1、BRITISH STANDARD BS EN 1185:1995 Starches and derived products Determination of sulfur dioxide content Acidimetric method The European Standard EN1185:1994 has the status of a BritishStandardBSEN1185:1995 This BritishStandard, having been prepared under the directionof the BSI Standards Board, was p
2、ublished under theauthority of the Standards Board and comes into effect on 15January1995 BSI01-2000 The following BSI references relate to the work on this standard: Committee referenceAW/100 Draft announced in BSI News January1993 ISBN 0 580 22821 5 Cooperating organizations The European Committee
3、 for Standardization (CEN), under whose supervision this European Standard was prepared, comprises the national standards organizations of the following countries: Austria Oesterreichisches Normungsinstitut Belgium Institut belge de normalisation Denmark Dansk Standard Finland Suomen Standardisoimis
4、liito, r.y. France Association franaise de normalisation Germany Deutsches Institut fr Normung e.V. Greece Hellenic Organization for Standardization Iceland Technological Institute of Iceland Ireland National Standards Authority of Ireland Italy Ente Nazionale Italiano di Unificazione Luxembourg Ins
5、pection du Travail et des Mines Netherlands Nederlands Normalisatie-instituut Norway Norges Standardiseringsforbund Portugal Instituto Portugus da Qualidade Spain Asociacin Espaola de Normalizacin y Certificacin Sweden Standardiseringskommissionen i Sverige Switzerland Association suisse de normalis
6、ation UnitedKingdom BritishStandards Institution Amendments issued since publication Amd. No. Date CommentsBSEN1185:1995 BSI 01-2000 i Contents Page Cooperating organizations Inside front cover National foreword ii Foreword 2 1 Scope 3 2 Normative references 3 3 Principle 3 4 Acidimetric method 3 5
7、Test report 5 National annex NA (informative) Cross-reference Inside back cover Figure Diagram of entrainment apparatus 6BSEN1185:1995 ii BSI 01-2000 National foreword This BritishStandard has been prepared under the direction of the BSI Standards Board and is the English Language version of EN1185:
8、1994 Starches and derived products Determination of sulfur dioxide content Acidimetric method published by the European Committee for Standardization (CEN). It was derived by CEN from ISO5379:1983 Starches and derived products Determination of sulfur dioxide content Acidimetric method and nephelomet
9、ric method, published by the International Organization for Standardization (ISO). This BritishStandard has been produced to fulfil BSIs obligation to publish all approved European Standards but, because of the absence of interest in the UK in the subject concerned, there has been no UK participatio
10、n in the preparation of EN1185. Any queries relating to the EN should be directed to BSI quoting the referenceAW/100. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a
11、 British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theEN title page, pages2 to6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may h
12、ave had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN1185 November1994 ICS67.180.20 Descriptors: Carbohydrates, starches, food starch, tests, determination of content, sulfur dioxide English versi
13、on Starches and derived products Determination of sulfur dioxide content Acidimetric method (ISO5379:1983 modified) Amidons, fcules et produits drivs Dtermination de la teneur en dioxyde de soufre Dosage acidimtrique (ISO5379:1983 modifie) Strken und Strkederivate Bestimmung des Schwefeldioxidgehalt
14、es Acidimetrisches Verfahren (ISO5379:1983 modifiziert) This European Standard was approved by CEN on1994-11-10. 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 al
15、teration. 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 exists in three official versions (English, French, German). A version in any other language made by tra
16、nslation 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 bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembo
17、urg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and UnitedKingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1994 Copyright reserved to CEN members Ref.No.EN1185:199
18、4EEN1185:1994 2 BSI 01-2000 Foreword The text of the International Standard ISO5379:1983, prepared by ISO/TC93, Starch (including derivatives and by-products), was submitted to Formal Vote and was approved by CEN as EN1185 with a common modification. This European Standard shall be given the status
19、of a national standard, either by publication of an identical text or by endorsement, at the latest by May1995, and conflicting national standards shall be withdrawn at the latest by May1995. According to the CEN/CENELEC Internal Regulations, the following countries are bound to implement this Europ
