ISO 17318:2015

Fertilizers and soil conditioners — Determination of arsenic, cadmium, chromium, lead and mercury contents

ISO 17318:2015 specifies the test methods for determination of metals soluble in nitric acid: arsenic, cadmium, chromium, lead, and mercury contents in fertilizers. ISO 17318:2015 is applicable to the analysis of arsenic, cadmium, chromium, lead, and mercury contents in fertilizers. Special attention should be given when analysing some micro-nutrients fertilizers.

Matières fertilisantes — Détermination de l'arsenic, du cadmium, du plomb, du chrome et du mercure dans les engrais

General Information

• Status: Published
• Publication Date: 02-Jun-2015
• ICS: 65.080 - Fertilizers
• Technical Committee: ISO/TC 134 - Fertilizers, soil conditioners and beneficial substances
• Drafting Committee: ISO/TC 134 - Fertilizers, soil conditioners and beneficial substances
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 06-Sep-2020

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17318
First edition
2015-06-01
Fertilizers and soil conditioners —
Determination of arsenic, cadmium,
chromium, lead and mercury contents
Matières fertilisantes — Détermination de l’arsenic, du cadmium, du
plomb, du chrome et du mercure dans les engrais
Reference number
ISO 17318:2015(E)
©
ISO 2015

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ISO 17318:2015(E)

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ISO 17318:2015(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 1
5 Apparatus and materials. 2
6 Procedure. 2
6.1 Sample preparation . 2
6.2 Preparation of the test solution . 2
6.3 Preparation of the blank test solution . 2
6.4 Preparation of the working standard solution . 2
6.5 Determination of arsenic, cadmium, chromium, lead and mercury contents by
inductively coupled plasma .
optical emission spectroscopy (ICP-OES) . 3
6.6 Calculation and expression of the results . 4
7 Precision . 4
7.1 Ring test . 4
7.2 Repeatability . 4
7.3 Reproducibility . 4
8 Test report . 4
Annex A (informative) Interlaboratory testing . 6
Bibliography .30
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ISO 17318:2015(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the 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 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. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list 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 meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 134, Fertilizers and soil conditioners.
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INTERNATIONAL STANDARD ISO 17318:2015(E)
Fertilizers and soil conditioners — Determination of
arsenic, cadmium, chromium, lead and mercury contents
1 Scope
This International Standard specifies the test methods for determination of metals soluble in nitric acid:
arsenic, cadmium, chromium, lead, and mercury contents in fertilizers.
This International Standard is applicable to the analysis of arsenic, cadmium, chromium, lead, and
mercury contents in fertilizers. Special attention should be given when analysing some micro-nutrients
fertilizers.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specification and test methods
3 Principle
Arsenic, cadmium, chromium, lead, and mercury in the test portion are extracted by means of nitric
acid digestion in a microwave digestion system. The digested solution will be measured by inductively
coupled plasma – optical emission spectroscopy (ICP-OES). Indium will be used as internal standard
substance when chromium or lead is determined.
NOTE An internal standard is recommended for metals to correct for solution matrix differences between
the calibration standards and the fertilizer digests, any other internal standard materials with equal effect could
be utilized, provided none of these are contained in the fertilizer samples.
4 Reagents
WARNING — Nitric acid is corrosive and oxidizer. The related operations shall be performed
in fume hood. This standard does not point out all possible safety problems, and the user shall
bear the responsibility to take proper safety and health measures, and ensure the operations
compliant with the conditions stipulated by the related laws and regulations of the state.
Use only reagents of recognized analytical grade, and water conforming to grade 3 of ISO 3696:1987.
4.1 Nitric acid, d = 1,40 g/ml, recommend to use trace element grade nitric acid.
4.2 Nitric acid solution, add 1 volume of nitric acid to 9 volume of water.
4.3 Standard stock solution of arsenic, cadmium, chromium, lead, mercury, 1 000 mg/l certificated
substance.
4.4 Indium standard stock solution, 1 000 mg/l.
Weigh In(NO ) × H O [containing 0,262 0 g In(NO ) ] to a 100 ml beaker, dissolved by nitric acid solution
3 3 2 3 3
(4.2), then transfer to a 100 ml volumetric flask, fill to the mark with nitric acid solution (4.2), and mix.
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ISO 17318:2015(E)

