SIST-TP CEN/TR 16364:2012
(Main)Influence of materials on water intended for human consumption - Influence due to migration - Prediction of migration from organic materials using mathematical modelling
Influence of materials on water intended for human consumption - Influence due to migration - Prediction of migration from organic materials using mathematical modelling
This Technical Report describes a procedure, based on a diffusion model, to be applied to the estimation of specific migration of substances into drinking water from organic materials intended to come into contact with drinking water. The modelling approach is readily applicable to certain organic materials, as explained in this report. In principle, the diffusion modelling approach is applicable to other organic materials but practical difficulties, in relation to obtaining data to feed into the diffusion model, may restrict or prevent its application. Accordingly, in addition to the diffusion model, scientific estimation procedures for the required data inputs need to be considered. The approach is normally applicable to organic substances that are soluble in the material matrix. Substances applied externally to a product made of an organic material, e.g. antistatic agents, lubricants, etc. are excluded from the diffusion modelling approach, as are electrolytes, salts, oxides and metals. Only organic substances with well-defined molecular weight or mixtures with well-defined ranges of molecular weights are amenable to the diffusion modelling approach. The diffusion modelling approach is readily applicable to amenable organic materials in the form of a pipe or a sheet, where data such as material thickness is readily calculable. More complicated product shapes, such as fittings, require assumptions to be made. It may not be possible to model the effects of test waters that are chemically active, for example test waters to which chlorine has been added to simulate chlorinated drinking water. This is because substances that migrate from a material into water containing chlorine can be converted by chemical reaction into substances with different properties.
Einfluss von Materialien auf Wasser für den menschlichen Gebrauch - Einfluss infolge der Migration - Abschätzung der Migration aus organischen Materialien mittels mathematischer Modellierung
Dieser Technische Bericht beschreibt ein Verfahren auf der Grundlage eines Diffusionsmodells, das für die Abschätzung der spezifischen Migration von Substanzen in Trinkwasser aus organischen Materialien für den Kontakt mit Trinkwasser verwendet wird.
Das Modellierungsverfahren ist einfach für bestimmte organische Materialien anwendbar, wie in diesem Bericht erläutert. Grundsätzlich ist die Verfahrensweise der Diffusionsmodellierung auf andere organische Materialien anwend¬bar, allerdings können praktische Probleme in Zusammenhang mit der Erhebung der Eingabedaten für das Diffusions¬modell ihre Anwendung einschränken oder verhindern. Dementsprechend müssen zusätz¬lich zum Diffusions¬modell wissenschaftliche Abschätzungsverfahren für die erforderlichen Eingabedaten erwogen werden.
Die Verfahrensweise ist gewöhnlich für organische Substanzen anwendbar, die in der Materialmatrix löslich sind. Substanzen, die von außen auf ein Produkt aus einem organischen Material aufgebracht werden, z. B. Antistatik¬mittel, Schmiermittel usw., sind von der Diffusionsmodellierung ebenso ausgeschlossen wie Elektrolyte, Salze, Oxide und Metalle. Ausschließlich organische Substanzen mit einer genau bestimmten Molekularmasse oder Gemische mit genau bestimmten Bereichen von Molekularmassen sind für die Diffusionsmodellierung geeignet.
Die Verfahrensweise der Diffusionsmodellierung ist einfach anzuwenden für geeignete organische Materialien in Rohr- oder Plattenform, für die Daten, wie z. B. Materialdicke, einfach zu berechnen sind. Bei komplizier-teren Produktformen, wie z. B. bei Formstücken, sind Annahmen erforderlich.
Die Modellierung der Einflüsse von chemisch aktivem Versuchswasser, z. B. Versuchswasser, dem Chlor zuge¬setzt wurde, um chloriertes Trinkwasser zu simulieren, ist möglicherweise nicht durchführbar. Dies ist darin begründet, dass Substanzen, die aus einem Material in chloriertes Wasser migrieren, durch chemische Reak¬tion in Substanzen mit veränderten Eigenschaften umgewandelt werden können.
