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1、INTERNATIONAL STANDARD IS0 11214 First edition 1996-07-01 Modified starch - Determination of carboxyl group content of oxidized starch Amidon modifi6 - Dosage des groupes carboxyles dans I amidon oxyd6 Reference number IS0 11214:1996(E) IS0 11214:1996(E) Foreword IS0 (the International Organization
2、for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been established has t
3、he right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft I
4、nternational Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 11214 was prepared by Technical Committee lSO/TC 93,
5、Starch (including derivatives and by-products). Annexes A and B of this International Standard are for information only. 0 IS0 1996 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, includ
6、ing photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case Postale 56 l CH-121 1 Geneve 20 l Swi tzerland Printed in Switzerland INTERNATIONAL STANDARD 0 ISO ISO 11214:1996(E) Modified starch - Determination of carboxyl group
7、 content of oxidized starch 1 Scope This International Standard specifies a method for the determination of the carboxyl group content of oxidized starch. The method is suitable for determining carboxyl group contents up to 1 % (m/m). 2 Normative references The following standards contain provisions
8、 which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possi
9、bility of applying the most re- cent editions of the standards indicated below. Members of IEC and IS0 maintain registers of cur- rently valid International Standards. IS0 1666: -J), Starch - Determination of moisture content - Oven-drying method. I SO 3696: 1987, Water for analytical labora tory us
10、e - Specification and test methods. IS0 3946:1982, Starches and derived products - Determination of total phosphorus content - Spectrophotometric method. 3 Principle The carboxyl groups are converted into the acid form by adding a mineral acid to a homogenized test por- tion of the oxidized starch.
11、The cations and the excess acid are eliminated by washing with water. The washed sample is gelatinized and titrated with sodium hydroxide standard solution. For oxidized potato starch, the result is corrected for the phosphate group content. 4 Reagents and materials Use only reagents of recognized a
12、nalytical grade, un- less otherwise specified, and water complying with grade 2 in accordance with IS0 3696. The water used shall be free of carbon dioxide. 4.1 Hydrochloric acid, 0,l mol/l solution. 4.2 Sodium hydroxide, standard volumetric sol- ution, c(NaOH) = 0,l mol/l, free of carbon dioxide. 4
13、.3 Phenolphthalein in ethanol, 1 g/l solution,- 90 % (VW). 4.4 Silver nitrate, 10 g/l solution. 5 Apparatus Usual laboratory apparatus and in particular the fol- lowing. 5.1 Beakers, of capacity 100 ml and 600 ml. 5.2 Magnetic stirrer. 1) To be published. (Revision of IS0 1666:1973) IS0 11214:1996(E
14、) 0 IS0 5.3 Vacuum filter, equipped with a fritted glass crucible of medium porosity, or a Buchner funnel, of diameter 55 mm, equipped with a small, round filter paper (medium filtration rate). 5.4 Boiling water bath. 5.5 Mechanical stirrer. 5.6 Blade mill. 5.7 Test sieve, of aperture size 800 pm. 6
15、 Preparation of the test sample Pass the sample through the test sieve (5.7). If the sample does not pass through the sieve, grind it using the blade mill (5.6) so that it completely passes through the sieve. Homogenize the sample. NOTE 1 In the case of oxidized maize or wheat starch, it may be desi
16、rable to defat the sample by Soxhlet extraction with a mixture of propanol and water 3 + 1 (V/V) in order to correct for the contribution of lipids to the carboxyl group content. 7 Procedure 7.1 Test portion Weigh, to the nearest 0,l mg, 5 g of the test sample into a 100 ml beaker (5.1). 7.2 Convers
17、ion of the carboxyl salts Add 25 ml of the hydrochloric acid solution (4. I) to the beaker and stir for 30 min on the magnetic stirrer (5.2). 7.3 Washing Filter the suspension under vacuum through a fritted glass crucible or Btichner funnel (see 5.3). Wash the cake obtained with water until the filt
18、rate contains no chloride ions. Test for the absence of chloride ions by adding 1 ml of the silver nitrate solution (4.4) to 5 ml of filtrate. Turbidity or precipitation occurs within 1 min if chloride is present. Washing the cake will take approximately 300 ml of water. 7.4 Gelatinization Quantitat
19、ively transfer the cake obtained into a 600 ml beaker (5.1) with 100 ml of water. Add 200 ml of water, place the beaker in the boiling water bath (5.4) stir continuously with the mechanical stirrer (5.5) until the starch gelatinizes and continue stirring for another 15 min. NOTES 2 Direct heating wi
20、th a hotplate or Bunsen burner may overheat or scorch the material which will lead to higher results. 3 A complete gelatinization makes rapid titration easier and increases the sensitivity of the detection of the end- point. 7.5 Titration Remove the beaker from the boiling bath and titrate while sti