4.5 Indium standard solution, 5 mg/l.
Dilute 1 000 mg/l Indium standard stock solution with nitric acid solution (4.2) to 5 mg/l.
4.6 High-purity argon, content ≥ 99,999 %.
5 Apparatus and materials
Ordinary laboratory apparatus and the following:
5.1 Microwave digestion system.
5.2 Inductively coupled plasma — optical emission spectroscopy (ICP-OES), with a mixing device
to add an internal standard.
5.3 Sieve, with the aperture size of 0,50 mm.
6 Procedure
6.1 Sample preparation
Take a representative fertilizer subsample of 100 g. Grind it until it passes through a sieve of aperture
size 0,5 mm, mix thoroughly for reasons of homogeneity, place in a clean, and dry bottle with lid.
6.2 Preparation of the test solution
The replicate experiments shall be done for the determination.
Weigh 1 g sample (accurate to 0,1 mg, for fertilizer containing liming material or organic matrixes,
reduce the weight properly) and transfer into a digestion vessel, keep the sample from adhering to sides
of vessel. Place the digestion vessel into a fume hood, and add 10 ml of nitric acid (4.1). Predigest at room
temperature until vigorous foaming subsides. Then seal the vessel and put into the microwave digestion
system.
The ramped temperature program should be set under the instruction of the instrument manual.
Ramping temperature from ambient to 160 °C slowly in 10 min, and then hold at 160 °C for another
10 min. Cool vessels to room temperature, vent, and transfer digests to a 100 ml volumetric flask, fill
to the mark with water, and mix. Then the solution should be filtered through a dry, folded filter paper.
Discard the first few millilitres portions of filter solution.
6.3 Preparation of the blank test solution
The experiment steps are the same as the preparation of the test solution, with the exception of adding
the sample.
6.4 Preparation of the working standard solution
Pipet appropriate amount of element standard stock solution (4.3), dilute with nitric acid solution (4.2)
into volumetric flasks according to Table 1, prepare blended multi-element standard solution series.
Table 1 — Typical concentrations of blended multi-element standard solutions (mg/l)
Element As Cd Cr Pb Hg
standard
No. 0 0 0 0 0 0
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ISO 17318:2015(E)

Table 1 (continued)
Element As Cd Cr Pb Hg
standard
No. 1 0,02 0,02 0,02 0,02 0,02
No. 2 0,1 0,1 0,1 0,1 0,1
No. 3 0,5 0,5 0,5 0,5 0,5
No. 4 2,0 2,0 2,0 2,0 2,0
No. 5 5,0 5,0 5,0 5,0 5,0
NOTE Useful concentrations for standardization can be quite different for different instrument types.
6.5 Determination of arsenic, cadmium, chromium, lead and mercury contents by
inductively coupled plasma–optical emission spectroscopy (ICP-OES)
Before the determination, refer to the instrument operation manual. Select the best operation conditions
in accordance with the elements properties. The recommended operating conditions of ICP are listed in
Table 2. Other conditions which can achieve the same results can also be used.
Table 2 — Recommended operating conditions of ICP
Wavelength As 189,042 nm, Cd 228,802 nm, Pb 220,353 nm, Cr 283,563 nm, Hg
184,950 nm, In 230,606 nm.
Maximum integration time Low wavelength scale: 10 s, High wavelength scale: 10 s
Flush velocity of 50 r/min
sample pump
Analysis velocity of sample pump 50 r/min
Sample pump stable time 5 s
Light source Radiofrequency, power of 1 150 W
Flow rate of auxiliary gas 0,5 l/min
Flow rate of gas within the nebu- 0,5 l/min
lizer
NOTE Special attention should be given on the wavelength resolution of ICP instrument, the use of a second
or third wavelength for confirmation purposes may be recommended, if appropriate.
Determine the working standard solutions (6.4), the blank test solution (6.3), and the test solutions
(6.2) in order. When the concentration of Cr or Pb are determined, use the 5mg/l indium standard
solution (4.5) as the internal standard substance, mix the internal standard substance solution and test
solution (1:5 V/V) by a mixing device. If the concentration of the element in the test solution exceeds
the concentration range of the standard curve, dilute the test solution to a certain ratio with nitric acid
solution (4.2) for re-determination.
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ISO 17318:2015(E)

