1、BRITISH STANDARD BSENISO 3946:1994 Starches and derived products Determination of total phosphorous content Spectrometric method The European Standard EN ISO3946:1994 has the status of a BritishStandard UDC 664.2:543.847BSENISO3946:1994 This BritishStandard, having been published under the authority
2、 of the Standards Boardand comes into effect on 15December1994 BSI01-2000 The following BSI reference relates to the work on this standard: Draft announced in BSI News March1993 ISBN 0 580 23177 1 Cooperating organizations The European Committee for Standardization (CEN), under whose supervision thi
3、s 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 Standardisoimisliito, r.y. France Association franaise de normalisatio
4、n 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 Inspection du Travail et des Mines Netherlands Nederlands
5、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 normalisation United Kingdom BritishStandards Institution Amend
6、ments issued since publication Amd. No. Date CommentsBSENISO3946:1994 BSI 01-2000 i Contents Page Cooperating organizations Inside front cover National foreword ii Foreword 2 1 Scope and field of application 3 2 Definition 3 3 Principle 3 4 Reagents 3 5 Apparatus 3 6 Procedure 3 7 Expression of resu
7、lts 4 8 Test report 5 Table 5BSENISO3946:1994 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 EN ISO3946:1994 Starches and derived products Determination of total phosphorus content Spectrop
8、hotometric method, published by the European Committee for Standardization (CEN). It is identical with ISO3946:1982 Starches and derived products Determination of total phosphorus content Spectrophotometric method, published by the International organization for Standardization (ISO). This BritishSt
9、andard 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 participation in the preparation of EN ISO3946. Any queries relating to the EN should be directed to BSI. A B
10、ritish 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 British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a f
11、ront cover, an inside front cover, pagesi andii, theENISO title page, pages2 to5 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 the inside front cover.EUROPEAN STANDARD NORME EUROPENNE E
12、UROPISCHE NORM EN ISO3946 August1994 UDC 664.2:543.847 Descriptors: Starches, chemical analysis, determination of content, phosphorus, spectrophotometric analysis English version Starches and derived products Determination of total phosphorus contentSpectrophotometric method (ISO3946:1982) Amidons,
13、fcules et produits drivs Dtermination de la teneur en phosphore total Mthode spectrophotomtrique (ISO3946:1982) Strke und Strkederivate Bestimmung des Gesamtphosphorgehaltes Spektralphotometrisches Verfahren (ISO3946:1982) This European Standard was approved by CEN on1994-08-22. CEN members are boun
14、d 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 obtained on application to the Ce
15、ntral 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 translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status a
16、s the official versions. 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 Comit E
17、uropen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1994 Copyright reserved to CEN members Ref.No.ENISO3946:1994EENISO3946:1994 BSI 01-2000 2 Foreword The text of the International Standard ISO3946:1982, prepared by ISO/TC93, Starch, was su
18、bmitted to formal vote and was approved by CEN as EN ISO3946:1994 on1994-08-22 without any modifications. 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 February1995, and conflicting national sta
19、ndards shall be withdrawn at the latest by February1995. According to the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Po
20、rtugal, Spain, Sweden, Switzerland and United Kingdom.ENISO3946:1994 BSI 01-2000 3 1 Scope and field of application This International Standard specifies a spectrophotometric method for the determination of the total phosphorus content of starch, including derivatives and by-products, in which the e
21、xpected content, calculated as phosphorus (P), does not exceed5% (m/m). 2 Definition total phosphorus content the quantity of phosphorus determined in accordance with the conditions specified in this International Standard and expressed as phosphorus (P) as a percentage by mass of the product as rec
22、eived 3 Principle Destruction of the organic substances by digestion with a sulpho-nitric mixture and conversion of phosphates to orthophosphates. Formation, by means of a reducing agent, of a phosphomolybdate know as molybdenum blue. Spectrophotometric measurement of the intensity of the blue colou
23、r at a wavelength of825nm. 4 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled water of at least equivalent purity. 4.1 Sulpho-nitric reagent Prepared by mixing1 part by volume of sulphuric acid, 20 1,84g/ml,96% (m/m) solution, and1 part by volume of
24、nitric acid, 20 1,38g/ml,65% (m/m) solution. 4.2 Nitric acid, 20 1,38g/ml,65% (m/m) solution. 4.3 Ascorbic acid,50g/l solution. Keep this solution in a refrigerator for a maximum of48h. 4.4 Ammonium molybdate solution, prepared as follows. In a1 l flask, dissolve10,6g of ammonium molybdate tetrahydr
25、ate (NH 4 ) 6 Mo 7 O 24 .4H 2 O in500ml of water. Add500ml of10mol/l sulphuric acid solution, mix and allow to cool to ambient temperature. 4.5 Sodium hydroxide,10mol/l solution. 4.6 Phosphorus, standard solutions. 4.6.1 Stock solution, corresponding to100mg ofPper litre. Weigh, to the nearest0,5mg,
26、0,4393g of anhydrous potassium dihydrogenorthophosphate and dissolve in water. Transfer quantitatively into a1000ml one-mark volumetric flask. Dilute to the mark with water and mix. 1ml of this standard solution contains1004g of P. NOTEThe potassium dihydrogenorthophosphate shall be dried before use
27、 for1h, in a drying oven controlled at105 2 C, and then allowed to cool in a desiccator. 4.6.2 Standard solution, corresponding to4mg of Pper litre. Using a pipette, take10ml of the stock solution(4.6.1) and place it in a250ml one-mark volumetric flask. Dilute to the mark with water and mix. 1ml of