21、ll hot with the sodium hydroxide solution (4.2) using the phenolphthalein solution (4.3) as indi- cator until a persistent pink colour is obtained. NOTE 4 The end-point (at pH = 8,3) may be determined electrometrically. 7.6 Determination of moisture content Determine the moisture content of the test
22、 sample in accordance with IS0 1666. 7.7 Determination of phosphorus content For oxidized potato starch, determine the phosphorus content, wp, in percentage by mass, of the test sample in accordance with IS0 3946. 8 Expression of results 8.1 Calculation Calculate the carboxyl group content, based on
23、 the dry substance, using the equation Wr = cVMcx 100 X 100 L m ” 100-w, where WC c V MC is the total carboxyl group content, in per- centage by mass, based on the dry sub- stance; is the concentration, in moles per litre, of sodium hydroxide solution used for the titration; is the volume, in millil
24、itres, of sodium hy- droxide solution used for the titration; is the relative molecular mass of the carboxyl function (MC = 0,045); 2 -,-,- Q IS0 IS0 11214:1996(E) m is the mass, in grams, of the test portion The probability level is 95 % when the repeatability (7.1); and reproducibility limits are
25、obtained. wm is the mass, moisture content, in percentage by of the test sample. NOTE 5 The lipid content of maize and wheat starch contributes to the value obtained for the carboxyl group content by approximately 0,l % (m/m). In the case of oxidized maize or wheat starch, the total carboxyl group c
26、ontent may be corrected for, if desired, either by deducting 0,l % (m/m) from wc or by determining wc of a test sample which has been defatted by Soxhlet extraction with a mix- ture of propanol and water 3 + 1 (V/V) (see also note I). 8.2 Correction for phosphate groups The phosphate groups attached
27、 to oxidized potato starch contribute to the value obtained for the carboxyl group content. For oxidized potato starch, correct the total carboxyl group content resulting from 8.1 by deducting 3wp from wc. NOTE 6 The correction quantity, 3wP, is derived from the following calculation: where is the p
28、hosphorus content, in percentage by mass, of the test sample, obtained in 7.7; n is the number of free acid groups left on phosphorus (n = 2); is the relative molecular mass of the carboxyl function (MC = 0,045); is the relative molecular mass of phosphorus (Mp = 0,031) . 9 Precision The precision o
29、f the method was established by an interlaboratory test carried out in accordance with IS0 5725-2 (reference 2 in annex B). See annex A for a summary of the statistical results of this test. 9.1 Repeatability The absolute difference between two independent test results, obtained using the same metho
30、d on identical test material in the same laboratory by the same operator using the same equipment within a short interval of time, should not be greater than 6 % of the higher of the two results. 9.2 Reproducibility The absolute difference between two independent test results, obtained using the sam
31、e method on identical test material in different laboratories with different operators using different equipment, should not be greater than 16 % of the higher of the two results. 10 Test report The test report shall specify a) a reference to this International Standard; b) the method used; c) the r
32、esult(s) obtained; d) if the repeatability has been checked, the final quoted result obtained. It shall also mention all operating details not specified in this International Standard, or regarded as optional, together with details of any incidents which may have influenced the test result(s). The t
33、est report shall include all information necessary for the complete identification of the sample. IS0 11214:1996(E) Annex A (informative) Table A.1 - Statistical results of the interlaboratory test Parameter Number of laboratories retained after eliminating outliers Number of outliers (laboratories)
34、 Number of accepted results Mean carboxyl group content % (m/m) Repeatability standard deviation, sr % (m/m) Repeatability relative standard deviation, % Repeatability limit, r = 2,8 x sr % (m/m) Reproducibility standard deviation, SR % (m/m) Reproducibility relative standard deviation, % I) M: modi
35、fied maize starch. P: modified potato starch. 4 -,-,- , 0 IS0 IS0 11214:1996(E) Annex B (informative) Bibliography I IS0 5725-l : 1994, Accuracy (trueness and precision) of measurement methods and results - Part I: General principles and definitions. 2 IS0 5725-2:1994, Accuracy (trueness and precisi
36、on) of measurement methods and results - Part 2: .Basic method for the determination of repeatability and reproducibility of a standard measurement method. -,-,- IS0 11214:1996(E) KS 67.180.20 Descriptors: carbohydrates, starches, chemical anaiysls, determination of content, volumetric analysis. Price based on 5 pages -,-,-