# BS ISO 12744-2006

BRITISH STANDARD BS ISO 12744:2006 Copper, lead, zinc and nickel concentrates — Experimental methods for checking the precision of sampling ICS 73.060.99 BS ISO 12744:2006 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 May 2006 © BSI 2006 ISBN 0 580 48420 3 National foreword This British Standard reproduces verbatim ISO 12744:2006 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee NFE/36, Copper, lead and zinc ores and concentrates, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. — aid enquirers to understand the text; — present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed; — monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 15 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments Reference number ISO 12744:2006(E)INTERNATIONAL STANDARD ISO 12744 Second edition 2006-04-15 Copper, lead, zinc and nickel concentrates — Experimental methods for checking the precision of sampling Concentrés de cuivre, de plomb, de zinc et de nickel — Méthodes expérimentales de contrôle de la fidélité de l échantillonnage BS ISO 12744:2006ii iii Contents Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 General conditions . 1 3.1 General. 1 3.2 Number of lots. 1 3.3 Number of increments and number of samples 1 3.4 Sample processing and analysis 2 3.5 Frequency of precision checks . 2 4 Symbols . 2 5 Method of experiment. 3 5.1 Interleaved samples 3 5.2 Sample processing and analysis 3 5.2.1 Sample processing method 1 (see Figure 2) 3 5.2.2 Sample processing method 2 (see Figure 3) 3 5.2.3 Sample processing method 3 (see Figure 4) 3 6 Evaluation of experimental data 6 6.1 General. 6 6.2 Sample processing method 1 6 6.3 Sample processing method 2 8 6.4 Sample processing method 3 9 7 Assessment of results and action 11 7.1 Primary sampling 11 7.2 Sample processing. 11 7.3 Analysis . 11 8 Recording of data . 11 Annex A (informative) Recording of sampling data 12 Bibliography . 15 BS ISO 12744:2006iv Foreword ISO (the International Organization for Standardization) is a worldwide 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 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 accordance 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 requires 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 12744 was prepared by Technical Committee ISO/TC 183, Copper, lead, zinc and nickel ores and concentrates. This second edition cancels and replaces the first edition (ISO 12744:1997), which has been technically revised. It has been updated to make it consistent with revisions of related International Standards. BS ISO 12744:2006 1 Copper, lead, zinc and nickel concentrates — Experimental methods for checking the precision of sampling WARNING — This International Standard may involve hazardous materials, operations and equipment. It is the responsibility of the user of this International Standard to establish appropriate health and safety practices and determine the applicability of regulatory limitations prior to use. 1 Scope This International Standard specifies methods for checking the precision of primary sampling, sample processing, chemical analysis, physical testing and determination of moisture content of copper, lead, zinc and nickel concentrates being carried out in accordance with the methods specified in ISO 12743, expressed in terms of standard deviations. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 12743, Copper, lead, zinc and nickel concentrates — Sampling procedures for determination of metal and moisture content 3 General conditions 3.1 General The determination of precision of primary sampling is based on collecting pairs of interleaved samples from each lot. If sample processing and measurement are also carried out in duplicate, it is possible to determine the precision of sample processing and analysis. 3.2 Number of lots It is recommended that pairs of interleaved samples be collected from more than 20 lots of the same type of concentrate, in order to reach a reliable conclusion. The lot size shall be chosen to ensure that this requirement is met. 3.3 Number of increments and number of samples The minimum number of increments for checking precision should preferably be twice the number determined in accordance with ISO 12743. Hence, if the number of increments required for routine sampling is n and one lot sample is constituted, the minimum number of increments should be 2n, and two interleaved samples shall be constituted. Alternatively, if the precision is being checked as part of routine sampling, n increments may be taken and two interleaved samples constituted, each comprising n/2 increments. The sampling precision thus obtained must be divided by 2 to obtain the sampling precision for lot samples comprising n increments. BS ISO 12744:20062 3.4 Sample processing and analysis Sample processing shall be carried out in accordance with ISO 12743. The analysis of samples shall be carried out according to the methods specified in the relevant International Standards. 3.5 Frequency of precision checks It is recommended that, even after a precision check has been conducted, further checks be carried out at regular intervals. Precision checks should also be carried out when there is a change in equipment. Because of the large amount of work involved in checking precision, it is recommended that checks be carried out as a part of routine sampling and analysis. 