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1、BRITISH STANDARD BS ISO 2171:2007 Cereals, pulses and by-products Determination of ash yield by incineration ICS 67.060 ? Licensed Copy: London South Bank University, London South Bank University, Thu Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI BS ISO 2171:2007 This British Standard w
2、as published under the authority of the Standards Policy and Strategy Committee on 30 November 2007 BSI 2007 ISBN 978 0 580 56428 4 National foreword This British Standard is the UK implementation of ISO 2171:2007. It supersedes BS 4317-10:1993 which is withdrawn. The UK participation in its prepara
3、tion was entrusted to Technical Committee AW/4, Cereals and pulses. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct applic
4、ation. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments issued since publication Amd. No. DateComments Licensed Copy: London South Bank University, London South Bank University, Thu Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI Reference numbe
5、r ISO 2171:2007(E) INTERNATIONAL STANDARD ISO 2171 Fourth edition 2007-11-01 Cereals, pulses and by-products Determination of ash yield by incineration Crales, lgumineuses et produits drivs Dosage du taux de cendres par incinration BS ISO 2171:2007 Licensed Copy: London South Bank University, London
6、 South Bank University, Thu Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI ii Licensed Copy: London South Bank University, London South Bank University, Thu Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI iii Contents Page Foreword iv 1 Scope . 1 2 Normative references. 1 3 Te
7、rms and definitions. 1 4 Principle. 2 5 Reagents 2 6 Apparatus 2 7 Sampling 3 8 Preparation of the test sample 3 9 Procedure 3 9.1 Determination of the moisture content. 3 9.2 Preparation of the ashing dishes 3 9.3 Preparation of the test portion 4 9.4 Pre-ashing . 4 9.5 Ashing 4 9.6 Number of deter
8、minations. 4 10 Expression of results . 4 11 Precision 5 11.1 Interlaboratory tests. 5 11.2 Repeatability 5 11.3 Reproducibility 5 11.4 Critical difference 6 11.5 Uncertainty 6 12 Test report . 6 Annex A (informative) Results of interlaboratory tests 8 Annex B (informative) Practical application of
9、repeatability and reproducibility limits . 10 Bibliography. 11 BS ISO 2171:2007 Licensed Copy: London South Bank University, London South Bank University, Thu Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI iv Foreword ISO (the International Organization for Standardization) is a worldwid
10、e federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that
11、 committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in ac
12、cordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard req
13、uires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 2171 was prepared by Technic
14、al Committee ISO/TC 34, Food products, Subcommittee SC 4, Cereals and pulses. This fourth edition cancels and replaces the third edition (ISO 2171:1993), which has been technically revised. BS ISO 2171:2007 Licensed Copy: London South Bank University, London South Bank University, Thu Dec 20 03:19:3
15、1 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 1 Cereals, pulses and by-products Determination of ash yield by incineration 1 Scope This International Standard specifies a method for determining the ash yielded by cereals, pulses and their milled products intended for human consumption. The source mat
16、erials covered are: a) grains of cereals; b) flours and semolinas; c) milled products (bran and high bran content products, sharps); d) mixed cereal flours (mixes); e) cereal by-products other than milled products; and f) pulses and their by-products. This International Standard is not applicable to
17、 starches and starch derivatives (see ISO 3593), to products intended for animal feeding stuffs (see ISO 5984), or to seeds. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For und
18、ated references, the latest edition of the referenced document (including any amendments) applies. ISO 712, Cereals and cereal products Determination of moisture content Routine reference method ISO 6540, Maize Determination of moisture content (on milled grains and on whole grains) ISO 24557:1), Pu
19、lses Determination of moisture content Air-oven method 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 ash incombustible residue obtained after incineration according to the method given in this International Standard 1) To be published. BS I
