1、 ISO 2017 Iron ores Determination of aluminium Part 1: Flame atomic absorption spectrometric method Minerais de fer Dosage de laluminium Partie 1: Mthode par spectromtrie dabsorption atomique dans la flamme TECHNICAL REPORT ISO/TR 4688-1 Reference number ISO/TR 4688-1:2017(E) First edition 2017-04 I
2、SO/TR 4688-1:2017(E)ii ISO 2017 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2017, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including ph
3、otocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41
4、 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO/TR 4688-1:2017(E)Foreword iv 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Principle 1 5 Reagents 1 6 Apparatus . 2 7 Sampling and samples 3 7.1 Laboratory sample . 3 7.2 Preparation of predried test samples 3
5、8 Procedure. 3 8.1 Number of determinations . 3 8.2 Test portion 4 8.3 Blank test and check test 4 8.4 Determination . 4 8.4.1 Decomposition of the test portion 4 8.4.2 Treatment of the residue 4 8.4.3 Preparation of the test solution 4 8.4.4 Adjustment of the atomic absorption spectrometer. 5 8.4.5
6、 Atomic absorption measurements . 5 9 Expression of results 6 9.1 Calculation of mass fraction of aluminium . 6 9.2 General treatment of results . 6 9.2.1 Repeatability and permissible tolerance 6 9.2.2 Determination of analytical result 7 9.2.3 Between-laboratories precision . 7 9.2.4 Check for tru
7、eness 7 9.2.5 Calculation of final result 8 9.3 Oxide factor 9 10 Test report . 9 Annex A (informative) Flowsheet of the procedure for the acceptance of analytical values for test samples .10 Annex B (informative) Derivation of repeatability and permissible tolerance formulae 11 Annex C (informative
8、) Precision data obtained by international analytical trials .12 Bibliography .13 ISO 2017 All rights reserved iii Contents Page ISO/TR 4688-1:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The wor
9、k 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 committee. International organizations, governmental and non-governme
10、ntal, 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. The procedures used to develop this document and those intended for its further maintenance are described in th
11、e ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives). Attention is drawn to the p
12、ossibility 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. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO lis
13、t of patent declarations received (see www .iso .org/ patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions re
14、lated to conformity assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: w w w . i s o .org/ iso/ foreword .html. This document was prepared by ISO/TC 102, Iron ore and direct reduced
15、iron, Subcommittee SC 2, Chemical analysis. This first edition Technical Report cancels and replaces the second edition (ISO 4688-1:2006), which has been technically revised. It has been converted to a Technical Report as it is no longer suitable for determination of aluminium as a referee method.iv
16、 ISO 2017 All rights reserved TECHNICAL REPORT ISO/TR 4688-1:2017(E) Iron ores Determination of aluminium Part 1: Flame atomic absorption spectrometric method WARNING This document may involve hazardous materials, operations and equipment. This document does not purport to address all of the safety
17、problems associated with its use. It is the responsibility of the user of this document to establish appropriate health and safety practices. 1 Scope This document describes a flame atomic absorption spectrometric method for the determination of the mass fraction of aluminium in iron ores. This meth
18、od is applicable to mass fractions of aluminium between 0,1 % and 5,0 % in natural iron ores, iron ore concentrates and agglomerates, including sinter products. 2 Normative references There are no normative references in this document. 3 T erms a nd definiti ons No terms and definitions are listed i
19、n this document. ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at h t t p :/ www .electropedia .org/ ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp 4 Principle The test portion is decomposed
20、by treatment with hydrochloric acid and a small amount of nitric acid. The mixture is evaporated to dehydrate silica, followed by dilution and filtration. The residue is ignited and silica is removed by evaporation with hydrofluoric and sulfuric acids. The residue is then fused with sodium carbonate
21、 and the cooled melt is dissolved in the filtrate. The solution obtained is aspirated into the flame of an atomic absorption spectrometer using a dinitrogen oxide/acetylene burner. The absorbance values obtained for aluminium are compared with those obtained from the calibration solutions. 5 Reagent
