SIST-TS CEN/TS 16490:2013
(Main)Fertilizers - Comparison of the CEN/TC 260/WG 7 ring test results with tolerances given in the Regulation (EC) Nr 2003/2003 Annex II and conclusions
Fertilizers - Comparison of the CEN/TC 260/WG 7 ring test results with tolerances given in the Regulation (EC) Nr 2003/2003 Annex II and conclusions
In Regulation (EC) No. 2003/2003 [2] tolerance limits are mentioned for nutrient contents in mineral fertilizers (Annex II of Regulation (EC) No. 2003/2003) as well as prescribed methods for control purposes (Annex IV of Regulation (EC) No. 2003/2003). Prior to the work done by CEN/TC 260 following Mandate M/335, no statistical data were available for the official analytical methods to be applied. Due to the standardization work done for this mandate, statistical data have been generated as ring testing was a major topic in this mandate. This Technical Specification describes to what extent the presently applied tolerances are in line with the obtained precision data from the analytical methods studied. The purpose of this document is to give feedback on the applied tolerances within Regulation (EC) No. 2003/2003 based on the method evaluation done as an outcome of the work executed by CEN/TC 260/WG 7 according to Mandate M/335. This evaluation of the tolerances was part of Mandate M/418.
Düngemittel - Vergleich der Ringversuchsergebnisse der CEN/TC 260/WG 7 mit den in der Verordnung (EG) Nr. 2003/2003 Anhang II angegebenen Toleranzen und Schlussfolgerungen
In der Verordnung (EG) Nr. 2003/2003 [2] sind sowohl Toleranzgrenzen für Nährstoffgehalte in mineralischen Düngemitteln (Verordnung (EG) Nr. 2003/2003, Anhang II) als auch vorgeschriebene Verfahren für Kontroll-zwecke (Verordnung (EG) Nr. 2003/2003, Anhang IV) angegeben.
Bevor CEN/TC 260, dem Mandat M/335 folgend, mit der Arbeit begann, waren keine statistischen Daten für die anzuwendenden offiziellen Analysenverfahren verfügbar. Im Ergebnis der im Rahmen dieses Mandats durchgeführten Normungsarbeit wurden die entsprechenden statistischen Daten ermittelt. Ringversuche waren die wesentliche Aufgabenstellung innerhalb dieses Mandats.
Diese Technische Spezifikation beschreibt, inwieweit sich die derzeit geltenden Toleranzen in Übereinstimmung mit den aus den untersuchten Analysenverfahren erhaltenen Präzisionsdaten befinden.
Der Zweck dieses Dokumentes ist, auf der Grundlage der Verfahrensbewertung, die das Ergebnis der vom CEN/TC 260/WG 7 nach dem Mandat M/335 durchgeführten Arbeit darstellt, ein Feedback über die innerhalb der Verordnung (EG) Nr. 2003/2003 geltenden Toleranzen zu geben. Diese Bewertung der Toleranzen war Teil des Mandats M/418.
Engrais - Comparaison des résultats des essais interlaboratoires menés par le CEN/TC 260/WG 7 avec les tolérances données dans le règlement (CE) n°2003/2003 Annexe II et conclusions
Le Règlement (CE) n° 2003/2003 [2] fixe des limites de tolérance de la teneur en éléments fertilisants des engrais minéraux (Annexe II du Règlement (CE) n° 2003/2003) et spécifie des méthodes pour le contrôle (Annexe IV du Règlement (CE) n° 2003/2003).
Préalablement au travail effectué par le CEN/TC 260 à la suite du mandat M/335, aucune donnée statistique relative aux méthodes d'analyse officielles à appliquer n'était disponible. En raison du travail de normalisation accompli dans le cadre de ce mandat, des données statistiques ont été générées puisque les essais interlaboratoires étaient l'un des principaux sujets du mandat.
La présente Spécification technique décrit la mesure dans laquelle les tolérances actuellement appliquées sont en accord avec les données de fidélité des méthodes d'analyse étudiées.
L'objectif du présent document est de fournir un retour d'informations sur les tolérances appliquées dans le cadre du Règlement (EC) n° 2003/2003 à partir d'une évaluation des méthodes qui résulte du travail accompli par CEN/TC 260/WG 7 conformément au mandat M/335. Cette évaluation des tolérances faisait partie du mandat M/418.
