1、DRAFT FOR DEVELOPMENT DD ENV 12142:1997 Method for Determination of stable hydrogen isotope ratio( 2 H/ 1 H) of water from fruit juices, using isotope ratio mass spectrometry ICS 67.160.20DD ENV 12142:1997 This Draft for Development, having been prepared under the direction of the Consumer Products
2、and Services Sector Board, was published under the authority of the Standards Board and comes into effect on 15 February 1997 BSI 12-1998 The following BSI reference relates to the work on this Draft for Development: Committee reference AW/21 ISBN 0 580 27020 3 Committees responsible for this Draft
3、for Development The preparation of this Draft for Development was entrusted to Technical Committee AW/21, Fruit and vegetable juices, upon which the following bodies were represented: British Fruit Juice Importers Association British Retail Consortium British Soft Drinks Association Limited Campden
4、and Chorleywood Food Research Association Department of Trade and Industry (Laboratory of the Government Chemist) Leatherhead Food Research Association Ministry of Agriculture, Fisheries and Food Royal Society of Chemistry Amendments issued since publication Amd. No. Date CommentsDD ENV 12142:1997 B
5、SI 12-1998 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of ENV 12142 3 List of references Inside back coverDD ENV 12142:1997 ii BSI 12-1998 National foreword This Draft for Development has been prepared by Technical Committee AW/21, and is the Englis
6、h language version of ENV 12142:1996 Fruit and vegetable juices Determination of the stable hydrogen isotope ratio ( 2 H/ 1 H) of water from fruit juices Method using isotope ratio mass spectrometry,published by the European Committee for Standardization (CEN). ENV 12142:1996 was produced as a resul
7、t of international discussions in which the United Kingdom took an active part. This publication is not to be regarded as a British Standard It is being issued in the Draft for Development series of publications and is of a provisional nature. It should be applied on this provisional basis so that i
8、nformation and experience of its practical application may be obtained. Comments arising from the use of this Draft for Development are requested so that UK experience can be reported to the European organization responsible for its conversion to a European Standard. A review of this publication wil
9、l be initiated 2years after its publication by the European organization so that a decision can be taken on its status at the end of its 3-year life. The commencement of the review period will be notified by an announcement in BSI Update. According to the replies received by the end of the review pe
10、riod, the responsible BSI Committee will decide whether to support the conversion into a European Standard, to extend the life of the prestandard or to withdraw it. Comments should be sent in writing to the Secretary of BSI Technical Committee AW/21 at BSI, 389 Chiswick High Road, London W4 4AL, giv
11、ing the document reference and clause number and proposing, where possible, an appropriate revision of the text. Cross-references ISO 5725:1986, to which informative reference is made in the text, has been superseded by ISO 5725-1:1994, ISO 5725-2:1994, ISO 5725-3:1994, ISO5725-4:1994 and ISO 5725-6
12、:1994, which are identical with the following Parts of BS ISO 5725 Accuracy (trueness and precision) of measurement methods and results: BS ISO 5725-1:1994, General principles and definitions. BS ISO 5725-2:1994, Basic method for the determination of repeatability and reproducibility of a standard m
13、easurement method. BS ISO 5725-3:1994, Intermediate measures of the precision of a standard measurement method. BS ISO 5725-4:1994, Basic method for the determination of the trueness of a standard measurement method. BS ISO 5725-6:1994, Use in practice of accuracy values. Summary of pages This docum
14、ent comprises a front cover, an inside front cover, pages i and ii, theENV title page, pages 2 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front c
15、over.EUROPEAN PRESTANDARD PRNORME EUROPENNE EUROPISCHE VORNORM ENV 12142 October 1996 ICS 67.160.20 Descriptors: Food products, beverages, fruit and vegetable juices, chemical analysis, determination, ratios, isotopes, hydrogen, mass spectrometry English version Fruit and vegetable juices Determinat
16、ion of the stable hydrogen isotope ratio ( 2 H/ 1 H) of water from fruit juices Method using isotope ratio mass spectrometry Jus de fruits et de lgumes Dtermination du rapport des isotopes stables en hydrogne ( 2 H/ 1 H) dans leau des jus de fruits Mthode utilisant la spectromtrie de masse des rappo