6.6 Calculation and expression of the results
The determination results of elements (mg/kg) are calculated as follows:
cc− ××100 D
()
0
X = (1)
m
where
C is the concentration in mg/l, of the determined element in the test solution;
c is the concentration in mg/l, of the determined element in the blank test solution;
0
100 is the total volume in ml, of the test solution;
D is the dilution ratio of the test solution when required, otherwise D is removed or assigned
a value of 1;
m is the mass in g, of the test portion.
The determination result is the arithmetic average of the parallel determination results.
7 Precision
7.1 Ring test
Details of Ring test on the precision of the method are summarized in Annex A.
7.2 Repeatability
Element As Cd Cr Pb Hg
Repeatability limit,
0,621 0,586 2 0,755 2 0,849 9 0,582 4
0,227x 0,173x 0,145x 0,100x 0,252x
r, mg/kg
7.3 Reproducibility
Element As Cd Cr Pb Hg
Reproducibility
0,809 1,116 7 0,521 9 0,643 2 0,771 5
0,316x 0,048x 1,017x 0,499x 0,374x
limit, R, mg/kg
8 Test report
The test report shall contain at least the following information:
a) all information necessary for the complete identification of the sample;
b) test method used with reference to this International Standard (i.e. ISO 17318);
c) test results obtained;
d) date of sampling and sampling procedure (if known);
e) date when the analysis was finished;
f) whether the requirement of the repeatability limit has been fulfilled.
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ISO 17318:2015(E)

All operating details not specified in this standard, or regarded as optional, together with details of any
incidents occurred when performing the method, which might have influenced the test results.
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ISO 17318:2015(E)

Annex A
(informative)

Interlaboratory testing
A.1 Overview
The International Laboratories Ring Tests of this International Standard have been accomplished
from Sep. 2012 to Dec. 2012. There are 14 laboratories participating in the two parallel tests on each
four samples. This international ring test was conducted by Shanghai Research Institute of Chemical
Industry, P. R. China, the statistician analysis and final report was prepared by Shanghai Research
Institute of Chemical Industry, P. R. China.
The following are the14 laboratories participating in the two parallel tests on each four samples.
— Shanghai Research Institute of Chemical Industry, Testing Center, China
— CF Industries Laboratory, USA
— Jiangsu Province Products Quality Supervising and Testing Institute, China
— Hunan Province Products Quality Supervising and Testing Institute, China
— Shandong Province Products Quality Supervising and Testing Institute, China
— Guizhou Province Products Quality Supervising and Testing Institute, China
— Guizhou Kailin Quality Testing Center, China
— Guangxi Zhuang Autonomous Region Products Quality Supervising and Testing Institute, China
— Heilongjiang Province Products Quality Supervising and Testing Institute, China
— Xingjiang Uygur Autonomous Region Products Quality Supervising and Testing Institute, China
— Yunnan Province Chemical Products Quality Supervising and Testing Center, China
— Shanghai Entry-Exit Inspection and Quarantine Bureau, China
— Yunnan Province Products Quality Supervising and Testing Institute, China
— Shenyang Fertilizer Quality Supervising and Testing Center, Ministry of Agriculture, China
NOTE The above sequence has nothing to do with the order of the tests in the laboratory.
The test method described in this International Standard was adopted here for determination of arsenic,
cadmium, lead, chromium, and mercury contents in the fertilizer samples.
Four different kinds of fertilizer samples were used during the ring test, and constitute a gratitude of
mean levels of 4. There are sample A-NPK compound fertilizer, sample B-NPK complex fertilizer, sample
C-diammonium phosphate, and sample D-organic fertilizer. The arsenic, cadmium, lead, chromium and
mercury contents in all of the 4 fertilizer samples lie in 8 mg/kg to 120 mg/kg.
The precision of the test results is evaluated based on ISO 5725-2:1994.
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ISO 17318:2015(E)