22、s During analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 5.1 Sodium carbonate (Na 2 CO 3 ), anhydrous. ISO 2017 All rights reserved 1 ISO/TR 4688-1:2017(E) 5.2 Hydrochloric acid, 1,19 g/ml. 5.3 Nitric acid, 1,4 g/ml. 5.4 Hydrochloric
23、 acid, 1,19 g/ml, diluted 1 + 9. 5.5 Hy dr ofluoric acid, 1, 13 g/ml, 40 % (mass fraction), or 1,185 g/ml, 48 % (mass fraction). 5.6 Sulfuric acid, 1,84 g/ml, diluted 1 + 1. 5.7 Background solution Dissolve 10 g of high purity iron minimum purity 99,9 % (mass fraction) of mass fraction of aluminium
24、less than 0,002 %, in 50 ml of hydrochloric acid (5.2) and oxidize by adding nitric acid (5.3) drop by drop. Evaporate until a syrupy consistency is obtained. Add 20 ml of hydrochloric acid (5.2) and dilute to 200 ml with water. Dissolve 17 g of sodium carbonate (5.1) in water and add it to the iron
25、 solution. Transfer the solution to a 1 000 ml one-mark volumetric flask and dilute to volume with water. 5.8 Aluminium standard solution, 500 g Al/ml. Dissolve 0,5 000 g of high purity aluminium minimum purity 99,9 % (mass fraction) in 25 ml of hydrochloric acid (5.2). Cool, transfer to a 1 000 ml
26、one-mark volumetric flask, dilute to volume with water and mix. 5.9 Aluminium calibration solutions Transfer 2,0 ml; 5,0 ml; 10,0 ml; 20,0 ml; 40,0 ml; and 50,0 ml portions of aluminium standard solution (5.8) to 200 ml volumetric flasks. Dilute to about 100 ml. Add 6 ml of hydrochloric acid (5.2) a
27、nd 60 ml of background solution (5.7) to each flask. Prepare a zero aluminium calibration solution by transferring 60 ml of the background solution to a 200 ml volumetric flask, and add 6 ml of hydrochloric acid (5.2). Dilute all the solutions to 200 ml with water and mix. (For an atomic absorption
28、spectrometer having high sensitivity, smaller portions of the standard solution may be used.) 6 Apparatus Ordinary laboratory apparatus, including one-mark pipettes and one-mark volumetric flasks complying with the specifications of ISO 648 and ISO 1042, respectively, and the following. 6.1 Platinum
29、 crucible, of capacity 30 ml. 6.2 Muffle furnac e, capable of maintaining a temperature of approximately 1 100 C. 6.3 Atomic absorption spectrometer, equipped with a dinitrogen oxide/acetylene burner. WARNING Follow the manufacturers instructions for igniting and extinguishing the d i n i t r o g e
30、n o x i d e / a c e t y l e n e f l a m e t o a v o i d p o s s i b l e e x p l o s i o n h a z a r d s . W e a r t i n t e d s a f e t y g l a s s e s w h e n e v e r t h e f l a m e i s b u r n i n g . The atomic absorption spectrometer used in this method should meet the following criteria. a) Mi
31、nimum sensitivity: the absorbance of the most concentrated aluminium calibration solution (5.9) should be at least 0,3.2 ISO 2017 All rights reserved ISO/TR 4688-1:2017(E) b) Graph linearity: the slope of the calibration graph covering the top 20 % of the concentration range (expressed as a change i
32、n absorbance) should not be less than 0,7 of the value of the slope for the bottom 20 % of the concentration range determined in the same way. c) Minimum stability: the standard deviation of the absorbance of the most concentrated calibration solution and that of the zero calibration solution, each
33、being calculated from a sufficient number of repetitive measurements, should be less than 1,5 % and 0,5 %, respectively, of the mean value of the absorbance of the most concentrated calibration solution. The use of a strip-chart recorder and/or digital readout device is recommended to evaluate crite
34、ria a), b) and c) and for all subsequent measurements. NOTE Instrument parameters can vary with each instrument. The following parameters were successfully used in several laboratories and they can be used as guidelines. Solutions were aspirated into a dinitrogen oxide/acetylene flame of a premix bu
35、rner. Aluminium hollow cathode lamp, mA 25 Wavelength, nm 396,2 Dinitrogen oxide flow rate, l/min 13,8 Acetylene flow rate, l/min 6,6 In systems where the values shown above for gas flow rates do not apply, the ratio of the gas flow rates may still be a useful guideline. 7 Sampling and samples 7.1 L
36、aboratory sample For analysis, use a laboratory sample of minus 100 m particle size which has been taken and prepared in accordance with ISO 3082. In the case of ores having significant contents of combined water or oxidizable compounds, use a particle size of minus 160 m. NOTE A guideline on signif
37、icant contents of combined water and oxidizable compounds is incorporated in ISO 7764. 7.2 Preparation of predried test samples Thoroughly mix the laboratory sample and, taking multiple increments, extract a test sample in such a way that it is representative of the whole contents of the container.