28、this standard solution contains44g of P. 5 Apparatus NOTEEnsure that the detergents used for cleaning glassware do not contain phosphorus. Ordinary laboratory apparatus, and in particular 5.1 One-mark volumetric flasks, of capacities50100200250 and500ml, complying with the requirements of ISO1042. 5
29、.2 Conical flasks, of capacity50ml. 5.3 Digestion flasks, of capacity100ml. 5.4 Pipettes, of capacities1251015 and25ml, complying with the requirements of ISO648. 5.5 Circulation-type cooling bath, of temperature between15 and25 C. 5.6 Boiling water bath 5.7 Hot-plate 5.8 Desiccator, containing an e
30、ffective desiccant. 5.9 Spectrophotometer, fitted with cells of optical path length1,0cm, capable of measuring at a wavelength of825nm. 5.10 Analytical balance 6 Procedure Carry out the preparation of the calibration curve and the determination within2h. 6.1 Preparation of the calibration graph Take
31、 a series of seven50ml conical flasks(5.2). Using a pipette(5.4), introduce into six of them1,02,03,04,05,0 and10,0ml of the standard phosphorus solution(4.6.2), corresponding to48121620 and404g of P. Add water to each of the seven flasks so that the total volume is approximately30ml. Mix.ENISO3946:
32、1994 4 BSI 01-2000 Using a pipette, add to each of the flasks, in the following order,4ml of the ammonium molybdate solution(4.4) and2ml of the ascorbic acid solution(4.3). Mix after each addition. Place the seven flasks in the boiling water bath(5.6) for10min. Cool to ambient temperature by immersi
33、ng the flasks in the cooling bath(5.5). Transfer the contents of the flasks quantitatively to the50ml one-mark volumetric flasks(5.1). Dilute to the marks with water and mix. Using the spectrophotometer(5.9), determine the absorbance at825nm of each of the six solutions, using the solution from the
34、flask without the standard solution as the reference. Plot the calibration curve giving the number of micrograms of phosphorus as a function of the absorbance. 6.2 Preparation of the test sample Mix the sample thoroughly. 6.3 Test portion Weigh, to the nearest0,2mg,0,5g of the test sample(6.2). This
35、 mass corresponds to an absorbance range between0,1 and0,7; if this is notthe case, adjust the test portion accordingly (seethe Table). 6.4 Digestion Transfer the test portion(6.3) into a digestion flask(5.3). Add15ml of the sulpho-nitric mixture(4.1) and mix well. Place the flask on the hot-plate(5
36、.7). Heat gradually until the liquid is boiling gently in the flask. Continue boiling until the brown vapour is replaced by white vapour and the liquid has become clear. A persistent dark colour can be eliminated by adding the nitric acid solution(4.2), drop by drop, whilst continuing the digestion.
37、 Allow to cool, then add10ml of water and eliminate the excess nitric acid solution by heating until the flask is again filled with white vapour. 6.5 Preparation of the test solution Cool the mixture(6.4) again and add45ml of water. Raise the pH to7 with the sodium hydroxide solution(4.5). Transfer
38、the contents of the digestion flask to a one-mark volumetric flask of suitable volume(5.1). Dilute to the mark with water. Mix thoroughly. 6.6 Determination Take an aliquot portion (see the Table) and introduce it into a50ml conical flask. Using a pipette, add, in the following order,4ml of the ammo
39、nium molybdate solution(4.4) and2ml of the ascorbic acid solution(4.3). Mix after each addition. Place the flask in the boiling water bath(5.6) for10min. Cool to ambient temperature by immersing the flask in the cooling bath(5.5). Transfer quantitatively to a50ml one-mark volumetric flask(5.1). Dilu
40、te to the mark with water and mix. Using the spectrophotometer, determine the absorbance at825nm of this solution. Read from the calibration curve (see6.1) the corresponding number of micrograms of phosphorus. 6.7 Blank test Carry out a blank test in parallel with the determination, replacing the te
41、st portion by water. 6.8 Number of determinations Carry out two determinations on the same test sample(6.2). 7 Expression of results 7.1 Method of calculation and formula The total phosphorus (P) content, expressed as a percentage by mass, is given by the formula where m 0 is the mass, in grams, of
42、the test portion(6.3); m 1 is the phosphorus content, in micrograms, of the test solution read from the calibration curve(6.1); V 0 is the dilution volume, in millilitres, of the test solution(6.5); V 1 is the volume, in millilitres, of the aliquot portion used for the determination(6.6). Take as th
43、e result the arithmetic mean of the values obtained in the two determinations provided that the conditions of repeatability(7.2) are satisfied. If not, repeat the test. 7.2 Repeatability The difference between the values obtained in two determinations carried out simultaneously by the same analyst o
44、n the same test sample(6.2), shall not exceed 2% of their arithmetic mean in the case of phosphorus contents greater than0,2% (m/m); 0,004g of phosphorus per100g of product in cases of phosphorus contents less than0,2%(m/m). m 1 V 0 100 m 0 V 1 10 6 -ENISO3946:1994 BSI 01-2000 5 8 Test report The te
45、st report shall indicate the method used and the results obtained. In addition, it shall mention any operating conditions not specified in this International Standard, or regarded as optional, as well as any circumstances that may have affected the results. The test report shall include all details
46、required for the complete identification of the sample. Table Expected phosphorus content % (m/m) Mass of test portion (see6.3) g Dilution volume (see6.5) ml Volume of the aliquot portion (see6.6) ml 0,05 0,05 to0,10 0,10 to0,25 0,25 to0,50 0,50 to1,00 1,00 to2,00 2,00 to5,00 0,500 0,500 0,500 0,500
47、 0,250 0,125 0,125 100 100 100 200 250 250 500 25 10 2 2 2 2 2BSENISO 3946:1994 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the internati
48、onal level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We woul
49、d be grateful if anyone finding an inaccuracy or ambiguity while using this BritishStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standard