A.2 Statistical analysis of the test results of arsenic contents
A.2.1 Original test results
There are 11 laboratories has participated in the determination of arsenic contents in fertilizers. The
test results were listed in Table A.1, with the unit of mg/kg.
Table A.1 — Original test results of the determination of arsenic contents
Level j
Laboratory i
A B C D
1 75,03 75,91 94,39 96,57 12,61 16,14 60,11 59,50
2 74,56 71,86 94,85 94,27 14,37 13,61 55,27 54,27
3 76,13 79,51 103,05 101,87 15,45 15,21 60,00 60,24
4 80,10 76,92 99,79 99,49 14,50 14,62 57,20 57,48
5 76,56 76,68 100,03 99,31 16,82 16,11 62,91 61,86
6 76,37 74,85 99,41 97,61 13,97 14,39 56,91 57,35
7 69,87 71,89 89,27 93,08 14,57 14,98 53,63 50,82
8 66,87 69,84 94,61 92,47 13,43 14,34 51,94 51,88
9 76,14 76,28 100,90 100,02 14,98 15,82 57,26 58,08
10 74,99 74,94 99,03 98,03 14,01 14,65 57,85 56,51
11 80,37 80,14 105,22 107,16 16,04 16,59 59,42 61,85
A.2.2 Cell means
The cell means of the determination of arsenic contents were listed in Table A.2, with the unit of mg/kg.
Table A.2 — Cell means of the determination of arsenic contents
Level j
Laboratory i
A B C D
1 75,470 95,480 14,375 59,805
2 73,210 94,560 13,990 54,770
3 77,820 102,460 15,330 60,120
4 78,510 99,640 14,560 57,340
5 76,620 99,670 16,465 62,385
6 75,610 98,510 14,180 57,130
7 70,880 91,175 14,775 52,225
8 68,355 93,540 13,885 51,910
9 76,210 100,460 15,400 57,670
10 74,965 98,530 14,330 57,180
11 80,255 106,190 16,315 60,635
A.2.3 Cell absolute differences
The cell absolute differences of the determination of arsenic contents were listed in Table A.3, with the
unit of mg/kg.
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s
h
ISO 17318:2015(E)

Table A.3 — Cell absolute differences of the determination of arsenic contents
Level j
Laboratory i
A A A A
1 0,88 2,18 3,53 0,61
2 2,70 0,58 0,76 1,00
3 3,38 1,18 0,24 0,24
4 3,18 0,30 0,12 0,28
5 0,12 0,72 0,71 1,05
6 1,52 1,80 0,42 0,44
7 2,02 3,81 0,41 2,81
8 2,97 2,14 0,91 0,06
9 0,14 0,88 0,84 0,82
10 0,05 1,00 0,64 1,34
11 0,23 1,94 0,55 2,43
A.2.4 Scrutiny of results for consistency and outliers
Graphical consistency technique by Mandel’s h and k statistics:
Calculate the between-laboratory consistency statistic h, as well as the within-laboratory consistency
statistic k, for each level of each laboratory. Plot the h and k values for each cell in order of laboratory
respectively, to get the Mandel’s h and k graphs.
,
,
,
,
,
i
Figure 1 — Mandel’s between-laboratory consistency statistic, h, grouped by laboratories
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s k
ISO 17318:2015(E)

