1、BRITISH STANDARD BS EN ISO 11212-2:1997 Starch and derived products Heavy metals content Part 2: Determination of mercury content by atomic absorption spectrometry The European Standard EN ISO 11212-2:1997 has the status of a British Standard ICS 67.180.20BSEN ISO 11212-2:1997 This British Standard,
2、 having been prepared under the directionof the Consumer Products and Services Sector Board, was published under theauthority of the Standards Board and comes into effect on 15 May 1997 BSI 02-1999 ISBN 0 580 27457 8 National foreword This British Standard is the English language version of ENISO112
3、12-2:1997. It is identical with ISO11212-2:1997 and implements it as the UK national standard. This British Standard has been produced to fulfil BSIs obligation to implement all European Standards but, because of the absence of interest in the UK in the subject concerned, there has been no UK partic
4、ipation in the preparation of ENISO11212-2. Any queries relating to the EN should be directed to BSI, quoting the reference AW/100. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue u
5、nder the section entitled “International Standards Correspondence Index”, or using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct ap
6、plication. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, theEN ISO title page, page 2, the ISO title page, page ii, pages 1 to 4 and aback cover. This standa
7、rd 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. Amendments issued since publication Amd. No. Date CommentsBSENISO11212-2:1997 BSI 02-1999 i Contents Page National foreword Inside front cover F
8、oreword 2 Foreword ii Text of ISO 11212-2 1ii blankEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 11212-2 March 1997 ICS 67.180 Descriptors: See ISO document English version Starch and derived products Heavy metals content Part 2: Determination of mercury content by atomic absorption spect
9、rometry (ISO 11212-2:1997) Amidons, fcules et produits drivs Teneur en mtaux lourds Partie 2: Dtermination de la teneur en mercure par spectromtrie dabsorption atomique (ISO 11212-2:1997) Strke und Strkederivate Schwermetallgehalt Teil 2: Bestimmung des Quecksilbergehaltes durch Atomabsorptionsspekt
10、rometrie (ISO 11212-2:1997) This European Standard was approved by CEN on 1997-02-28. 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 alteration. Up-to-date lists
11、and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. The European Standards exist in three official versions (English, French, German). A version in any other language made by translation under the responsib
12、ility 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, Luxembourg, Netherlands, Norway, Po
13、rtugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr 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
14、 for CEN national Members. Ref. No. EN ISO 11212-2:1997 EENISO11212-2:1997 BSI 02-1999 2 Foreword The text of the International Standard ISO 11212-2:1997 has been prepared by Technical Committee ISO/TC93 “Starch (including derivatives and by-products)” in collaboration with CEN/CS. This European Sta
15、ndard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September1997, and conflicting national standards shall be withdrawn at the latest by September1997. According to the CEN/CENELEC Internal Regulations, the national
16、standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The
17、 text of the International Standard ISO11212-2:1997 was approved by CEN as a European Standard without any modification. Contents Page Foreword 2 1 Scope 1 2 Definition 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 2 7 Expression of results 3 8 Precision 3 9 Test report 3 Annex A (normative
18、) Result of interlaboratory test 4 Figure 1 Digestion apparatus 2 Table A.1 Interlaboratory test on corn starch 4EN ISO11212-2:1997 ii BSI 02-1999 Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of
19、 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 committee. International organizations, governmental and non-governmental
20、, 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. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. P
21、ublication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 11212-2 was prepared by Technical Committee ISO/TC 93, Starch (including derivatives and by-products). ISO 11212 consists of the following parts, under the gener
22、al title Starch and derived products Heavy metals content. Part 1: Determination of arsenic content by atomic absorption spectrometry; Part 2: Determination of mercury content by atomic absorption spectrometry; Part 3: Determination of lead content by atomic absorption spectrometry with electrotherm
23、al atomization; Part 4: Determination of cadmium content by atomic absorption spectrometry with electrothermal atomization. Annex A of this part of ISO 11212 is for information only. Descriptors: Starches, food starch, chemical analysis, determination of content, heavy metals, mercury, atomic absorp
24、tion spectrometric method.ENISO11212-2:1997 BSI 02-1999 1 1 Scope This part of ISO 11212 specifies a method for the determination of the mercury content of starch, including derivatives and by-products, by atomic absorption spectrometry with cold-vapour generation. The cold-vapour generators current
25、ly available use very different techniques; it is thus impossible to propose a comprehensive method likely to ensure the attainment of satisfactory results on all types of apparatus. Each analyst should therefore optimize the conditions of use of his/her own apparatus on the basis of general or part
26、icular instructions. 2 Definition For the purposes of this part of ISO 11212, the following definition applies. 2.1 mercury content quantity of mercury determined in accordance with the conditions specified in this method and expressed as mercury (Hg), in micrograms per kilogram of the product as re
27、ceived 3 Principle Wet digestion of the organic matrix. Reduction of mercury (Hg 2+ ) to metallic mercury by hydrogen resulting from the action of sodium borohydride (ortin(II) chloride) on hydrochloric acid. Entrainment of the mercury vapour by a flow of gas and determination of monoatomic mercury
28、vapour by atomic absorption spectrometry in a quartz cell. Measurement of the absorbance at a wavelength of253,7nm. Determination of the concentration of mercury in the sample by means of a calibration curve. 4 Reagents Use only reagents of recognized analytical grade and distilled water or water of
