ISO 12744:2006

INTERNATIONAL ISO
STANDARD 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



Reference number
ISO 12744:2006(E)
©
ISO 2006

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ISO 12744:2006(E)
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ISO 12744:2006(E)
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

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ISO 12744:2006(E)
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.

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INTERNATIONAL STANDARD ISO 12744:2006(E)

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.
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ISO 12744:2006(E)
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 Absolute 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
1
R Absolute difference between means for divided interleaved samples A and A , and B and B
2 1 2 1 2
R Mean absolute difference between means for divided interleaved samples A and A , and B and B , for k
2
1 2 1 2
lots
R Absolute 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
3
s Estimated value of standard deviation, σ
2
s Estimated variance from R
1
1
2
s Estimated variance from R
2 2
2
s Estimated variance from R
3
3
s Estimated standard deviation of analysis
A
s Estimated standard deviation of sample processing
P
s Estimated standard deviation of primary sampling
S
1
s Estimated standard deviation of primary sampling and sample processing
SP
s Estimated total standard deviation of primary sampling, sample processing and analysis
T
x First duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample A or B
i1
x Second duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample A or B
i2
x First duplicate result for interleaved sample, where i = 1 and 2 and indicates interleaved sample A or B, and
ij1
j = 1 or 2 and indicates laboratory samples A or A , and B or B
1 2 1 2
x Second duplicate result for sample, where i = 1 and 2 and indicates interleaved sample A or B, and j = 1 or 2
ij2
and indicates laboratory samples A or A , and B or B
1 2 1 2
x 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
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ISO 12744:2006(E)
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 , A ,
1 2
and B , B . These laboratory samples shall each be analysed in duplicate, and the duplicates designated x
1 2 111
and x for sample A , x and x for sample A , x and x for sample B , and x and x for sample
112 1 121 122 2 211 212 1 221 222
B . The eight determinations shall be run in random order, by the same analyst on the same day using the
2
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 and A . From sample B, only one laboratory
1 2
sample shall be prepared. The laboratory samples shall each be analysed in duplicate, and the duplicates
designated x and x for sample A , x and x for sample A , and x and x for sample B. The six
111 112 1 121 122 2 21 22
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 and x for sample A, and x and x for sample B. The four determinations shall be run in
11 12 21 22
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.

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ISO 12744:2006(E)

Figure 1 — Example of a plan for interleaved duplicate sampling
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ISO 12744:2006(E)

Figure 2 — Flowsheet for sample processing method 1

Figure 3 — Flowsheet for sample processing method 2

Figure 4 — Flowsheet for sample processing method 3
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ISO 12744:2006(E)
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:
1
xx=+()x (1)
ij ij12ij
2
R=−xx (2)
11ij ij2
where
i = 1 and 2, representing interleaved samples A and B respectively;
j = 1 and 2, representing laboratory samples A and A or B and B .
1 2 1 2
b) Calculate the mean of the mean value and range for each pair of duplicates:
1
xx=+()x (3)
ii12i
2
R=−xx (4)
21ii2
c) Calculate the mean and range for each pair of interleaved samples, A and B:
1
xx=+()x (5)
12
2
R=−xx (6)
31 2
d) Calculate the grand mean and the means of ranges R , R and R :
1 2 3
1
xx= (7)
∑
k
1
R = R (8)
1 1
∑
4k
1
R = R (9)
2 2
∑
2k
1
R = R (10)
3 3
∑
k
where k is the number of lots.
2 2 2
e) Calculate the variances s , s and s from the means of ranges R , R and R :
1 2 3
1 2 3
π
22
sR= () (11)
11
4
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ISO 12744:2006(E)
π
22
sR= () (12)
22
4
π
22
sR= () (13)
33
4
where π/4 is a statistical factor
...