1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 12133 : 1998 The Eu
2、ropean Standard EN 12133 : 1997 has the status of a British Standard ICS 67.160.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Fruit and vegetable juices Determination of chloride content Potentiometric titration methodThis British Standard, having been prepared under the
3、direction of the Consumer Products and Services Sector Board, was published under the authority of the Standards Board and comes into effect on 15 February 1998 BSI 1998 ISBN 0 580 28968 0 BS EN 12133 : 1998 Amendments issued since publication Amd. No. Date Text affected National foreword This Briti
4、sh Standard is the English language version of EN 12133. The UK participation in its preparation was entrusted to Technical Committee AW/21, Fruit and vegetable juices, which has the responsibility to: aid enquirers to understand the text; present to the responsible European committee any enquiries
5、on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British S
6、tandards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled International Standards Correspondence Index, or by using the Find facility of the BSI Standards Electronic Catalogue. Compliance with a
7、 British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 6, an inside back cover and a back cover.CEN European Committee for Standardization Comite Europe en de Normalisat
8、ion Europa isches Komitee fu r Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1997 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12133 : 1997 E EUROPEAN STANDARD EN 12133 NORME EUROPE ENNE EUROPA ISCHE NORM Sept
9、ember 1997 ICS 67.160.20 Descriptors: Fruit and vegetables juices, chemical analysis, determination of content, chlorides, potentiometric methods, procedures English version Fruit and vegetable juices Determination of chloride content Potentiometric titration method Jus de fruits et de le gumes Dosa
10、ge des chlorures Me thode de titrage potentiome trique Frucht- und Gemu sesa fte Bestimmung des Chloridgehaltes Potentiometrisches Titrationsverfahren This European Standard was approved by CEN on 6 September 1997. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipu
11、late 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 obtained on application to the Central Secretariat or to any CEN member. This European Standard ex
12、ists 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 Central Secretariat has the same status as the official versions. CEN members are the national standards b
13、odies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.Page 2 EN 12133 : 1997 BSI 1998 Foreword This European Standard has been prepared by Technical Commi
14、ttee CEN/TC 174, Fruit and vegetable juices Methods of analysis, the Secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by March 1998, and conflicting national sta
15、ndards shall be withdrawn at the latest by March 1998. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Icelan
16、d, 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 3 4 Principle 3 5 Reagents 3 6 Apparatus 3 7 Procedure 3 8 Calculation 4 9 Precision 5 10 Test report 5 Annexes A (in
17、formative) Bibliography 6 B (informative) Statistical results of the inter-laboratory test 6Page 3 EN 12133 : 1997 BSI 1998 1 Scope This European Standard specifies a potentiometric titration method for the determination of the chloride content of fruit and vegetable juices and related products. 2 N
18、ormative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions
19、 of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN ISO 3696 : 1995 Water for analytical laboratory use Specification and test methods (ISO 3696 : 198
20、7) ISO 5725 : 1986 Precision of test methods Determination of repeatability and reproducibility for a standard test method by inter- laboratory tests 3 Symbols For the purposes of this European Standard, the following symbols apply: c substance concentration r mass concentration v mass fraction d sp
21、ecific gravity n the volume in millilitres of the silver nitrate standard solution used to titrate the chloride content of the fruit juice sample using the end potential method V volume of standard solution at the equivalence point V9 volume of standard solution added before the potential rise DV i
22、constant volume for addition of the standard solution, (e.g. 0,2 ml) DE first potential difference DDE second potential difference DDE 1 second potential difference before the biggest potential rise DDE 2 second potential difference after the biggest potential rise 4 Principle The chloride content i
23、s determined by potentiometric titration using a silver/silver chloride electrode. 5 Reagents 5.1 General Use only reagents of recognized analytical grade and only water in accordance with at least grade 2 of EN ISO 3696 : 1995. 5.2 Potassium chloride The potassium chloride shall contain no more tha
24、n 0,005 % (m/m) bromide and shall be dried for three to four days in a desiccator before use. 5.3 Nitric acid, v(HNO 3 ) $ 65 g/100 g, d$ 1,4. 5.4 Potassium chloride solution, r(KCl) = 1,8636 g/l. Dissolve 1,8636 g of potassium chloride (5.2)i n1lo f water (5.1). 1 ml of this solution contains 0,886
25、 mg of chloride. 5.5 Silver nitrate standard solution, c(AgNO 3 ) = 0,025 mol/l. 1 ml of this solution reacts with 0,886 mg of chloride. 6 Apparatus Usual laboratory apparatus and, in particular, the following: 6.1 pH-millivoltmeter, readable to at least 2 mV. 6.2 Magnetic stirrer. 6.3 Ag/AgCl elect
26、rode, with saturated potassium nitrate solution as electrolyte. 6.4 Micro-burette, readable to at least 0,01 ml. 7 Procedure 7.1 Preparation of the test sample Normally products shall not be pre-treated, however dilution may be necessary and their analysis by this method shall be on a volumetric bas
27、is, results being expressed per litre of sample. The analysis of concentrated products may also be carried out on a volumetric basis, after dilution to a known relative density. In this case, the relative density shall be indicated. Based on a weighed sample and taking the dilution factor for analys
28、is into account, the results may also be expressed per kilogram of product. In products with a high viscosity and/or a very high content of cells (for example pulp), a determination on the basis of a weighed test sample is the usual procedure. Mix cloudy samples well before dilution.Page 4 EN 12133