17、rts isotopiques Frucht- und Gemsesfte Bestimmung des Verhltnisses der stabilen Wasserstoff-Isotope ( 2 H/ 1 H) im Wasseranteil von Fruchtsften Verfahren unter verwendung der Isotopenverhltnis-Massenspektrometrie This European Prestandard (ENV) was approved by CEN on 1996-02-29 as a prospective stand
18、ard for provisional application. The period of validity of this ENV is limited initially to three years. After two years the members of CEN will be requested to submit their comments, particularly on the question whether the ENV can be converted into an European Standard (EN). CEN members are requir
19、ed to announce the existance of this ENV in the same way as for an EN and to make the ENV available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the ENV) until the final decision about the possible conversion of
20、the ENV into an EN is reached. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, IceLand, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization C
21、omit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1996 Copyright reserved to CEN members Ref. No. ENV 12142:1996 EENV 12142:1996 2 BSI 12-1998 Foreword This European Prestandard has been prepared by the Technical Committee CEN/TC 17
22、4 “Fruit and vegetable juices Methods of analysis” of which the Secretariat is held by AFNOR. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are required to announce the existence of this European Prestandard: Austria, Belgium, Denm
23、ark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Contents Page Foreword 2 1 Scope 3 2 Normative references 3 3 Symbols and abbreviations 3 4 Principle 3 5 Reagents 3 6 Apparatus 3 7 Procedure
24、 4 8 Calculation 4 9 Precision 4 10 Test report 5 Annex A (informative) Bibliography 6 Annex B (informative) Device for microcryotrapping 7 Annex C (informative) Statistical results of the interlaboratory test 7 Figure B.1 7 Table C.1 8ENV 12142:1996 BSI 12-1998 3 1 Scope This European Prestandard s
25、pecifies a method for the determination of the stable hydrogen isotope ratio ( 2 H/ 1 H) of water from fruit juices by isotope ratio mass spectrometry (IRMS). 2 Normative references This European Prestandard incorporates by dated or undated reference, provisions from other publications. These normat
26、ive references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Prestandard only when incorporated in it by amendment or revision. For undated ref
27、erences the latest edition of the publication referred to applies. ISO 5725:1986, Precision of the test methods Determination of repeatability and reproducibility for a standard test method by inter-laboratory tests. 3 Symbols and abbreviations For the purposes of this standard the following symbols
28、 and abbreviations apply: 4 Principle The deuterium ( 2 H) content of water is determined by applying isotope mass spectrometric measurements of the intensities of the ions having a mass of 2 ( 1 H 2 ) and of 3 ( 1 H 2 H) on hydrogen gas obtained by the reduction of water. 5 Reagents 5.1 Nuclear pur
29、e Uranium 238 1, 2 or zinc alloy 3 which is suitable for water reduction. Uranium and zinc shall be pre-treated before use as follows. Wash with hydrochloric or nitric acid, and then wash with water. Dry and degass metal carefully. For zinc, the degassing should take approximately 30min to 40min at
30、180C. WARNING: Uranium 238, when heated at 800C, releases toxic vapours. Do not stand near the oven(6.2). 5.2 SMOW and SLAP reference waters (obtainable from the International Atomic Energy Agency, (IAEA) 1) ) 4. 5.3 Hydrogen gas of analytical quality. 6 Apparatus Usual laboratory apparatus and, in
31、particular, the following: 6.1 Isotope ratio mass spectrometer, with the ability to determine the 2 H content of hydrogen gas at natural abundance with an internal precision of0,1 or better (expressed in relative d value (see8). The internal precision is here defined as the difference beetwen two me
32、asurements of the same hydrogen sample. This instrument should comprise: a double collector allowing simultaneous collection of the ions having respective masses of2 and 3; a dual inlet system for the introduction of the gases into the mass spectrometer which enables the repeated, alternating measur
33、ement of a reference hydrogen gas and the hydrogen gas resulting from the reduction of a water sample; an electronic compensation system for calculation and elimination of the amount of 1 H 3 +ions having been formed in the mass spectrometer and being measured together with 1 H 2 H at mass3. 6.2 App
34、aratus for the reduction of water samples and the collection of hydrogen gas for the isotopic analysis comprising: an oven containing 20g to 40g of uranium(5.1) maintained at a temperature of800C; or a reduction container made of special glass and filled with 0,3g of suitable zinc alloy(5.1) which c