Influence des matériaux sur l'eau destinée à la consommation humaine - Influence de la migration - Utilisation de modèles mathématiques pour prévoir la migration depuis des matériaux organiques
Le présent Rapport technique décrit un mode opératoire s’appuyant sur un modèle de diffusion, à appliquer
afin d’estimer le niveau de migration spécifique de substances vers l’eau potable, depuis des matériaux
organiques destinés à entrer en contact avec l’eau potable.
L’approche par modélisation est facilement applicable à certains matériaux organiques, comme expliqué dans
le présent rapport. En principe, l’approche par modèles de diffusion peut être utilisée avec d’autres matériaux
organiques, mais des difficultés d’ordre pratique, liées à l’obtention des données destinées à alimenter le
modèle de diffusion, peuvent limiter ou empêcher son utilisation. En conséquence, outre le modèle de
diffusion, des modes opératoires permettant une estimation scientifique des données de départ requises
doivent être envisagés.
L’approche est normalement applicable aux substances organiques solubles dans la matrice du matériau. Les
substances appliquées de manière externe à un produit composé d’un matériau organique, par exemple,
agents antistatiques, lubrifiants, etc., sont exclus de l’approche par modèles de diffusion, tout comme les
électrolytes, sels, oxydes et métaux. Seules des substances organiques de masse moléculaire bien définie ou
des mélanges dont les plages de masses moléculaires sont bien définies sont compatibles avec l’approche
par modèles de diffusion.
L’approche par modèles de diffusion est facilement applicable aux matériaux organiques compatibles se
présentant sous la forme d’un tuyau ou d’une feuille, c’est-à-dire ceux pour lesquels on peut aisément calculer
des données telles que l’épaisseur. Les formes de produits plus complexes, telles que les raccords,
nécessitent de poser des hypothèses.
Il peut s’avérer impossible de modéliser les effets d’eaux d’essai chimiquement actives, par exemple des eaux
d’essai auxquelles on a ajouté du chlore afin de simuler une eau potable chlorée. En effet, des substances
migrant d’un matériau vers une eau contenant du chlore peuvent être transformées par réaction chimique en
substances possédant des propriétés différentes.
Vpliv materiala na pitno vodo - Vpliv migracije - Ocenjevanje migracije iz organskih snovi z uporabo matematičnega modeliranja
To tehnično poročilo navaja postopek na osnovi difuzijskega modela, ki se uporablja za oceno posebne migracije materiala iz organskih snovi, namenjenih za stik s pitno vodo, v pitno vodo. Pristop z modeliranjem se uporablja za nekatere organske snovi, kot je pojasnjeno v tem poročilu. Pristop difuzijskega modeliranja se načeloma uporablja za druge organske snovi, vendar lahko težave v praksi, povezane s pridobivanjem podatkov za vnos v difuzijski model, omejijo ali preprečijo njegovo uporabo. Glede na to je treba poleg difuzijskega modela obravnavati postopke znanstvene ocene za zahtevani vnos podatkov. Pristop se običajno uporablja za organske snovi, ki so topne v matriki materiala. Snovi, kot so elektroliti, soli, oksidi in kovine, ki se na proizvod iz organske snovi, npr. antistatična sredstva, maziva itd., nanesejo od zunaj, so izključene iz pristopa z difuzijskim modeliranjem. Za pristop z difuzijskim modeliranjem so primerne le organske snovi z dobro opredeljeno molekulsko maso ali mešanice z dobro opredeljenimi območji molekulske mase. Pristop z difuzijskim modeliranjem se uporablja za primerne organske snovi v obliki cevi ali plošč, za katere je mogoče izračunati debelino materiala. Pri bolj zapletenih oblikah, kot so armature, so potrebne predpostavke. Morda ne bo možno modelirati učinkov preskusnih vod, ki so kemično aktivne, na primer preskusnih vod, ki jim je bil z namenom simuliranja klorirane pitne vode dodan klor. Razlog za to je dejstvo, da je mogoče snovi, ki migrirajo iz materiala v vodo, ki vsebuje klor, s kemijsko reakcijo pretvoriti v snovi z drugačnimi značilnostmi.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 16364:2012
01-september-2012
9SOLYPDWHULDODQDSLWQRYRGR9SOLYPLJUDFLMH2FHQMHYDQMHPLJUDFLMHL]RUJDQVNLK
VQRYL]XSRUDERPDWHPDWLþQHJDPRGHOLUDQMD
Influence of materials on water intended for human consumption - Influence due to
