1、August 2013 Translation by DIN-Sprachendienst.English price group 9No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS
2、67.100.99!%(“2052794www.din.deDDIN EN ISO 12779Lactose Determination of water content Karl Fischer method (ISO 12779:2011);English version EN ISO 12779:2013,English translation of DIN EN ISO 12779:2013-08Lactose Bestimmung des Wassergehaltes Karl-Fischer-Verfahren (ISO 12779:2011);Englische Fassung
3、EN ISO 12779:2013,Englische bersetzung von DIN EN ISO 12779:2013-08Lactose Dtermination de la teneur en eau Mthode de Karl Fischer (ISO 12779:2011);Version anglaise EN ISO 12779:2013,Traduction anglaise de DIN EN ISO 12779:2013-08www.beuth.deDocument comprises pagesIn case of doubt, the German-langu
4、age original shall be considered authoritative.1408.13 DIN EN ISO 12779:2013-08 2 A comma is used as the decimal marker. National foreword The text of ISO 12779:2011 has been prepared by Technical Committee ISO/TC 34 “Food products” (Secretariat: AFNOR, France), Subcommittee SC 5 “Milk and milk prod
5、ucts” (Secretariat: NEN, Netherlands) and has been taken over as EN ISO 12779:2013 by Technical Committee CEN/TC 302 “Milk and milk products Methods of sampling and analysis” (Secretariat: NEN, Netherlands). The responsible German body involved in its preparation was the Normenausschuss Lebensmittel
6、 und landwirtschaftliche Produkte (Food and Agricultural Products Standards Committee), Working Committee NA 057-05-13 AA Milch und Milcherzeugnisse Probenahme- und Untersuchungsverfahren. The DIN Standards corresponding to the International Standards referred to in this document are as follows: ISO
7、 707 DIN EN ISO 707 ISO 5725-1 DIN ISO 5725-1 ISO 5725-2 DIN ISO 5725-2 National Annex NA (informative) Bibliography DIN EN ISO 707, Milk and milk products Guidance on sampling DIN ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results Part 1: General principles and definit
8、ions DIN ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 12779 May 2013 ICS 67.100.99 English Ver
9、sion Lactose - Determination of water content - Karl Fischer method (ISO 12779:2011) Lactose - Dtermination de la teneur en eau - Mthode de Karl Fischer (ISO 12779:2011) Lactose - Bestimmung des Wassergehaltes - Karl-Fischer-Verfahren (ISO 12779:2011) This European Standard was approved by CEN on 16
10、 May 2013. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be ob
11、tained on application to the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the
12、CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Irela
13、nd, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue M
14、arnix 17, B-1000 Brussels 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 12779:2013: EContents DIN EN ISO 12779:2013-08 EN ISO 12779:2013 (E) 2 Page Foreword 3 1 Scope 4 2 Principle 4 3 Reagents .4 4 Apparatus .5 5 Sampli
15、ng .5 6 Procedure .5 7 Calculation and expression of results .8 8 Precision .9 9 Test report 9 Annex A (informative) Interlaboratory trial .11 Bibliography 12 Foreword The text of ISO 12779:2011 has been prepared by Technical Committee ISO/TC 34 “Food products” of the International Organization for
16、Standardization (ISO) and has been taken over as EN ISO 12779:2013 by Technical Committee CEN/TC 302 “Milk and milk products - Methods of sampling and analysis” the secretariat of which is held by NEN. This European Standard shall be given the status of a national standard, either by publication of
17、an identical text or by endorsement, at the latest by November 2013, and conflicting national standards shall be withdrawn at the latest by November 2013. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall no
18、t be held responsible for identifying any or all such patent rights. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark,
19、 Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement notice
20、 The text of ISO 12779:2011 has been approved by CEN as EN ISO 12779:2013 without any modification. DIN EN ISO 12779:2013-08 EN ISO 12779:2013 (E) 3 1 Scope This International Standard specifies a method for the determination of the water content of lactose by Karl Fischer (KF) titration. 2 Principl