20、ean Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, UnitedKingdom. Common modification The nephelometric method has been deleted.EN1185:1994 BSI 01-2000 3 1 Scope and field of appli
21、cation This International Standard specifies two methods an acidimetric method and a nephelometric method for the determination of the sulfur dioxide content of starches and derived products. 2 References ISO1227, Starch, including derivatives and by-products Vocabulary. ISO5725, Precision of test m
22、ethods Determination of repeatability and reproducibility by inter-laboratory tests. 3 Principle Entrainment in a current of nitrogen of the sulfur dioxide extracted from the acidified and heated product, and fixing and oxidation of the sulfur dioxide by bubbling through a dilute solution of neutral
23、 hydrogen peroxide. Titration of the sulfuric acid formed with standard volumetric sodium hydroxide solution or nephelometric determination in the case of low sulfur dioxide contents. 4 Acidimetric method 4.1 Reagents All reagents shall be of recognized analytical quality and sulfate free. The water
24、 shall be distilled water or water of at least equivalent purity, recently boiled. 4.1.1 Nitrogen, oxygen-free. 4.1.2 Hydrogen peroxide, solution containing approximately9 to10g of H 2 O 2per litre. Place150ml of20 volumes hydrogen peroxide solution or30ml of30%(m/m)(110 volumes) hydrogen peroxide s
25、olution in a1000ml one-mark volumetric flask. Dilute to the mark with water. NOTEThis solution should be freshly prepared. 4.1.3 Hydrochloric acid Place150ml of concentrated hydrochloric acid, ( 20 =1,19g/ml) in a1000ml one-mark volumetric flask. Dilute to the mark with water. 4.1.4 Bromophenol blue
26、 indicator solution Dissolve100mg of bromophenol blue , -bis(3,5-dibromo-4-hydroxyphenyl) toluene-2, -sultone in100ml of20%(V/V) ethanol. 4.1.5 Tashiro indicator solution Dissolve30mg of methyl red 2-4-(dimethylamino)phenyl-azo benzoicacid and50mg of methylene blue3,7-bis(dimethylamino)phenothiazin-
27、5-ium chloride in120ml of90%(V/V) ethanol. Dilute to200ml with water, mix and filter. NOTEThe Tashiro indicator(4.1.5) can only be used with the titrimetric method(4.3.4). The bromophenol blue indicator(4.1.4) is appropriate for the titrimetric method and does not hinder the further use of the nephe
28、lometric method (seeclause5). Nevertheless, with this indicator, it is more difficult to detect the end-point. 4.1.6 Sodium hydroxide, standard volumetric solution, c(NaOH)=0,1mol/l 1) ; or 4.1.7 Sodium hydroxide, standard volumetric solution, c(NaOH)=0,01mol/l. 2) In order to obtain a sharp end-poi
29、nt, prepare this solution using carbon dioxide-free water obtained by cooling boiled distilled water under a flow of nitrogen. NOTEThe use of solution(4.1.6) is recommended and a piston-burette is useful for small volumes. If necessary, increase the mass of the test portion. 4.1.8 Iodine, standard v
30、olumetric solution,c(I 2 )=0,01mol/l. 3) 4.1.9 Starch, 5g/l solution. Dissolve0,5g of Lintner starch (see ISO1227) or similar in100ml of water. Heat to boiling while stirring. Add20g of sodium chloride, stir and boil until dissolution is complete. Allow to cool to ambient temperature before use. 4.1
31、.10 Potassium disulfite and ethylenediaminetetraacetic acid (EDTA), disodium salt 4) Dissolve in water0,87g of potassium disulfite (K 2 S 2 O 5 ) and0,20g of disodium dihydrogen ethylenediaminetetraacetate (Na 2 H 2 edta). Transfer the solution quantitatively to a1000ml one-mark volumetric flask. Di
32、lute to the mark with water and mix. 1) Hitherto designated as “0,1N standard volumetric solution”. 2) Hitherto designated as “0,01N standard volumetric solution”. 3) Hitherto designated as “0,02N standard volumetric solution”. 4) This product is intended to protect the sulfite ion from oxidation by
33、 air by complexing traces of copper ion.EN1185:1994 4 BSI 01-2000 4.2 Apparatus Glass apparatus should preferably be fitted with ground glass joints. Ordinary laboratory apparatus, and in particular 4.2.1 One-mark volumetric flasks, of capacity1000ml, complying with the requirements of ISO1042, clas
34、s A. 4.2.2 One-mark pipettes, of capacities0,11235 and20ml, complying with the requirements of ISO648, class A. 4.2.3 Semi-microburette, of capacity10ml, complying with the requirements of ISO385-2, classA. 4.2.4 Burettes, of capacities25 and50ml, complying with the requirements of ISO385-2, class A