migration - Prediction of migration from organic materials using mathematical modelling
Einfluss von Materialien auf Wasser für den menschlichen Gebrauch - Einfluss infolge
der Migration - Abschätzung der Migration aus organischen Materialien mittels
mathematischer Modellierung
Influence des matériaux sur l'eau destinée à la consommation humaine - Influence de la
migration - Utilisation de modèles mathématiques pour prévoir la migration depuis des
matériaux organiques
Ta slovenski standard je istoveten z: CEN/TR 16364:2012
ICS:
13.060.20 Pitna voda Drinking water
67.250 Materiali in predmeti v stiku z Materials and articles in
živili contact with foodstuffs
SIST-TP CEN/TR 16364:2012 en,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TP CEN/TR 16364:2012
TECHNICAL REPORT
CEN/TR 16364
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
June 2012
ICS 13.060.20
English Version
Influence of materials on water intended for human consumption
- Influence due to migration - Prediction of migration from
organic materials using mathematical modelling
Influence des matériaux sur l'eau destinée à la Einfluss von Materialien auf Wasser für den menschlichen
consommation humaine - Influence de la migration - Gebrauch - Einfluss infolge der Migration - Abschätzung
Utilisation de modèles mathématiques pour prévoir la der Migration aus organischen Materialien mittels
migration depuis des matériaux organiques mathematischer Modellierung
This Technical Report was approved by CEN on 9 April 2012. It has been drawn up by the Technical Committee CEN/TC 164.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, 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
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16364:2012: E
worldwide for CEN national Members.
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Contents Page
Foreword .4
Introduction .5
1 Scope .7
2 Normative references .7
3 Terms and definitions .7
4 Principle .9
5 Apparatus .9
6 Assumptions that need to be valid .9
7 Required data inputs . 10
7.1 General . 10
7.2 Diffusion coefficient of the substance (D ) . 10
P
7.3 Partition coefficient of the substance (K ). . 10
P,W
7.4 Temperature of the system (T) . 11
7.5 Geometry of the material . 11
7.6 Material thickness, (d ). 11
P
7.7 Initial concentration of the substance in the material (c ) . 11
P,0
7.8 Chemical identity of the substance and its relative molecular weight . 11
7.9 Specific gravity of the material (ρρρρ ) . 11
P
7.10 Simulation of contact of organic material with test water . 11
8 Procedure . 11
9 Expression of results . 12
10 Report . 12
Annex A (informative) Principles of the modelling approach . 14
A.1 Migration modelling . 14
A.2 Initial and boundary conditions . 14
A.3 Solution of the diffusion equation . 15
A.4 Obtaining and using diffusion coefficients . 15
A.4.1 Diffusion coefficients from literature . 15
A.4.2 Diffusion coefficients from experiment . 16
A.4.3 Estimation of diffusion coefficients . 16
A.4.4 Upper-limit diffusion coefficient . 17
A.4.5 Validated AP', AP'* and ττττ values . 18
A.4.6 Diffusion coefficients for other materials . 18
A.4.7 Worst-case diffusion coefficients . 19
A.5 Obtaining and using partition coefficients . 19
A.5.1 General . 19
A.5.2 Partition coefficients from literature and from experiment . 19
A.5.3 Partition coefficients from experiment . 20
A.5.4 Estimation of partition coefficients. 20
A.5.5 Worst-case partition coefficients . 21
Annex B (informative) Examples of the application of modelling to migration of substances from
a material into drinking water . 22
B.1 Introduction . 22
B.2 Contact conditions . 22
B.3 Example calculations . 22
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B.3.1 General . 22
B.3.2 Example 1, cold water test with the material constant in accordance to [7] . 23
B.3.3 Example 2 Cold water test with “realistic” material constants (experimentally measured) . 24
Annex C (informative) Validation of the numerical algorithm and software tools . 26
C.1 General . 26
C.2 Example A . 27
C.3 Example B . 28
Bibliography . 32
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Foreword
This document (CEN/TR 16364:2012) has been prepared by Technical Committee CEN/TC 164 “Water
supply”, the secretariat of which is held by AFNOR.