,
,
,
,
i
Figure 2 — Mandel’s within-laboratory consistency statistic, k, grouped by laboratories
Horizontal dotted lines in figures above represent 1 % and 5 % critical values of Mandel’s h and k
statistics, respectively.
The h graph has shown that laboratory 8 had a straggler on level A, and laboratory 11 had a straggler on
level B, while no outlier has been founded herein.
The k graph has exhibited rather large variability between replicate test results for laboratory 7 on
levels B and D, as well as laboratory 1 on level C.
Cochran’s test
Application of Cochran’s test led to the values of the test statistic C given in Table A.4.
Table A.4 — Values of Cochran test statistic, C
Level j A B C D Type of test
Cochran’s test
C 0,254 0,415 0,769 0,414
statistics
Stragglers
Cochran’s
(P = 11) 0,570 0,570 0,570 0,570
critical
Outliers
values
(P = 11) 0,684 0,684 0,684 0,684
If the test statistic is greater than its 5 % critical value and less than or equal to its 1 % critical value, the
item tested is regarded as a straggler;
If the test statistic is greater than its 1 % critical value, the item tested is regarded as an outlier.
Cochran’s test here shown that the test statistic reached 0,769, calculated by the cell absolute difference
(3,53) from laboratory 1 on level C.
The Cochran’s critical value at the 1 % significance level was 0,684, therefore the test results from
laboratory 1 on level C is a outlier, which should be discarded here.
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ISO 17318:2015(E)