Gnojila - Primerjava rezultatov krožnih preskusov CEN/TC 260/WG 7 z dovoljenimi odstopanji, navedenimi v Uredbi (ES) št. 2003/2003 Priloga II in sklepi
V Uredbi (ES) št. 2003/2003 [2] so navedene meje dovoljenih odstopanj za vsebnost hranil v mineralnih gnojilih (Priloga II k Uredbi (ES) št. 2003/2003) ter predpisane metode za namene kontrole (Priloga IV k Uredbi (ES) št. 2003/2003). Pred delom, ki ga je opravil odbor CEN/TC 260 v mandatu M/335, statistični podatki za uradne preskusne metode, ki jih je treba uporabiti, niso bili na voljo. Zaradi priprave standardov v tem mandatu so bili zbrani statistični podatki, saj so bili krožni preskusi pomembna tema v tem mandatu. Ta tehnična specifikacija opisuje, do kakšne mere so dovoljena odstopanja, ki se trenutno uporabljajo, v skladu z dobljenimi podatki o natančnosti iz preučevanih preskusnih metod. Namen tega dokumenta je podati povratne informacije v zvezi z uporabljenimi dovoljenimi odstopanji v okviru Uredbe (ES) št. 2003/2003 na podlagi ocene metode, ki se je izvedla kot posledica dela, ki ga je izvedel odbor CEN/TC 260/WG 7 v skladu z mandatom M/335. Ta ocena dovoljenih odstopanj je bila del mandata M/418.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TS CEN/TS 16490:2013
01-maj-2013
Gnojila - Primerjava rezultatov krožnih preskusov CEN/TC 260/WG 7 z dovoljenimi
odstopanji, navedenimi v Uredbi (ES) št. 2003/2003 Priloga II in sklepi
Fertilizers - Comparison of the CEN/TC 260/WG 7 ring test results with tolerances given
in the Regulation (EC) Nr 2003/2003 Annex II and conclusions
Düngemittel - Vergleich der Ringversuchsergebnisse der CEN/TC 260/WG 7 mit den in
der Verordnung (EG) Nr. 2003/2003 Anhang II angegebenen Toleranzen und
Schlussfolgerungen
Engrais - Comparaison des résultats des essais interlaboratoires menés par le CEN/TC
260/WG 7 avec les tolérances données dans le règlement (CE) n°2003/2003 Annexe II
et conclusions
Ta slovenski standard je istoveten z: CEN/TS 16490:2013
ICS:
65.080 Gnojila Fertilizers
SIST-TS CEN/TS 16490:2013 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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TECHNICAL SPECIFICATION
CEN/TS 16490
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
April 2013
ICS 65.080
English Version
Fertilizers - Comparison of the CEN/TC 260/WG 7 ring test
results with tolerances given in the Regulation (EC) Nr
2003/2003 Annex II and conclusions
Engrais - Comparaison des résultats des essais Düngemittel - Vergleich der Ringversuchsergebnisse der
interlaboratoires menés par le CEN/TC 260/WG 7 avec les CEN/TC 260/WG 7 mit den in der Verordnung (EG) Nr.
tolérances données dans le règlement (CE) n°2003/2003 2003/2003 Anhang II angegebenen Toleranzen und
Annexe II et conclusions Schlussfolgerungen
This Technical Specification (CEN/TS) was approved by CEN on 12 February 2013 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 16490:2013: E
worldwide for CEN national Members.
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Contents Page
Foreword .3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions .5
4 Statistical method validation .6
4.1 General .6
4.2 Approach taken by CEN/TC 260/WG 7 .6
4.3 Statistical data: results versus tolerances .6
4.4 Refined statistical analysis .7
4.5 Field data .7
5 Conclusions .8
Annex A (informative) Statistical data of the inter-laboratory tests and findings . 10
A.1 General . 10
A.2 Nitrogen . 10
A.3 Phosphate . 13
A.4 Potassium . 15
A.5 Sulfur . 15
A.6 Chloride . 18
A.7 Secondary nutrients . 18
Annex B (informative) Refined statistical evaluation . 26
B.1 General . 26
B.2 Meaning of symbols . 26
B.3 Tolerances for SO . 27
3
B.4 Tolerances for CaO, MgO. Na O and Cl . 28
2
B.5 Refinement of results . 32
B.6 Comments . 32
Bibliography . 33
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Foreword
This document (CEN/TS 16490:2013) has been prepared by Technical Committee CEN/TC 260 “Fertilizers
and liming materials”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Croatia, Cyprus,
Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,
Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
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Introduction
Following a request from the European Commission (Mandate M/418), an evaluation was done of the existing
tolerances as per Regulation (EC) No. 2003/2003. Input for this evaluation was derived from the precision
data obtained via the several ring tests that have been made according to Mandate M/335.