35、an be heated to 450C to455C for 30min to 60min. ( 2 H/ 1 H) Isotopic ratio of deuterium to hydrogen of mass 1 for a considered sample; (d 2 H Deuterium ( 2 H) content expressed in parts per thousand (); SMOW Standard Mean Ocean Water; SLAP Standard Light Antartic Precipitation; GISP Greenland Ice Sh
36、eet Precipitation; g Acceleration due to gravity at the surface of the earth (9,81 m/s 2 ); 1) International Atomic Energy Agency P.O. Box 100 A 1400 Wien AUSTRIAENV 12142:1996 4 BSI 12-1998 when using uranium a system for trapping the hydrogen gas released by the reduction of the water. A TOEPLER p
37、ump 5 is ideally suited for this application or a trapping system may be chosen, using uranium at 60C 6. This enables the hydrogen gas to be collected in a sample bottle which can then be connected up to the inlet system of the mass spectrometer. 6.3 Sample bottles, which can be adequately sealed un
38、der vacuum. 6.4 Pumping system, capable of obtaining a vacuum of 0,13Pa during the sample preparation. 6.5 Centrifuge, capable of producing a centrifugal acceleration of 1400g at the base of the centrifuge tube (6.6). NOTEThe rotational frequency required to give correct centrifugal acceleration can
39、 be calculated from the following equation: where: 6.6 Centrifuge tubes 7 Procedure 7.1 Sample preparation Centrifuge (6.5) 25ml of the fruit juice for 10min at1400g. 7.2 Distillation in a closed vessel Perform a microdistillation to separate the fruit juice water from organic compounds (sugar, acid
40、s, lipids) with quantitative recovery of the water (reaction of the raw juices with zinc or uranium will not produce hydrogen gas with the same deuterium content as the water of the fruit juice). For the details of the microdistillation process, seefigure inB1. A distillation under static vacuum may
41、 also be performed by using a special piece of distillation equipment called Rittenberg “trousers” on 2ml to3ml of juice. This process always gives a quantitative recovery of the water. 7.3 Reduction Use 10l of sample(7.2) and a reduction time of at least 15min when employing uranium (5.1). Use betw
42、een 5l to 10l of sample (7.2) and a reduction time of 30min to 60min when employing the zinc(5.1) method. The hydrogen gas obtained is collected in sample bottles (6.3). 7.4 Determination Connect the sample bottles (6.3) to the mass spectrometer (6.1) and measure the relative difference in parts per
43、 thousand of deuterium content between the sample hydrogen gas and a reference hydrogen gas (5.3) using the following equation: 7.5 Calibration In accordance with 7.3 and 7.4 carry out the same determination on the two reference waters (SMOW and SLAP (5.2) and determine d 2 H SMOW and d 2 H SLAP wit
44、h respect to the reference hydrogen gas 8 Calculation Express the deuterium content of the water of the fruit juice with respect to the SMOW reference water by the following equation: The accepted value for the SLAP reference water is d 2 H = 428 SMOW4. 9 Precision Details of the interlaboratory tes
45、t on precision of the method are summarized in annexC. The values derived from the interlaboratory test may not be applicable to analyte concentration ranges and matrices other than given inAnnexC. (1) a is the centrifugal acceleration r is the radius of the centrifuge in centimetres, measured from
46、the mid point (the centrifuge axis) to the bottom of the centrifuge tube when swung out; n is the rotational frequency per minute. a 11,18rn1000 () 2 = (2) (3) d sample H 2 / H 1 () sample H 2 / H 1 () reference -1 1000 = d 2 H sample d sample d SMOW d SMOW d SLAP -428 =ENV 12142:1996 BSI 12-1998 5
47、9.1 Repeatability The absolute difference between two single results found on identical test material by one operator using the same apparatus within the shortest feasible time interval will exceed the repeatability limit r in not more than 5% of the cases. The values are: Orange juice r = 3,69 ; Ap
48、ple juice r = 3,95 GISP 2)water r = 3,47 ; Laboratory water 3) r = 3,21 . 9.2 Reproducibility The absolute differences between two single test results on identical test material reported by two laboratories will exceed the reproducibility limit R in not more than 5% of the cases. The values are: Ora
49、nge juice R = 3,69 ; Apple juice R = 3,95 ; GISP 2)water R = 6.94 ; Laboratory water 3) R = 6.24 . 10 Test report The test report shall contain the following data: all information necessary for the identification of the sample (kind of sample, origin of sample, designation); a reference to this European Standard; date and type of sampling procedure (if known); the date o
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1