20、SO 2171:2007 Licensed Copy: London South Bank University, London South Bank University, Thu Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 2 4 Principle A test portion is incinerated until combustion of organic matter is complete, then the residue obtained is weighed. The residue obtaine
21、d is flaky after incineration at 550 C and vitrified after incineration at 900 C. In general, products containing salts (e.g. sodium chloride, pyrophosphate) shall be incinerated at (550 10) C. Table 1 summarizes incineration temperatures according to product type. Table 1 Incineration temperatures
22、and product type Product type Incineration temperature Flours (550 10) C (900 25) C Semolinas (550 10) C (900 25) C Cereal grains (550 10) C (900 25) C Other milled products (e.g. bran, high bran content products, sharps) (550 10) C Mixed cereal products (mixes) (550 10) C Cereal by-products other t
23、han milled products (550 10) C Pulses and their by-products (550 10) C 5 Reagents Unless stated otherwise, use only reagents of recognized analytical quality and distilled or demineralized water or water of equivalent purity. 5.1 Hydrochloric acid, aqueous solution of one part by volume of HCl (35 %
24、 volume fraction) and one part by volume of water. 5.2 Purified diphosphorus pentoxide (P4O10). 5.3 Ethanol. 6 Apparatus 6.1 Grinding mill, easy to clean and having as little dead space as possible, and ensuring rapid, uniform grinding. 6.2 Ashing dish, of capacity not less than 20 ml, rectangular o
25、r round shape, flat-bottomed and having a surface area of not less than 12 cm2. Suitable materials for the ashing dish which do not deteriorate under test conditions at the temperature of operation are: a) at 900 C platinum or rhodium; b) at 550 C quartz or silica. In both cases, the material used s
26、hall allow compliance with the precision values. The dishes shall be cleaned by complete immersion for at least 1 h in hydrochloric acid (5.1), then rinsed with running water and then with distilled water. BS ISO 2171:2007 Licensed Copy: London South Bank University, London South Bank University, Th
27、u Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 3 After rinsing, the dishes shall be dried in an oven (6.7) at a temperature and for a period sufficient to eliminate water. 6.3 Electrically heated muffle furnace, with adequate ventilation, provided with temperature control system and a
28、refractory coating which is not liable to lose particles at the ashing temperature, and capable of being maintained at (900 25) C or at (550 10) C. 6.4 Vacuum desiccator, equipped with a perforated aluminium or porcelain plate, and diphosphorus pentoxide (5.2) as drying agent. 6.5 Analytical balance
29、, with an accuracy of 0,01 mg. 6.6 Riffle splitter or cone-shaped divider. 6.7 Oven for drying the ashing dishes. 7 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 spe
30、cified in this International Standard. Recommended sampling methods are given in ISO 6644 and ISO 13690. 8 Preparation of the test sample For grains or products containing whole grains, mix and divide the sample in order to obtain a representative quantity compatible with the type of grinding mill (
31、6.1) being used. Grind the sample thus obtained. The other products do not require grinding. 9 Procedure 9.1 Determination of the moisture content Determine beforehand the moisture content of the test sample in accordance with ISO 712 for cereals other than maize or ISO 6540 in the case of maize or
32、ISO 24557 in the case of pulses. Pulses and their derived products should be processed according to ISO 712 with a 90 min drying time and preconditioning if moisture mass fraction is below 7 % or above 13 %. 9.2 Preparation of the ashing dishes For ashing dishes suitable for use at 900 C (6.2), brin
33、g the previously cleaned dishes up to the incineration temperature being employed by putting them in the muffle furnace (6.3) for 5 min, leave them to cool in the desiccator (6.4), then weigh (6.5) them to within 0,1 mg. For ashing dishes suitable for use at 550 C, place the cleaned dishes in an ove
34、n (6.7) for the time required for drying (e.g. 90 min at 130 C). Immediately before use, remove the dishes from the oven and leave them to cool in a desiccator (6.4), then weigh (6.5) them to within 0,1 mg. BS ISO 2171:2007 Licensed Copy: London South Bank University, London South Bank University, T