As to exclude eventual interference from effects due to inhomogeneity of physically blended grades, no blends
have been included in the ring tests; test samples have been limited and chosen as to be representing some
main product grades sold within the EU.
The statistical evaluation has been done in line with ISO 5725-2 and whenever deemed necessary for
appropriate evaluation and interpretation of the test results, some extra statistical evaluation was made on the
test data.
As to judge to what extent problems arise in case of enforcement controls, some field data have been
analysed as to verify to what extent actual conflicts exist in between test results from official controls and
applied tolerances.
The evaluation revealed no real need for adjustments to tolerances as they relate to analytical variability.
However, it should be emphasised that the tolerances given in Regulation 2003/2003 relate not only to
analytical variability but to the total variability including allowances for sampling error and product variability.
Finally if the European Commission sees the necessity of further method improvements, then one could
consider a project entitled to develop an alternative method. Only following a full evaluation including ring
testing, a final judgment can be made if the newly developed method could be a candidate for replacement of
the existing one(s) assuming better accuracy data.
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1 Scope
In Regulation (EC) No. 2003/2003 [2] tolerance limits are mentioned for nutrient contents in mineral fertilizers
(Annex II of Regulation (EC) No. 2003/2003) as well as prescribed methods for control purposes (Annex IV of
Regulation (EC) No. 2003/2003).
Prior to the work done by CEN/TC 260 following Mandate M/335, no statistical data were available for the
official analytical methods to be applied. Due to the standardization work done for this mandate, statistical
data have been generated as ring testing was a major topic in this mandate.
This Technical Specification describes to what extent the presently applied tolerances are in line with the
obtained precision data from the analytical methods studied.
The purpose of this document is to give feedback on the applied tolerances within Regulation (EC)
No. 2003/2003 based on the method evaluation done as an outcome of the work executed by
CEN/TC 260/WG 7 according to Mandate M/335. This evaluation of the tolerances was part of Mandate
M/418.
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 5725-1:1994, Accuracy (trueness and precision) of measurement methods and results — Part 1: General
principles and definitions
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
tolerance (T)
variation including manufacturing, raw materials, sampling and analytical methods
3.2
repeatability limit (r)
the value less than or equal to which the absolute difference between two test results obtained under
repeatability conditions may be expected to be with a probability of 95 %
[SOURCE: ISO 5725-1:1994]
Note 1 to entry: In other words, r is the minimum difference between two results in order to be statistically different,
under repeatability conditions, at a 95 % probability level.
3.3
reproducibility limit (R)
the value less than or equal to which the absolute difference between two test results obtained under
reproducibility conditions may be expected to be with a probability of 95 %
[SOURCE: ISO 5725-1:1994]
Note 1 to entry: In other words, R is the minimum difference between two results in order to be statistically different,
under reproducibility conditions, at a 95 % probability level.
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4 Statistical method validation
4.1 General
European laboratories were involved, including as well private, industry, official as commercial laboratories.
ISO 5725-2 was applied as standard for ring testing and statistical evaluation of its results.
In general, legislative tolerances are given to accommodate variability in raw materials, manufacturing,
sampling and analytical routines.
4.2 Approach taken by CEN/TC 260/WG 7
4.2.1 Product selection
The European market is characterised by a broad portfolio of different types of fertilizer grades, Hence there
was a need for selection of a limited number of products to be tested for the ring-test(s). Aim during the
selection process was to get fertilizer samples tested reflecting some main grades sold in the EEC.
4.2.2 Samples and their preparation
In order to be able to evaluate the precision data of the method as such, samples have been taken to the
utmost extent as a spot (not agglomerated) sample out of a bulk production. This was done on purpose as to
reduce the possible variation originating from raw materials, manufacturing and sampling procedure.
Furthermore, all samples have been ground before distribution to the participating labs. Only solid,
homogeneous samples and liquid samples have been used; no blends. The aim was to work with a limited
number of samples, representing the main fertilizer grades applied.
4.2.3 Laboratories involved
The participation of the laboratories was on a voluntary basis, enabling as well private and industry, official
and commercial laboratories to contribute. As far as the lab proficiency concerns, the ring test set-up did not
require a familiarisation step for each of the individual participating laboratories nor for the methods evaluated.
The chosen approach does not imply any assurance on the degree of experience and routine of the labs
involved with the method under investigation and reflects the day-to-day situation as is.