29、 equivalent purity. 4.1 Nitric acid (r 20= 1,38 g/ml). 4.2 Hydrogen peroxide, 30% (V/V) solution. 4.3 Sodium borohydride solution Prepare a solution at the concentration recommended in the instructions for use of the cold-vapour generator (5.3). 4.4 Tin(II) chloride solution Prepare a solution at th
30、e concentration recommended in the instructions for use of the cold-vapour generator (5.3). 4.5 Hydrochloric acid solution Prepare a solution at the concentration recommended in the instructions for use of the cold-vapour generator (5.3). 4.6 Mercury standard solution, 1 g/l. Standard solutions are
31、commercially available at this concentration. These solutions may be prepared by weighing and dissolving the salt or metal of known purity. 4.7 Calibration solutions Before each series of measurements, prepare from the standard mercury solution (4.6) at least five calibration solutions covering the
32、range of concentrations to be determined. 100 ml of each calibration solution shall contain 7,5 ml of nitric acid (4.1). 5 Apparatus All the glassware used shall be previously washed by means of suitable products (such as nitric acid) and rinsed with distilled water to eliminate any trace of mercury
33、. Use ordinary laboratory apparatus and, in particular, the following. 5.1 Digestion apparatus (see Figure 1), made of borosilicate glass and consisting of three elements terminating with conical ground joints(5.1.1 to5.1.3). 5.1.1 Soxhlet extraction tube, of capacity 200 ml, equipped with a stopcoc
34、k and a lateral tube connected directly to the flask (5.1.3). 5.1.2 Cooling apparatus, 35 cm long, connected to the top of the Soxhlet extraction tube (5.1.1). 5.1.3 Round-bottom flask, of capacity 250 ml, connected to the lower part of Soxhlet extraction tube (5.1.1). When the stopcock is open, the
35、 device is under reflux; when it is closed the Soxhlet extraction tube(5.1.1) retains the condensed water and acid vapours. 5.2 Atomic absorption spectrometer, consisting of five elements (5.2.1 to 5.2.5). 5.2.1 High-resolution monochromator, allowing a0,2nm bandwidth slit. 5.2.2 Correcting device f
36、or non-specific absorption. 5.2.3 Measuring and photoelectric reception device, with a response time not exceeding about 10 ms. 5.2.4 Detector and signal processing system, allowing recording of the maximum and/or integrated absorbance signal. 5.2.5 Mercury discharge lamp or mercury hollow cathode l
37、amp.ENISO 11212-2:1997 2 BSI 02-1999 5.3 Generator of cold mercury vapour, allowing the generation of cold mercury vapour as well as its transport to a measuring cell whose wavelength is adapted to the spectrometer, and equipped with an automatic sampling device which is necessary to obtain good rep
38、eatability and to reduce the risk of contamination. 5.4 Pipettes and micropipettes, of suitable capacity. 5.5 Analytical balance. 6 Procedure WARNING Mercury is highly toxic and is a very volatile element. It is thus necessary to verify the tightness of the ground joints and of the tap and to avoid
39、any overheating at digestion in order to prevent any loss of mercury vapour. 6.1 Preparation of test sample Thoroughly homogenize the sample. 6.2 Digestion Use the digestion apparatus described in 5.1. Weigh, to the nearest 1mg, about 5g of the test sample into the flask (5.1.3). Add 27,5ml of nitri
40、c acid (4.1) and 1ml of hydrogen peroxide (4.2). Distil under reflux for 4 h leaving the stopcock open. Turn the stopcock off, continue heating and distil until about 20ml 1ml of liquid are recovered in the extraction tube (5.1.1). Stop heating and allow the flask to cool. Separate the flask from th
41、e extraction tube. Add 20ml of water to the digested residue in the flask, bring to the boil for a few minutes, stop heating and allow to cool. Transfer the solution to a100ml volumetric flask, dilute to the mark with distilled water and stir. NOTETo reach the required precision, the tin(II) chlorid
42、e or the gold amalgam enrichment technique can be used as reducing agent. 6.3 Blank test Perform digestion under the same conditions as in6.2, replacing the test portion by 5ml of water. 6.4 Determination of the calibration curve Carry out the analysis of the diluted calibration solutions (4.7) with
43、 reference to the instructions for use of the cold-vapour generator (5.3) by adding the recommended quantities of tin(II) chloride solution(4.4) and sodium borohydride solution(4.3). Measure the absorbance of each calibration solution at a wavelength of 253,7 nm using the spectrometer (5.2). Draw th
44、e calibration curve by plotting the mercury concentrations of the calibrations solutions, expressed in micrograms per litre, as the abscissa against the corresponding values of the signal, read either in maximum absorbance or in integrated absorbance, as the ordinate. The calibration curve shall be
45、periodically checked depending on the length of the series of analyses. 6.5 Determination Measure the absorbance of the test samples under the same conditions as the calibration solutions and compare the results with the previously plotted calibration curve. Figure 1 Digestion apparatusENISO 11212-2
46、:1997 BSI 02-1999 3 7 Expression of results With reference to the calibration curve, determine the concentrations corresponding to the signals of the test portion and the blank. The mercury concentration of the sample, w, expressed in micrograms per kilogram of the product as received, is given by t
47、he equation: where NOTEWhen strictly following this method, the quantification limit can reach 20 g/kg. 8 Precision Details of an interlaboratory test on the precision of the method are summarized in Annex A. The values derived from the interlaboratory test may not be applicable to analyte concentra
48、tion ranges and matrices other than those given in Annex A. 8.1 Repeatability The absolute difference between two independent single test results, obtained using the same method on identical test material in the same laboratory by the same operator using the same equipment within a short interval of
49、 time, will not exceed the repeatability limit r deduced from Table A.1 in more than 5% of cases. 8.2 Reproducibility The absolute difference between two single test results, obtained using the same method on identical test material in different laboratories with different operators using different equipment, will not exceed the reproducibility limit R deduced from Table A.1 in more than 5% of cases. 9 Test report The test report shall specify: the method in accordance with which sampling was carried out, if known; the