21、e The test sample is directly titrated with a commercially available two-component Karl Fischer reagent. The water content is calculated from the amount of reagent used. Titration at a temperature of approximately 40 C gives shorter titration times and sharper end points. Only at this or higher temp
22、eratures is the use of a one-component Karl Fischer reagent (3.1) recommended. 3 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and only distilled or demineralized water or water of equivalent purity. Avoid absorption of moisture from the environment. 3.1 Karl
23、 Fischer (KF) reagent1). The KF reagent is a commercially available pyridine-free two-component reagent consisting of a titration component (3.2) and a solvent component (3.3). The titration component (3.2) is a methanolic solution of iodine and the solvent component (3.3) is a methanolic solution o
24、f sulfur dioxide and an appropriate base (e.g. imidazole). Alternatively, a pyridine-free one-component KF reagent can also be used which only consists of a titration component. The titration component (3.2) is a solution of iodine, sulfur dioxide and an appropriate base (e.g. imidazole) in a suitab
25、le solvent (e.g. diethylene glycol monoethyl ether). The solvent component (3.3) is methanol (3.5). This combination of a one-component titration reagent and methanol is only recommended if the titration is carried out at a temperature of approximately 40 C or higher. 3.2 Titration component. The ti
26、tration component of the KF reagent (3.1) shall have a water equivalent of approximately 2 mg/ml of water. A KF reagent with a water equivalent of approximately 5 mg/ml of water is also possible if a KF apparatus with a burette of capacity 5 ml is used (4.1). 3.3 Solvent component. The solvent compo
27、nent of the KF reagent as specified in 3.1. 3.4 Water standard, w(H2O) = 10 mg/g. 1) Hydranal-Titrant 2/Hydranal-Solvent from Sigma-Aldrich and apuraTitrant 2/apuraSolvent from Merck are examples of commercially available two-component systems. Hydranal-Composite 2 from Sigma-Aldrich and apuraCombiT
28、itrant 2 from Merck are examples of commercially available one-component reagents. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO and IDF of these products. DIN EN ISO 12779:2013-08 EN ISO 12779:2013 (E) 4 For the determination o
29、f the water equivalent of the titration component, use a commercially available liquid water standard containing 10 mg/g of water. 3.5 Methanol (CH3OH), with a mass fraction of water of not more than 0,05 %. 4 Apparatus Usual laboratory apparatus and, in particular, the following. Equipment shall be
30、 completely dry when used. 4.1 Karl Fischer (KF) apparatus. Use an automatic volumetric KF apparatus, preferably with a burette of capacity 10 ml. The burette should be of capacity 5 ml if a KF reagent with a water equivalent of approximately 5 mg/ml of water is used (see 3.2). For quicker titration
31、s at approximately 40 C, use a double-jacketed titration vessel with a water inlet and outlet to carry out the titration. 4.2 Water bath, capable of maintaining a water temperature of 40 C 5 C under thermostatic control, with a pump for heating the double-jacketed titration vessel of the KF apparatu
32、s (4.1). NOTE The use of a water bath with thermostatic control is only necessary if the titrations are carried out at temperatures above room temperature. 4.3 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg. 4.4 Disposable syringes, of capacity 5 ml or 10 m
33、l, for quantifying the water standard (3.4). 4.5 Glass weighing spoon, for dosing the test sample. 5 Sampling A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. Sampling is not part of the method specified in this
34、International Standard. A recommended sampling method is given in ISO 707 IDF 501. 6 Procedure 6.1 KF apparatus drift 6.1.1 Determine the drift of the KF apparatus (4.1) every day and/or when the working conditions change as follows. Add to the titration vessel of the KF apparatus (4.1) approximatel
35、y 30 ml of solvent component (3.3). Pre-titrate the solvent component. Then carry out a titration over 5 min (without addition of a test sample). If determinations (6.5) are carried out at 40 C, heat the vessel and its contents using the water bath (4.2) to 40 C before pre-titrating the solvent comp