35、hu Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 4 9.3 Preparation of the test portion From the test sample prepared according to Clause 8 and carefully mixed, rapidly weigh (6.5) to within 0,1 mg a test portion between 3,9 g and 4,1 g in the case of incineration at 900 C and between 4,
36、9 g and 5,1 g in the case of incineration at 550 C. In the case of low density products, the test portion can be between (2 0,1) g and (3 0,1) g. In the ashing dish, prepared and weighed as described in 9.2, spread out the product, without packing it, to form a uniform layer. 9.4 Pre-ashing Place th
37、e ashing dish and its contents at the entrance of the furnace brought up to the ashing temperature. At 900 C, the products burst into flame spontaneously. At 550 C, it is necessary to ignite them with ethanol (5.3). For pre-ashing at 550 C, it is permissible to put the dishes in the cold furnace and
38、 to let the temperature of the furnace rise to the target temperature. 9.5 Ashing Wait until the product has finished burning, then place the dish inside the furnace. Close the furnace door. Continue the ashing until combustion of the entire product, including the carbon particles contained in the r
39、esidue, is complete, namely 1 h minimum at 900 C, and 4 h minimum at 550 C. Once the ashing is completed, remove the dish from the furnace and place it in the desiccator (6.4) to cool. In order to maintain the efficiency of the desiccator, do not stack dishes. Due to the hygroscopic nature of the as
40、h, as soon as the dish has reached ambient temperature (namely 15 min to 20 min for metallic dishes and 60 min to 90 min minimum for quartz or silica dishes), weigh rapidly to within 0,1 mg. For test portions incinerated at 550 C, special precautions shall be taken to avoid flaky residues being swep
41、t away with the influx of air on opening the desiccator. The validity of the results obtained on this sample shall be checked with respect to the laboratorys self- inspection criteria (e.g. control chart). 9.6 Number of determinations Conduct at least two determinations on the same test sample. 10 E
42、xpression of results The ash yield, as a mass fraction on the dry matter basis expressed as a percentage, wa,d, is given by Equation (1): wmm mw = a,d21 0m 100100 () 100 (1) BS ISO 2171:2007 Licensed Copy: London South Bank University, London South Bank University, Thu Dec 20 03:19:31 GMT+00:00 2007
43、, Uncontrolled Copy, (c) BSI 5 where m0 is the mass, in grams, of the test portion (9.3); m1 is the mass, in grams, of the ashing dish (9.2); m2 is the mass, in grams, of the ashing dish (9.2) and the incinerated residue (9.5); wm is the moisture content, as a percentage by mass, of the sample (see
44、9.1). Take as a result the arithmetic mean of the two determinations if the repeatability conditions (see 11.1) are fulfilled. Express the result to the nearest 0,01 % by mass. If needed, the ash yield, as mass fraction on the wet matter basis expressed as a percentage, wa,w, is given by Equation (2
45、): wmm m = a,w21 0 100 () (2) 11 Precision 11.1 Interlaboratory tests The values for repeatability and reproducibility limits and for critical differences were derived from results of interlaboratory tests carried out in accordance with ISO 5725-1, ISO 5725-2, and ISO 5725-6. Details are summarized
46、in Annex A. The values deriving from these interlaboratory tests may not be applicable to content ranges and matrices other than those given. 11.2 Repeatability The absolute difference between two independent single test results, obtained using the same method on identical test material in the same
47、laboratory by the same operator using the same equipment within a short interval of time, will in not more than 5 % of cases be greater than: r = 2,8 ? sr (3) r = 2,8 ? 0,009 = 0,025 for 0,49 % wa,d u 1,00 % (4) r = 2,8 ? 0,012 = 0,034 for 1,00 % wa,d u 2,53 % (5) where sr is the standard deviation
48、of repeatability. 11.3 Reproducibility The absolute difference between two independent single test results, obtained using the same method on identical test material in different laboratories with different operators using different equipment, will in not more than 5 % of cases be greater than: R =
49、2,8 ? sR (6) R = 2,8 ? 0,023 = 0,064 for 0,49 % wa,d u 1,00 % (7) BS ISO 2171:2007 Licensed Copy: London South Bank University, London South Bank University, Thu Dec 20 03:19:31 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 6 R = 2,8 ? 0,027 = 0,076 for 1,00 % wa,d u 2,53 % (8) where sR is the standard deviation of reproducibility. 11.4 Critical difference The critical difference is the difference between two aver