prep
2、aration was entrusted to Technical Committee PRI/23, Test methods for rubber and non-black com-pounding ingredients.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contrac
3、t. Users are responsible for its correct application. The British Standards Institution 2015.Published by BSI Standards Limited 2015ISBN 978 0 580 85453 8ICS 83.040.10; 83.060Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under th
4、e authority of the Standards Policy and Strategy Committee on 31 May 2015.Amendments/corrigenda issued since publicationDate Text affectedBS ISO 19051:2015 ISO 2015Rubber, raw natural, and rubber latex, natural Determination of nitrogen content by Micro Dumas combustion methodLatex de caoutchouc bru
5、t Dtermination de la teneur en azote par la mthode de combustion de Micro DumaINTERNATIONAL STANDARDISO19051First edition2015-05-01Reference numberISO 19051:2015(E)BS ISO 19051:2015ISO 19051:2015(E)ii ISO 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2015, Published in SwitzerlandAll righ
6、ts reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from ei
7、ther ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 19051:2015ISO 19051:2015(E)Foreword ivIntroduction v1 Scope .
8、 12 Normative references 13 Principle 14 Reagents 25 Apparatus . 26 Calibration 37 Sampling and preparation of test piece 38 Procedure. 49 Test report . 5Annex A (normative) Calibration schedule . 7Annex B (informative) Technical justification of Micro Dumas combustion process 8 ISO 2015 All rights
9、reserved iiiContents PageBS ISO 19051:2015ISO 19051:2015(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committe
10、es. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the Inte
11、rnational Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the dif
12、ferent types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO sha
13、ll not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document i
14、s information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT)
15、 see the following URL: Foreword - Supplementary information.The committee responsible for this document is ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing and analysis.iv ISO 2015 All rights reservedBS ISO 19051:2015ISO 19051:2015(E)IntroductionThe Dumas combustion method has beco
16、me the most frequently used method worldwide for the accurate and fast determination of nitrogen. Compared to the wet chemical Kjeldahl method, it is superior in terms of speed, safety, and environmental friendliness. The representative analysis of a natural product requires a larger sample size of
17、up to 1 g or more.The nitrogen content of natural rubber is related to the protein level. The protein content of natural rubber varies depending upon its source and methods used in its processing. Generally, raw natural rubber is expected to have a nitrogen content in the range of 0,3 % to 0,6 %. Th
18、e normal latex grades have lower levels of nitrogen than the “dry” rubbers, with values around 0,2 %. However, “skim” rubber, with its high protein content, will have appreciably higher values, in the range of 1,5 % to 2,5 %.This test method will help determine the nitrogen content of the raw natura
19、l rubber in the shortest possible time and will be helpful for laboratory quality control testing. ISO 2015 All rights reserved vBS ISO 19051:2015BS ISO 19051:2015Rubber, raw natural, and rubber latex, natural Determination of nitrogen content by Micro Dumas combustion methodWARNING 1 Persons using
20、this International Standard should be familiar with normal laboratory practice. This International Standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure
21、 compliance with any national regulatory conditions.WARNING 2 Certain procedures specified in this International Standard might involve the use or generation of substances or the generation of waste that could constitute a local environmental hazard. Reference should be made to appropriate documenta
22、tion on safe handling and disposal after use.1 ScopeThis International Standard specifies a test method for the determination of nitrogen content of raw natural rubber using the Micro Dumas combustion method. This method is also applicable to natural rubber latex.2 Normative referencesThe following
23、documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 123, Rubber latex
24、SamplingISO 124:2014, Latex, rubber Determination of total solids contentISO 1795, Rubber, raw natural and raw synthetic Sampling and further preparative proceduresISO 18899:2013, Rubber Guide to the calibration of test equipment3 PrincipleIn the combustion process (furnace at ca. 1 000 C), nitrogen
25、 is converted to nitrogen gas/oxides. If other elements are present, they will also be converted to different combustion products. A variety of absorbents are used to remove these additional combustion products.The combustion products are swept out of the combustion chamber by an inert carrier gas s
26、uch as helium and passed over heated (about 600 C) high purity copper. This copper can be situated at the base of the combustion chamber or in a separate furnace. The function of this copper is to remove any oxygen not consumed in the initial combustion and to convert any oxides of nitrogen to nitro
27、gen gas. The gases are then passed through the absorbent traps.Detection of the gases can be carried out in a variety of ways, including the following:a) GC separation followed by quantification using thermal conductivity detection;b) partial separation by GC (“frontal chromatography”) followed by t
28、hermal conductivity detection;c) series of separate infrared and thermal conductivity cells for detection of individual compounds.INTERNATIONAL STANDARD ISO 19051:2015(E) ISO 2015 All rights reserved 1BS ISO 19051:2015ISO 19051:2015(E)Quantification of nitrogen requires calibration with high purity
29、“micro-analytical standard” standard reference compounds with known nitrogen content.During the combustion process, organic compounds are oxidized at high temperature to yield carbon dioxide, water, and oxides of nitrogen:CHNCompoundCOHONOO;1000 Cx222 +The oxides of nitrogen are then converted to ni