36、onent and carrying out the titration without addition of a test sample. IMPORTANT During each titration, the amount of solvent component used shall completely cover the electrodes of the KF apparatus. DIN EN ISO 12779:2013-08 EN ISO 12779:2013 (E) 5 6.1.2 Calculate the KF apparatus drift, qV, in mil
37、lilitres per minute, by using Equation (1): dVVqt (1) where Vdis the volume, in millilitres, of the titration component (3.2) in the titration (6.1.1); t is the numerical value, in minutes, of the time. Alternatively, calculate the KF apparatus drift, qm, in milligrams of water per minute, by using
38、Equation (2): demVqt (2) where eis the water equivalent (6.2) of the titration component (3.2), in milligrams of water per millilitre, used in the titration (6.1.1). 6.2 Water equivalent of the titration component of the KF reagent 6.2.1 Titration To calculate the water equivalent of the titration c
39、omponent, e, accurately carry out the titration in this subclause and the calculation step (6.2.2) five times. Add approximately 30 ml solvent component (3.3) to the titration vessel of the KF apparatus (4.1) (see also 6.1.1) and pre-titrate the solvent component. NOTE The water equivalent of the ti
40、tration component does not depend on temperature. It is therefore not necessary to heat the titration vessel for water equivalent determinations. If determinations (6.5) are carried out at 40 C, the water equivalent can also be determined at 40 C. In that case, the vessel and its contents are heated
41、 to 40 C using the water bath (4.2) before carrying out titrations. Into a disposable syringe (4.4), take up between 0,6 g to 0,9 g of the water standard (3.4) (an amount of between 6 mg and 9 mg water). Weigh the syringe and its contents, recording the mass to the nearest 0,1 mg. It is also possibl
42、e to take up more than 0,6 g to 0,9 g of the water standard and to use the same contents of the syringe for several titrations, but it is then important to carry out the titrations immediately one after the other. In this case, approximately 0,6 g to 0,9 g of the water standard should also be used f
43、or each titration, the exact amount being calculated each time by weighing the syringe and its remaining contents after each injection. NOTE Only for very experienced laboratories is it possible to use a small amount (approximately one drop from a syringe) of pure water instead of a commercial water
44、 standard. Even slight weighing errors lead to massive deviations of the result since they have an effect of 100 %. Add the amount of water standard in the syringe to the titration vessel. Weigh the empty syringe again, recording its mass to the nearest 0,1 mg. Subtract the mass of the empty syringe
45、 from that of the syringe with the water standard before addition of the water standard to the vessel to obtain the net mass of the water standard added to the titration vessel. Record the net mass, , to the nearest 0,1 mg, of added water standard for each titration (i = 1 5). 2HOimCarry out a titra
46、tion while using as shut-off criterion the 10 s stop delay time mentioned in 6.3. Record, for i = 1 5, the volume, , in millilitres, of the titration component used. e,iVDIN EN ISO 12779:2013-08 EN ISO 12779:2013 (E) 6 Do not perform more than three titrations on one portion of solvent component. Af
47、ter three titrations on one portion, empty the titration vessel and carry out further titrations by again adding to the titration vessel of the KF apparatus approximately 30 ml solvent component, pre-titrating the solvent component and proceeding in the same way as before. 6.2.2 Calculation Calculat
48、e the water equivalent of the titration component, e,i, in milligrams of water per millilitre, by using Equation (3): 22e,HO HO,e,iisimwV (3) where 2HOim is the mass, in grams, of the water standard used for titration i (6.2.1); 2HO,sw is the water mass fraction, in milligrams per gram, of the water standard; e,iVis the volume, in millilitres, of the titration component (3.2) in titration i (6.2.1). 6.2.3 Mean value Calculate the water equivalent of the titration component, e, expressed in milligrams
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