4.2.4 Data evaluation
As already stated, ISO 5725-2 has been applied as the standard for the statistical data evaluation. However,
for some methods a more in depth approach has been made, with the support of an expert statistician, due to
the fact that the reproducibility parameters seemed to be in conflict with the existing tolerances. Based on this
refined statistical analysis, it has been the intention to come up with adequate tolerances.
As stated in [1], R should be ≤ 0,7 T. In case this condition is not fulfilled, one should from a theoretical
perspective considering the following alternative options:
improve the method of analysis;
propose an alternative method with better performance;
increase the tolerances.
4.3 Statistical data: results versus tolerances
The ring test data and findings are given in the informative Annex A.
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4.4 Refined statistical analysis
Despite the method refinements to the determination of water soluble sulfur and water soluble calcium,
reproducibility figures could not be improved substantially. Therefore, a more in-depth statistical analysis has
been performed by an expert statistician. The main principles are described below; the detailed information
can be consulted in Annex B.
In a first step, after applying the classical criteria for removing outliers of a population of data (see
ISO 5725-2), it could be concluded that the reproducibility data were in conflict with the existing tolerances.
A substantial number of test results show high R values which implies that the methods only comply with
tolerance substantially higher than the existing ones. In order to improve these reproducibility data, data sets
outside the 99,9 % confidence interval (after removal of outliers according to Grubb’s and Cochran’s tests)
have been removed. The s calculated from the remaining data is used to find a more adequate tolerance
R
value and at the same time comply with the performance of the method.
The same exercise has been performed for the total sulfur content.
Further, the remaining data population has been crosschecked with the official tolerances. However, still
conflicts were observed.
In a final step, it has been attempted to derive, based on statistical principles, reasonable tolerances for the
concerned nutrients.
4.5 Field data
In order to cross-check the outcome of the statistical evaluation of official methods versus tolerances in place
and verify the necessity for eventual adjustment of the existing tolerance limits, a population of obtained
anonymised test results have been evaluated. The test results submitted were data derived from official
controls (enforcement) and covering data from nutrient analysis on various fertilizer types such as: calcium
ammonium nitrate (CAN), CAN+MgO and NPK. In total about 450 analyses were presented, covering analysis
of Nitrogen, Sulfur, Magnesium and Phosphorus.
Sampling as well as analyses has been conducted according to EC methods.
These data have only been used to check whether problems arise in case of enforcement controls or not. The
enforcement data have not been evaluated statistically on repeatability or reproducibility. Neither have they
been used to evaluate the precision or correctness of the data obtained with CEN methods.
Tables 1 to 3 summarise data for fertilizer types that were numerously represented.
Table 1 — Product type: CAN27
Component Declared value Number of analyses Deviation from declaration Out of tolerance
% %
N total 27 30 -0,4 to +0,6 No
N NH 13,5 30 -0,4 to +0,5 No
4
Table 2 — Product type: CAN27 + MgO
Component Declared value Number of Deviation from Out of tolerance
% analyses declaration
%
N total 27 20 -0,5 to +0,6 No
N NH 13,5 20 -0,6 to +0,5 No
4
MgO 4 20 -0,04 to +0,4 No
MgO (ws) 1 to 1,8 20 -0,96 to +1,0 Yes
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Table 3 — Product type: NPK containing sulfur
Component Declared value Number of Deviation from Out of tolerance
% analyses declaration
%
N total 15 to 16 12 -0,2 to +0,8 No
S 2 to 4 9 +0,3 to 2,31 No
S (ws) 1,6 to 3,2 10 -0,3 to +1,4 No
P O (citrate) 15 10 -1,3 to +0,7 No
2 5
As can be seen from Tables 1 to 3, about 30 samples of CAN have been analysed and no exceeding of the
tolerances was detected for the nitrogen content.
For the 20 samples of CAN + MgO that have been analysed no exceeding of tolerances for nitrogen and
magnesium was found, except for MgO water soluble where a few deviations were identified.
About 15 samples of S containing NPK showed no exceeding of tolerances, neither for nitrogen, sulfur or
phosphorus.
Based on these data, one can conclude that there is no urgent need for adjustments to tolerances, however it
is obvious that deviation from declared values are larger for MgO and S compared to those for nitrogen.
5 Conclusions
In the frame of the mandate from the European Commission, and given the working conditions of WG 7, ring
tests have been performed using a limited number of samples, representing the main fertilizer grades on the
market. However, no physically blended grades have been used in the ring tests. Possible effects due to
inhomogeneity of physically blended grades are therefore not reflected in the statistical evaluation of the
various methods.