38、Dry the test sample at 105 C 2 C, as specified in ISO 7764. (This is the predried test sample.) 8 Procedure 8.1 Number of determinations Carry out the analysis at least in duplicate in accordance with Annex A, independently, on one predried test sample. NOTE The expression “independently” means that
39、 the second and any subsequent result is not affected by the previous result(s). For this particular analytical method, this condition implies that the repetition of the procedure is carried out either by the same operator at a different time or by a different operator including, in either case, app
40、ropriate recalibration. ISO 2017 All rights reserved 3 ISO/TR 4688-1:2017(E) 8.2 Test portion Taking several increments, weigh, to the nearest 0,000 2 g, approximately 1 g of the predried test sample obtained in accordance with 7.2. The test portion should be taken and weighed quickly to avoid reabs
41、orption of moisture. 8.3 Blank test and check test In each run, one blank test and one analysis of a certified reference material of the same type of ore should be carried out in parallel with analysis of the ore sample(s) under the same conditions. A predried test sample of the certified reference
42、material should be prepared as specified in 7.2. The certified reference material should be of the same type as the sample to be analysed, and the properties of the two materials should be sufficiently similar to ensure that, in either case, no significant changes in the analytical procedure will be
43、come necessary. Where the analysis is carried out on several samples at the same time, the blank value may be represented by one test, provided that the procedure is the same and that the reagents used are from the same reagent bottles. Where the analysis is carried out on several samples of the sam
44、e type of ore at the same time, the analytical value of one certified reference material may be used. 8.4 Determination 8.4.1 Decomposition of the test portion Transfer the test portion (8.2) to a 250 ml beaker. Moisten with a few millilitres of water, add 25 ml of hydrochloric acid (5.2), cover wit
45、h a watch-glass and heat gently. Increase the heat and digest just below boiling, until no further attack is apparent. Add 2 ml of nitric acid (5.3) and digest for several minutes. Remove the watch-glass and evaporate the solution to dryness. Heat the salts on the hot-plate at 105 C to 110 C for 30
46、min. Add 5 ml of hydrochloric acid (5.2), cover the beaker with a watch-glass, and warm for several minutes. Add 50 ml of water, heat to boiling, wash the watch-glass and the walls of the beaker, and filter the solution through a medium-texture paper into a 250 ml beaker. Carefully remove all adheri
47、ng particles with a rubber-tipped rod or moistened filter paper. Wash three times with hydrochloric acid (5.4), then with hot water until the filter paper is free of iron. Transfer the paper and residue to a platinum crucible (6.1). Evaporate the filtrate to about 100 ml and retain it. 8.4.2 Treatme
48、nt of the residue Ignite the paper and residue in the platinum crucible (6.1) at a low temperature (500 C to 800 C). Cool, moisten with a few drops of water, add 3 or 4 drops of sulfuric acid (5.6) and 10 ml of hydrofluoric acid (5.5), Evaporate slowly to expel silica and then fume to remove the exc
49、ess sulfuric acid. Ignite at about 700 C. Add 1,0 g of sodium carbonate (5.1) to the residue (see Note), cover the crucible, and fuse over a burner or in a muffle furnace (6.2) until a clear melt is obtained (at about 1 100 C for 15 min). NOTE If difficulties are experienced with the fusion, 2 g of sodium carbonate (5.1) can be used, with a doubled volume of hydrochloric acid (5.2). In this case, prepare the background solution (5.7) with doubled quantities of sodium carbonate and hydrochloric acid. 8.4.3 P