30、trogen gas in the presence of metallic copper:NO NxCu;600 C24 Reagents4.1 Helium (99,99 %), as carrier gas and high purity (99,99 %) oxygen as combustion gas.4.2 Analytical standards, as per Table 1.Table 1 Reference standardsSample Molecular formula Theoretical %C Theoretical %H Theoretical %N Theo
31、retical %STryptophan C11H12N2O264,69 % 5,92 % 13,72 % 0 %Imidazole C3H4N252,93 % 5,92 % 41,15 % 0 %Isatin C8H5NO265,31 % 3,43 % 9,52 % 0 %Alanine C3H7NO240,44 % 7,92 % 15,72 % 0 %Nicotinamide C6H6N2O 59,01 % 4,95 % 22,94 % 0 %Lysine C6H14N2O249,30 % 9,65 % 19,16 % 0 %Cyclohexanone C6H10O 73,43 % 10,
32、27 % 0 % 0 %Acetanilide C8H9NO 71,09 % 6,71 % 10,36 % 0 %Urea CH4N2O 20,00 % 6,71 % 46,65 % 0 %Atropine C17H23NO370,56 % 8,01 % 4,84 % 0 %Cystine C6H12N2O4S229,99 % 5,03 % 11,66 % 26,69 %Sulphanilamide C6H8N2O2S 41,84 % 4,68 % 16,27 % 18,62 %BBOT C26H26N2O2S 72,53 % 6,09 % 6,51 % 7,4 4 %5 Apparatus5
33、.1 Combustion elemental analysers are manufactured in a variety of configurations to suit specific applications and the choice will depend on the elements of interest, the sample type and size, and the concentration of the analyte.All instruments require two gas supplies: an inert carrier gas (heliu
34、m recommended) and high purity oxygen (minimum 99,99 %). The strict specification for oxygen and the carrier gas is associated with the need to reduce the nitrogen “blank” contribution to an inconsequential level. Additionally, GC-type gas filters are also usually fitted to prevent trace organic spe
35、cies and water entering the combustion system.The choice of test piece introduction system will depend on the application and the nature of the material. For solids or viscous liquids, the test pieces are weighed out into tin capsules. For liquids, the test pieces can be sealed in individual alumini
36、um vials or introduced through a liquid auto-sampler. Both capsules 2 ISO 2015 All rights reservedBS ISO 19051:2015ISO 19051:2015(E)and vials are pre-cleaned and dried to avoid trace contamination from oils and water acquired during their manufacture. Instruments are marketed with either simple “one
37、 shot” introduction interfaces or a carousel type auto-sampler. In some instances, a microbalance is directly interfaced with the analyser to allow the automatic recording of the weight of each test piece.The combustion section of the analyser is designed to achieve both complete combustion of the t
38、est piece and conversion of oxides of nitrogen to nitrogen gas (N2). Although different approaches have been chosen by different manufacturers, the use of high purity copper is universal for the reduction stage. In some instruments, the combustion and reduction stages are housed in separate furnaces
39、. In others, the reactions are combined in a single two-tier furnace. Catalysts are usually added to the combustion section to aid complete combustion along with absorbents to remove potential contaminants. Both the catalysts/absorbents and copper metal are packed into readily exchangeable tubes mad
40、e of ceramic material or high quality silica.The detection system within the analyser can take several forms depending on the combustion mode and test piece size. With small test pieces, the combustion gases can be separated on a GC column and quantified using a thermal conductivity detector. A sche
41、matic diagram of such a system is shown in Figure 1. If larger test pieces are required, an instrument employing “frontal” chromatography can be chosen. The latter approach employs a GC column with thermal conductivity detection but provides a step-wise profile for integration. Other detection appro
42、aches do not require a separation step but use separate infrared and thermal conductivity cells to respond to individual elements.Figure 1 Different components of elemental analyser (Micro Dumas method)5.2 Analytical balance, capable of weighing to the nearest 0,000 01 g.5.3 Micro syringe, calibrate
43、d.5.4 Test piece holder, generally, a tin capsule.6 CalibrationThe instrument shall be calibrated in accordance with the schedule given in Annex A.7 Sampling and preparation of test piece7.1 For the determination of nitrogen in raw solid rubber, take the laboratory sample in accordance with the meth
44、od specified in ISO 1795 and prepare the test piece from the laboratory sample. The test piece is to be cut into small thin pieces using suitable tools such as scissors or knife. ISO 2015 All rights reserved 3BS ISO 19051:2015ISO 19051:2015(E)7.2 For the determination of nitrogen in raw latex, take
45、the laboratory sample in accordance with ISO 123.To prepare the dried latex test piece, take an accurately weighed clean and dry aluminium foil dish. Measure 10 ml from the laboratory sample and put it in the aluminium foil dish. Put the aluminium foil dish in a 110 C vacuum oven and heat for 15 min
46、 until completely dry. Remove the aluminium foil dish from the oven and cool in a desiccator. If the dried sample becomes excessively sticky, sample can be dried at 70 C 2 C.A dried latex test piece can also be prepared in accordance with ISO 124:2013, 6.2.7.3 Weigh the test piece within the range o
47、f 0,50 mg to 1,50 mg using the analytical microbalance nearest to 1,00 mg 0,01 mg.7.4 Allow all the weighed test pieces and the analytical microbalance to equilibrate to room temperature for at least 30 min.7.5 Use a pair of tweezers to place an empty tin capsule on balance and tare the weight.7.6 R
48、emove the tin capsule using a pair of tweezers and place on metal sample prep block.7.7 Fill capsule with the desired test piece (generally 0,50 mg to 1,50 mg) and ensure that the test piece is fully encapsulated.7.8 Tap the encapsulated test piece on a clean surface to remove any remnants on the ou
49、tside of the encapsulated test piece.7.9 Place the encapsulated test piece on the balance and record the weight.7.10 Put the encapsulated test piece in numbered sample tray.8 Procedure8.1 GeneralTurn on the power to the instrument as per instruction of the instrument manufacturer.8.2 Equipment check8.2.1 Blank runa) It is used to establish the instrumental readings for carbon, hydrogen, nitrogen, and sulfur, so as to apply the required correction during the actual test run. It also indicates the stability of the s
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