Based on evaluation of precision data there is in general no direct need for adaption of the existing tolerances
as they relate to analytical variability (see Introduction). However, some discrepancy between the tolerances
and the statistical data of the ring tests has been revealed. It concerns mainly the determination of calcium
and magnesium, in particular related to the water soluble part. To a lesser extent also the determination of
sulfur and more specifically the water soluble (ws) part, is concerned.
Therefore we do not recommend changing the applied tolerance limits from Regulation (EC) No 2003/2003 to
the methods that have been evaluated, with exception of the nutrients mentioned above. The evaluation of a
data set of enforcement controls seems to support this conclusion. However, since analytical variability is
shown to account for the entire tolerances in Regulation 2003/2003, consideration must be given to increasing
the individual tolerances to take account of sampling and product variability.
Regarding the method for determination of water soluble calcium, WG 7 has been exploring several
possibilities to improve the accuracy of this method. Nevertheless, no major progress has been achieved in
improving especially the reproducibility. Also a bench-mark with other legislative frames did not reveal better
and alternative methods, as the water soluble calcium is not incorporated in non-European regulation.
As far as the nutrients water soluble calcium and magnesium, total sulfur and water soluble sulfur are
concerned, a more in depth statistical evaluation has been made revealing that there are still conflicts
between the analytical results and the official tolerances.
Nonetheless, based on the refined data population and the back calculation of reasonable tolerances, it is
recommended to introduce the following adjustments to the officially applied tolerance limits:
Sulfur (total and water soluble): 1,2 to 1,5;
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Calcium and Magnesium (water soluble): 1,2 to 1,5.
Although the proposal above is an improvement to the existing situation, and given the inherent problems of
the method of analysis and certain matrices, the proposed tolerance still does not cover completely the
variability originating from sampling, manufacturing and analysis. Nevertheless, considering the cross-check
with the field data, the proposed tolerance levels should be capable to take into account the full variability.
The proposed adjustment to the calcium tolerance still reveals possible conflicts for products with high calcium
content, i.e. CAN 27.
Method 2.6.2 (EN 15750) for the determination of different forms of nitrogen in fertilizers containing nitrogen
only as nitric, ammoniacal and urea nitrogen, such as UAN + S, does not perform well enough. Therefore, two
alternative methods have been tested and have been proposed to replace method 2.6.2. It is also
recommended to adjust the existing tolerance levels from 0,6 % up to 1,0 %.
However, an extra option could be to consider some further evaluation and development work regarding an
alternative method for determination of the concerned nutrients, i.e. water soluble sulfur, calcium and
magnesium. The nature of this work would be more in the field of method development at first instance,
whereas a next step would be the launch of a ring test to define its precision data. Based on the evaluation of
its statistical data, it should be possible to judge whether the alternative method is suitable for integration in
the EU regulatory frame.
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Annex A
(informative)
Statistical data of the inter-laboratory tests and findings
A.1 General
Tables A.1 to A.32 show the accuracy data compared to tolerances for the methods given in Annex IV of the
Regulation (EC) No. 2003/2003,
where
x
is the mean value (mass fraction);
s is the repeatability standard deviation (mass fraction);
r
RSD is the relative repeatability standard deviation;
r
r is the repeatability limit (mass fraction);
s is the reproducibility standard deviation (mass fraction);
R
RSD is the relative reproducibility standard deviation;
R
R is the reproducibility limit (mass fraction).