35、. 4.2.5 Analytical balance 4.2.6 Magnetic stirrer, efficient, with heating, for use with the flask (A) (see4.2.7.1). 4.2.7 Entrainment apparatus, as shown in theFigure 5)or equivalent equipment for ensuring the displacement and entrainment of sulfur dioxide and its absorption in a solution of hydrog
36、en peroxide. NOTEAvoid making connections with tubes between the condenser and the bubblers as this could lead to absorption of sulfur dioxide. 4.2.7.1 Composition of apparatus A: round-bottom flask, of capacity250ml or greater, with a ground tubulure allowing the introduction of a thermometer. B: v
37、ertical condenser of high efficiency, to fit the flask(A). C: separating funnel, fitted to the flask(A). D: nitrogen inlet with an absorber containing an alkaline solution of pyrogallol. E and E:2 bubblers in series, connected to the condenser(B). F: thermometer. NOTEBetween two determinations, if t
38、he entrainment is sufficiently slow and moderate, only flask (A) need be cleaned. 4.2.7.2 Check tests The apparatus shall satisfy the following requirements: 4.2.7.2.1 Place in the flask (A)100ml of water and proceed as specified in4.3.3. The contents of the bubblers shall remain neutral. 4.2.7.2.2
39、Carry out the following operations: a) Place in the flask (A)100ml of water. Introduce, using a pipette,20ml of the solution(4.1.10). Carry out the entrainment and the determination of sulfur dioxide as specified in4.3.3 and4.3.4. b) Transfer, using a pipette,20ml of the iodine solution(4.1.8),5ml o
40、f the hydrochloric acid(4.1.3) and1ml of the starch solution(4.1.9) into a100ml conical flask(4.1). Titrate, using a burette(4.2.4), with the solution(4.1.10) until the first coloration is discharged. The difference between the sulfur dioxide contents determined ina) andb) shall not exceed1% of thei
41、r arithmetic mean. Operationb) shall not be carried out more than15min after completion of operationa) in order to avoid a possible change in the amount of sulfur dioxide contained in the potassium disulfite/Na 2 H 2 edta solution. 4.3 Procedure 4.3.1 Preparation of test sample Thoroughly mix the la
42、boratory sample. 4.3.2 Test portion Weigh, to the nearest0,01g, a mass of the test sample(see4.3.1) as specified in the following table. This quantity may be increased, in particular in the case of D-glucose. If the expected content is greater than200mg/kg, reduce the test portion accordingly so tha
43、t it does not contain more than10mg of sulfur dioxide and transfer it quantitatively to the flask (A). In the case of certain derived products, the mass of the test portion can be determined by difference by weighing of the container. Add100ml of water to the test portion 6)and mix well by shaking.
44、5) Apparatus of the Lieb and Zaccherl type. Expected sulfur dioxide content mg/kg Approximate mass of test portion g 50 50 to200 100 50 6) In the case of a test portion of more than100g (for example D-glucose), the quantity of water added should be equal to that of the test portion.EN1185:1994 BSI 0
45、1-2000 5 4.3.3 Entrainment 4.3.3.1 Place in the funnel (C)50ml of the hydrochloric acid(4.1.3). 4.3.3.2 In each of the bubblers (E and E), place, by means of a pipette,3ml of the hydrogen peroxide solution(4.1.2), 0,1ml of the bromophenol blue indicator solution(4.1.4) (see the note to4.1.5) and neu
46、tralize the hydrogen peroxide solution with the sodium hydroxide solution(4.1.7). 4.3.3.3 Connect the condenser (B) and the bubblers (E and E) to the apparatus, and slowly pass a current of nitrogen to expel the air from the whole equipment. Start the flow of water to the condenser. 4.3.3.4 Allow th
47、e hydrochloric acid contained in the funnel (C) to flow into the flask (A) (if necessary interrupt the flow of nitrogen for a moment). 4.3.3.5 Bring the mixture to boiling point in30min. Boil for30min, while passing a current of nitrogen and stirring with the stirrer(4.2.6). 4.3.4 Titration Add quan
48、titatively the content of the second bubbler to the content of the first bubbler, and titrate the sulfuric acid formed with the sodium hydroxide solution(4.1.6 or4.1.7) depending on the expected sulfur dioxide content. NOTEIf the end point is not sharp, owing to the presence of volatile organic acid
49、s, boil for2min and cool to room temperature before titrating. 4.3.5 Check If the volume V is less than5ml when the0,01mol/l sodium hydroxide solution is used, or less than0,5ml when the0,1mol/l sodium hydroxide solution is used, carry out the determination by the nephelometric method (seeclause5). 4.3.6 Number of determinations Carry out two determinations on the same test sample(4.3.1). 4.4 Expression of results 4.4.1 Method of calculation and formulae If determination by the nephelometric method is no