4 Symbols Symbol Definition k Number of lots n Number of increments R 1Absolute difference between duplicates for interleaved samples A and B 1 R Mean absolute difference between duplicates for interleaved samples A and B, for k lots R 2Absolute difference between means for divided interleaved samples A 1and A 2 , and B 1and B 22 R Mean absolute difference between means for divided interleaved samples A 1and A 2 , and B 1and B 2 , for k lots R 3Absolute difference between means for interleaved sample A and interleaved sample B 3 R Mean absolute difference between means for interleaved sample A and interleaved sample B, for k lots s Estimated value of standard deviation, σ 2 1 s Estimated variance from 1 R 2 2 s Estimated variance from 2 R 2 3 s Estimated variance from 3 R s AEstimated standard deviation of analysis s PEstimated standard deviation of sample processing S 1 s Estimated standard deviation of primary sampling SP s Estimated standard deviation of primary sampling and sample processing s TEstimated total standard deviation of primary sampling, sample processing and analysis x i1First duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample A or B x i2Second duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample A or B x ij1First duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample A or B, and j = 1 or 2 and indicates laboratory samples A 1or A 2 , and B 1or B 2x ij2Second duplicate result for sample, where i = 1 and 2 and indicates interleaved sample A or B, and j = 1 or 2 and indicates laboratory samples A 1or A 2 , and B 1or B 2x Mean value of duplicate results x Mean of mean value of duplicate results x Mean of x values, and grand mean for sample processing method 3 x Grand mean of all results for sample processing methods 1 and 2 BS ISO 12744:2006 3 5 Method of experiment 5.1 Interleaved samples Each alternate primary increment shall be diverted so that pairs of interleaved samples A and B are formed. The number of divided increments per primary increment should be the same as for routine sampling. An example of a sampling plan for producing pairs of interleaved samples A and B is shown in Figure 1. 5.2 Sample processing and analysis The pairs of interleaved samples A and B taken in accordance with 5.1 shall be divided separately and subjected to method 1, method 2 or method 3 sample processing and analysis as described in 5.2.1, 5.2.2 or 5.2.3. 5.2.1 Sample processing method 1 (see Figure 2) The two interleaved samples A and B shall be divided separately to prepare four laboratory samples, A 1 , A 2 , and B 1 , B 2 . These laboratory samples shall each be analysed in duplicate, and the duplicates designated x 111and x 112for sample A 1 , x 121and x 122for sample A 2 , x 211and x 212for sample B 1 , and x 221and x 222for sample B 2 . The eight determinations shall be run in random order, by the same analyst on the same day using the same analytical equipment. An example is given in Annex A. NOTE By using method 1, the estimated precisions of primary sampling, sample processing and analysis can be obtained separately. 5.2.2 Sample processing method 2 (see Figure 3) Sample A shall be divided to prepare two laboratory samples, A 1and A 2 . From sample B, only one laboratory sample shall be prepared. The laboratory samples shall each be analysed in duplicate, and the duplicates designated x 111and x 112for sample A 1 , x 121and x 122for sample A 2 , and x 21and x 22for sample B. The six determinations shall be run in random order, by the same analyst on the same day using the same analytical equipment. NOTE By using method 2, the estimated precisions of primary sampling, sample processing and analysis can be obtained separately. However, the estimated values will be less precise than those obtained using method 1. 5.2.3 Sample processing method 3 (see Figure 4) From each of the two interleaved samples A and B, one laboratory sample shall be prepared. The two laboratory samples A and B shall be analysed in duplicate, and the measurements obtained shall be designated x 11and x 12for sample A, and x 21and x 22for sample B. The four determinations shall be run in random order, by the same analyst on the same day using the same analytical equipment. NOTE By using method 3, only the estimated precision of analysis and the combined precision of primary sampling and sample processing are obtained. BS ISO 12744:20064 Figure 1 — Example of a plan for interleaved duplicate sampling BS ISO 12744:2006 5Figure 2 — Flowsheet for sample processing method 1 Figure 3 — Flowsheet for sample processing method 2 Figure 4 — Flowsheet for sample processing method 3 BS ISO 12744:20066 6 Evaluation of experimental data 6.1 General The method for evaluation of experimental data shall be as specified in 6.2, 6.3 or 6.4, depending on the method of sample processing selected. 6.2 Sample processing method 1 a) Calculate the mean and range for each pair of duplicates: 12 1 () 2 ij ij ij xxx =+ (1) 112 ij ij R xx =− (2) where i = 1 and 2, representing interleaved samples A and B respectively; j = 1 and 2, representing laboratory samples A 1and A 2or B 1and B 2 . b) Calculate the mean of the mean value and range for each pair of duplicates: 12 1 () 2 iii xxx =+ (3) 212 ii R xx =− (4) c) Calculate the mean and range for each pair of interleaved samples, A and B: 12 1 () 2 xxx =+ (5) 312 R xx =− (6) d) Calculate the grand mean and the means of ranges R 1 , R 2and R 3 : 1 xx k = ∑ (7) 1 1 1 4 R R k = ∑(8) 2 2 1 2 R R k = ∑(9) 3 3 1 R R k = ∑(10) where k is the number of lots. e) Calculate the variances s 1 2 , s 2 2and s 3 2from the means of ranges 1 R , 2 R and 3 : R 22 11 () 4 sR π = (11) BS ISO 12744:2006 7 22 22 () 4 sR π = (12) 22 33 () 4 sR π = (13) where π/4 is a statistical factor relating range to variance for a pair of measurements. f) Conduct F-tests on the variances s 1 2 , s 2 2and s 3 2to determine whether their differences are statistically significant using the following procedure: 1) calculate the variance ratios s 2 2 /s 1 2and s 3 2 /s 2 2 ; 2) compare these ratios with the 95 % confidence F-ratios given in Table 1 for the number of degrees of freedom applicable to each variance estimate; 3) if the calculated variance ratio exceeds the F-ratio, partition the two variances into variance components, as their difference is statistically significant. If the calculated variance ratio does not exceed the F-ratio, the variances s 2 2and/or s 3 2cannot be meaningfully partitioned into variance components, and more data need to be collected. g) Assuming that the F-tests conducted in f) indicate that the differences between the variances s 1 2 , s 2 2and s 3 2are significant, calculate the estimated values of the variance of analysis (s A 2 ), sample processing (s P 2 ) and primary sampling (s S 2 1 ) as follows: 22 1 A s s = (14) 222 P21 1 2 s ss =− (15) 1 222 S32 1 2 s ss =− (16) h) Calculate the total variance of primary sampling, sample processing and analysis (s T 2 ) as follows: 1 2222 TSPA s sss =++ (17) i) Calculate the estimated values of the total standard deviation (s T ) and the standard deviations of p