A.2 Nitrogen
Table A.1 — Determination of ammoniacal nitrogen (EC method 2.1, EN 15475)
Sample Sample Number Number of Current
type of labs labs retained EC
after x s RSD r s RSD R Tole-
r R R
r
elimination of rance
outliers
AN 33,5 Solid 22 18 16,67 0,05 0,29 0,13 0,23 1,36 0,63 0,6
CAN 27 Solid 24 24 13,53 0,05 0,36 0,14 0,14 1,02 0,39 0,8
NPK1 Solid 24 23 8,38 0,03 0,38 0,09 0,12 1,43 0,34 1,1
(14-8-24+8S)
NPK2 Solid 24 21 10,02 0,03 0,28 0,08 0,16 1,59 0,45 1,1
(16-16-8+4S)
NP (DAP) Solid 24 21 17,64 0,04 0,20 0,10 0,23 1,31 0,65 1,1
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Table A.2 — Determination of nitric and ammoniacal nitrogen according to Devarda
(EC method 2.2.3; EN 15476)
Sample Sample Number Number of Current
type of labs labs retained EC Tole-
RSD
after x s RSD r s R rance
r r R
R
elimination of
outliers
AN 33.5 Solid 21 18 33,45 0,04 0,13 0,12 0,28 0,83 0,77 0,6
CAN 27 Solid 19 16 26,97 0,06 0,23 0,17 0,22 0,80 0,60 0,8
NPK1 Solid 23 22 14,14 0,04 0,31 0,12 0,22 1,58 0,63 1,1
(14-8-24+8S)
NPK2 Solid 23 21 16,04 0,04 0,23 0,10 0,21 1,33 0,60 1,1
(16-16-8+4S)
NP (DAP) Solid 21 19 17,70 0,05 0,30 0,15 0,18 1,03 0,51 1,1
Table A.3 — Determination of total nitrogen in urea (EC method 2.3.3; EN 15478)
Sample Sample Number Number of Current
type of labs labs retained EC Tole-
x s RSD r s RSD R
after rance
r r R R
elimination of
outliers
Urea Solid 19 16 46,26 0,11 0,3 0,24 0,27 0,57 0,74 0,4
Table A.4 — Spectrophotometric determination of biuret in urea (EC method 2.5, EN 15479)
Sample Sample Number Number of Current
type of labs labs retained EC
after x s RSD r s RSD R Reg.
r r R R
elimination of
outliers
Urea Solid 13 11 0,81 0,01 1,7 0,04 0,07 8,9 0,20 Max 1,2
Urea + S Solid 9 6 0,76 0,02 2,0 0,05 0,14 18,0 0,38 Max 0,9
Table A.5 — Determination of different forms of nitrogen in fertilizers containing nitrogen only as
nitric, ammoniacal and urea nitrogen (EC method 2.6.2, EN 15750)
Sample Sample Number Number of labs Current
type of labs retained after RSD EC
x s RSD r s R
r r R
elimination of Tole-
R
outliers rance
UAN+S Liquid 11 9 22,76 0,16 0,7 0,45 1,23 5,4 3,45 0,6
UAN+S Liquid 7 7 22,2 0,2 0,9 0,6 1,5 6,9 4,3 0,6
(repetition)
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SIST-TS CEN/TS 16490:2013
CEN/TS 16490:2013 (E)
Table A.6 — Determination of different forms of nitrogen in fertilizers containing nitrogen only as
nitric, ammoniacal and urea nitrogen (EC method ISO 5315) (new samples)
Sample Sample Number Number of Current
type of labs labs retained EC
x s RSD r s RSD R
after Toler-
r r R R
elimination of ance
outliers
UAN+S Liquid 12 12 22,01 0,10 0,5 0,29 0,56 2,5 1,55 0,6
Table A.7 — Determination of different forms of Nitrogen in fertilizers containing nitrogen only as
nitric, ammoniacal and Urea nitrogen (“German method using Iron and tin chloride as reducing
agent”) (new samples)
Sample Sample Number Number of Current
type of labs labs retained EC
after x s RSD r s RSD R Tole-
r r R R
elimination of rance
outliers
UAN+S Liquid 7 7 21,88 0,10 0,4 0,27 0,47 2,2 1,32 0,6
Findings:
EC method 2.1:
Based on the statistics above, there can be concluded that Method 2.1 performs well, under repeatability
as well as reproducibility conditions.
Considering the statistical data, the definition of the reproducibility limit, as well as the tolerances
mentioned in Annex II of EC Regulations 2003/2003 it can be concluded that, despite the good results,
difficulties occur for ammonium nitrate with more than 32 % N. The value of R already exceeds the
allowed tolerance of 0,6 % for ammonium nitrate with more than 32 % N (Annex II of Regulation (EC)
No. 2003/2003), whereas this tolerance should cover variations in manufacturing, sampling and analysis.
EC method 2.2.3:
Based on the statistics above, there can be concluded that Method 2.2.3 performs well, under
repeatability as well as reproducibility conditions.
Considering the statistical data, the definition of the reproducibility limit, as well as the tolerances
mentioned in Annex II of Regulation (EC) No. 2003/2003 it can be concluded that, despite the good
results, difficulties occur for ammonium nitrate with more than 32 % N. The value of R already exceeds
the allowed tolerance of 0,6 % for ammonium nitrate with more than 32 % N (Annex II of
Regulation (EC) No. 2003/2003), whereas this tolerance should cover variations in manufacturing,
sampling and analysis as well. Also for ammonium nitrate with le
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