Cochran’s test was repeated on the remaining tests values from the 10 laboratories on level C, the
test statistic obtained this time was 0,221, which is less than the Cochran’s critical value at the 5 %
significance level (0,602, P = 10). So we have confirmed that no straggler exist this time (and of course
no outlier, either).
Grubbs’ test
Application of Grubbs’ test to cell means led to the values of the test statistic G shown in Table A.5.
Table A.5 — Application of Grubbs’ test to cell means
Level j;P Single low Single high Double low Double high Type of test
A;11 2,027 1,465 0,301 5 0,629 9
B;11 1,641 1,866 0,529 2 0,461 8
Grubbs’ test sta-
tistics
C;10 1,121 1,666 1,966 5 0,301 1
D;11 1,630 1,492 0,386 7 0,615 7
Stragglers
P = 10 2,290 2,290 0,186 4 0,186 4
Grubbs’
P = 11 2,355 2,355 0,221 3 0,221 3
critical
Outliers
values
P = 10 2,482 2,482 0,115 0 0,115 0
P = 11 2,564 2,564 0,144 8 0,144 8
For the Grubbs’ test for one outlying observation, outliers and stragglers give rise to values which are
larger than its 1 % and 5 % critical values respectively.
For the Grubbs’ test for two outlying observation, outliers and stragglers give rise to values which are
smaller than its 1 % and 5 % critical values respectively.
Application of Grubbs’ test to our cell means here confirms no stragglers (and of course no outlier, either).
A.2.5 Calculation of the general mean and standard deviations
Calculation of the general mean, s , s of arsenic contents in each sample has led to Table A.6, with the
r R
unit of mg/kg.
Table A.6 — Calculation results of the general mean, s , s of arsenic contents
r R
Sample/Level C D A B
Number of Labora-
tories 11 11 11 11
Outliers 1 0 0 0
General mean, x 14,92 57,38 75,26 98,20
Repeatability stand-
ard deviation, s 0,433 0,931 1,429 1,261
r
Reproducibility
standard deviation,
s 0,975 3,419 3,554 4,373
R
A.2.6 Dependence of precision on general mean, x
From Table A.6 it seems clear that the standard deviations tend to increase with higher values of x, so it
is likely that it might be permissible to establish some form of functional relationship.
The actual fitting calculation has shown well linear correlation between log , log with log , respectively,
sr SR x
the formulae were shown as follows:
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2
   log = 0,621 log − 1,090 7   R = 0,941
sr x
2
   log = 0,809 log − 0,947     R = 0,982 8
SR x
A.2.7 Final Values of precision
The precision of the as-contents measurement method should be quoted as follows:
0,621
— repeatability standard deviation: s = 0,081 2x
r
0,809
— reproducibility standard deviation: s = 0,113x
R
The conclusion above were determined from a uniform-level experiment involving 11 laboratories, in
which one test value from a laboratory on level C has been discarded as an outlier.
(Based on the formulae above, for fertilizer sample with As content at 20 mg/kg, the repeatability standard
deviation should be 0,522 mg/kg, the reproducibility standard deviation should be 1,275 mg/kg; the
repeatability limit should be 1,46 mg/kg, the reproducibility limit should be 3,57 mg/kg)
A.3 Statistical analysis of the test results of cadmium contents
A.3.1 Original test results
There are 14 laboratories has participated in the determination of cadmium contents in fertilizers. The
test results were listed in Table A.7, with the unit of mg/kg.
Table A.7 — Original test results of the determination of cadmium contents
Level j
Laboratory i
A B C D
1 49,83 50,77 86,36 88,12 19,70 19,87 69,09 67,71
2 48,48 50,78 92,47 94,71 18,86 20,02 69,55 72,06
3 47,41 47,36 90,51 91,04 19,15 19,05 71,28 71,45
4 47,53 49,40 92,78 92,53 19,69 19,77 72,44 72,77
5 46,35 46,22 88,70 88,99 18,63 18,94 70,30 70,51
6 49,78 49,38 94,13 94,08 19,11 19,05 71,36 70,73
7 48,91 47,83 90,83 91,49 19,14 18,40 69,69 70,01
8 51,13 50,95 97,52 97,85 19,33 19,23 74,61 72,21
9 47,42 47,19 90,84 92,05 18,88 18,97 68,34 67,80
10 49,16 49,24 95,02 95,12 19,98 19,16 72,11 72,10
11 48,68 48,83 93,56 93,51 18,93 18,95 71,94 71,77
12 48,43 48,22 91,44 90,79 18,87 19,16 70,93 69,54
13 49,16 48,90 94,69 95,76 20,14 20,26 70,61 73,44
14 48,97 48,30 96,06 97,31 19,07 18,66 68,82 68,89
A.3.2 Cell means
The cell means of the determination of cadmium contents were listed in Table A.8, with the unit of
mg/kg.
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Table A.8 — Cell means of the determination of cadmium contents
Level j
Laboratory i
A B C D
1 50,300 87,240 19,785 68,400
2 49,630 93,590 19,440 70,805
3 47,385 90,775 19,100 71,365
4 48,465 92,655 19,730 72,605
5 46,285 88,845 18,785 70,405
6 49,580 94,105 19,080 71,045
7 48,370 91,160 18,770 69,850
8 51,040 97,685 19,280 73,410
9 47,305 91,445 18,925 68,070
10 49,200 95,070 19,570 72,105
11 48,755 93,535 18,940 71,855
12 48,325 91,115 19,015 70,235
13 49,030 95,225 20,200 72,025
14 48,635 96,685 18,865 68,855
A.3.3 Cell absolute differences
The cell absolute differences of the determination of cadmium contents were listed in Table A.9, with the
unit of mg/kg.
Table A.9 — Cell absolute differences of the determination of cadmium contents
Level j
Laboratory i
A B C D
1 0,94 1,76 0,17 1,38
2 2,30 2,24 1,16 2,51
3 0,05 0,53 0,10 0,17
4 1,87 0,25 0,08 0,33
5 0,13 0,29 0,31 0,21
6 0,40 0,05 0,06 0,63
7 1,08 0,66 0,74 0,32
8 0,18 0,33 0,10 2,40
9 0,23 1,21 0,09 0,54
10 0,08 0,10 0,82 0,01
11 0,15 0,05 0,02 0,17
12 0,21 0,65 0,29 1,39
13 0,26 1,07 0,12 2,83
14 0,67 1,25 0,41 0,07
A.3.4 Scrutiny of results for consistency and outliers
Graphical consistency technique by Mandel’s h and k statistics:
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s h
s k
ISO 17318:2015(E)

Calculate the between-laboratory consistency statistic h, as well as the within-laboratory consistency
statistic k, for each level of each laboratory. Plot the h and k values for each cell in order of laboratory
respectively, to get the Mandel’s h and k graphs.
,
,
,
,
,
,
i
Figure 3 — Mandel’s between-laboratory consistency statistic, h, grouped by laboratories
,
,
,
i
Figure 4 — Mandel’s within-laboratory consistency statistic, k, grouped by laboratories
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ISO 17318:2015(E)

Horizontal dotted lines in figures above represent
...