29、: 1997 BSI 1998 7.2 Test procedure Following the manufacturers instructions for the apparatus used, either titrate to the end potential or plot the potential curve. 7.2.1 Titration to the end potential Pipette 5,0 ml of standard chloride solution (5.4) into a 150 ml beaker. Dilute to approximately 1
30、00 ml with distilled water (5.1) and add 1,0 ml of nitric acid (5.3). Dip the electrode (6.3) into the solution, and add silver nitrate solution (5.5) from the micro-burette (6.4) while stirring slowly using the magnetic stirrer (6.2). Titrate a total of 4,00 ml in steps of 1,00 ml, recording the po
31、tential in millivolts at each step on the pH-millivoltmeter (6.1). Then titrate a further 2,00 ml, in steps of 0,2 ml. Finally, titrate up to a total of 10,00 ml in 1,00 ml steps. After each addition, wait about 30 s before reading the potential in millivolts. Plot the values obtained against the vo
32、lume (in millilitres) of standard solution added. Hence estimate the end potential from the inflection point on the curve. Pipette 5,0 ml of standard chloride solution (5.4) into a 150 ml beaker. Add 95 ml of water (5.1), followed by 1,0 ml of nitric acid (5.3). After inserting the electrode, titrat
33、e the solution to the equivalence potential obtained previously. This estimation should be repeated until a reproducible figure is obtained. This figure then serves for all the chloride estimations in each particular batch of samples. Pipette 50,0 ml of a suitably diluted sample into a 150 ml beaker
34、. Add 50 ml of distilled water followed by 1,0 ml of nitric acid, and titrate as above. 7.2.2 Determination of potential curve For particularly accurate determinations it is possible to obtain the complete titration curve of the test sample against silver nitrate standard solution. The equivalence p
35、oint can then be obtained graphically, or, for the highest accuracy, by calculation. Pipette 50 ml of the suitably diluted sample into a 150 ml beaker with 50 ml of distilled water (5.1) and 1 ml of nitric acid (5.3). Titrate against the silver nitrate standard solution in 0,5 ml steps and record th
36、e corresponding potential at each step. Use this initial titration to give the rough titration volume. Repeat the estimation under the same conditions. Begin in 0,5 ml steps and reduce these to 0,2 ml steps once within 1,5 ml to 2,0 ml of the expected endpoint. Continue similarly after the endpoint
37、and then raise the steps to 0,5 ml in a symmetrical fashion. 8 Calculation 8.1 Calculation for the end potential technique If n ml of silver nitrate solution were used, the chloride content r Cl 2, in milligrams per litre, is calculated from the following equation: r Cl 2 = n 17,72 (1) Take into acc
38、ount any dilution factor and the relationship of the value to mass or volume in the final calculation. If a concentrated product has been diluted to single strength, report the relative density of the single strength sample. Report the chloride content for fruit juice in milligrams per litre to one
39、decimal place, and for vegetable juice in grams per litre to one decimal place. 8.2 Calculation for the potential curve technique The volume of standard solution at the equivalence point is calculated from the following expression: V = V9 +DV i (2) DDE 1 DDE 1 +DDE 2 The chloride content r Cl 2, in
40、milligrams per litre, is calculated from the following expression: r Cl 2 = V 17,72 (3) Take into account any dilution factor and the relationship of the value to mass or volume in the final calculation. If a concentrated product has been diluted to single strength, report the relative density of th
41、e single strength sample. Report the chloride content for fruit juice in milligrams per litre to one decimal place, and for vegetable juice in grams per litre to one decimal place. Table 1. Example c (AgNO 3 )= 0,025 mol/l Potential 1st difference DE 2nd difference DDE ml mV mV mV 0,0 204 4 0,2 208
42、4 0,4 212 6 0,6 218 6 0,8 224 6 1,0 230 8 1,2 238 12 1,4 250 22 1,6 272 44 22 1,8 316 34 10 2,0 350 26 2,2 376 20 2,4 396 In this example, the endpoint of the titration is between 1,6 ml and 1,8 ml, where the largest potential rise takes place (DE = 44 mV). The volumes used for calculation of this p
43、oint are as follows: V = 1,6 + 0,2 = 1,74 ml (4) 22 2 2+1 0Page 5 EN 12133 : 1997 BSI 1998 9 Precision Details of the inter-laboratory test on the precision of the method are summarized in annex B. The values derived from the inter-laboratory test may not be applicable to analyte concentration range
44、s and matrices other than given in annex B. 9.1 Repeatability The absolute difference between two single test 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
45、 cases. The values are: orange juice: r = 1,2 mg/l; tomato juice: r = 0,1 g/l. 9.2 Reproducibility The absolute difference 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
46、: orange juice: R = 6,6 mg/l; tomato juice: R = 0,2 g/l. 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; the date and type of sampli
47、ng procedure (if known); the date of receipt; the date of test; the test results and units in which they have been expressed; whether the repeatability of the method has been verified; any particular points observed in the course of the test; any operations not specified in the method or regarded as
48、 optional, which might have affected the results.Page 6 EN 12133 : 1997 BSI 1998 Annex A (informative) Bibliography Hadorn, H. Chlorhaltige Extraktionsmittel-Ru ckstande in coffeinfreiem Kaffee: 56, 116, 1965. In: Mitt. Gebiete Lebensm. Hyg. Chloride analysis of wines: L272.33. 7677, 1990. In: The O
49、fficial Journal of the European Communities. Determination of chloride content: No. 37, 1991. In: The collected Analyses of the International Federation of Fruit Juice Producers. Loose-leaf edition, as of 1996 - Zug: Swiss Fruit Union. Annex B (informative) Statistical results of the inter-laboratory test In accordance with ISO 5725 : 1986, the following parameters have been defined in an inter-laboratory test. (For literature pertaining to the method see annex A). The test was conducted by the Int