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.
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Introduction
During the last two decades, several scientific investigations have demonstrated that migration from organic
materials into liquid simulants is a physical process that can be modelled successfully. Mass transfer from an
organic material into a liquid simulant is predictable because in many cases it follows Fick´s law of diffusion,
i.e. the diffusion process is the rate determining step. To predict migration from organic materials into
contacting media a corresponding diffusion model was established.
This Technical Report describes the application of predictive diffusion modelling to the estimation of the
migration of a substance from a product intended for contact with water intended for human consumption – for
convenience, and where appropriate, referred to as drinking water in this report. The application applies to
organic materials, such as polymers, used to make such products.
The purpose of the report is to stimulate the use of such techniques in member states such that sufficient
experience is generated to enable the value of such modelling to be assessed in relation to complementing or
substituting the conventional approach.
Normally in member states the estimation of such migration is performed by standardised procedures based
on laboratory testing and analysis, i.e. an experimental approach. Migration modelling is an alternative to this
type of experimental testing. The experimental determination of the specific migration of substances into test
water (simulated drinking water) often requires a considerable amount of time and it can be costly. This
conventional approach has worked well and, of course, it generates data on the actual concentration of a
substance in test water. However, in some cases the analysis is difficult or even impossible due to problems
caused, for example, by chemical degradation, volatilisation of the substance. In addition, the substance may
not be amenable to, or the target concentration of interest may be too low for, available analytical techniques
Therefore, the application of a mathematical model could have considerable benefits for industry and
regulators, as experience has shown in the control of migration from plastic materials in contact with
foodstuffs.
Thus, the modelling approach is attractive because, in principle, it is quicker and more flexible than the
conventional testing approach, in that different exposure conditions can be readily investigated - and it should
be cheaper.
Modelling of migration has been used for several years in the United States as an additional tool in support of
regulatory decisions. Also, the European Union has introduced such diffusion modelling by means of
th
EU Directive 2001/62/EC (the 6 amendment of Directive 90/128/EEC), consolidated in Directive 2002/72/EC
as a compliance and quality assurance tool for plastic materials intended to come in contact with foodstuff [3].
The European project SMT-CT98-7513, Evaluation of Migration Models in Support of Directive 90/128/EEC,
successfully demonstrated the practical value of such diffusion models. The main objectives of this project
were to demonstrate:
the validity of migration models for compliance purposes;
that a relationship between the specific migration limit (SML) and the concentration of a substance in the
finished product can be established.
A report of this project has been finalised and the project results were published in a scientific journal [4]. As
indicated above, a major advantage of migration modelling is that it enables calculation of migration values
independent of the limitations that affect the experimental/analytical approach. For example, at low cost one
can quickly investigate, for compliance or research purposes, a wide range of conditions of contact between
material with test water.
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The diffusion modelling approach described was originally developed for, and accepted by, the European
Commission in the area of plastic materials in contact with foodstuffs. It has been successfully used to
simulate the conventional experimental/analytical approach to compliance testing of plastics in contact with
foodstuffs. In this latter approach different liquid food simulants, including aqueous simulants, are used.
In principle, the approach is applicable to many organic materials. However, today it has been applied mainly
to different types of polyethene, polypropene, polystyrene and polyvinyl chloride.
Like the experimental approach, the mathematical approach has its limitations. An accurate prediction of the
migration of a substance from an organic material to water requires detailed knowledge of the diffusion
behaviour of the materials and substances under investigation. The level of information may well require
extensive experimental studies – more than the experimental, analytical approach would require. An important
feature of the mathematical approach is the possibility of generalisation. Based on known average diffusion
behaviour of polymers and substances, a maximum or 'upper-limit' migration can be calculated. This so-called
'worst-case' result may then be used for compliance purposes.
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1 Scope
This Technical Report describes a procedure, based on a diffusion model, to be applied to the estimation of
specific migration of substances into drinking water from organic materials intended to come into contact with
drinking water.
The modelling approach is readily applicable to certain organic materials, as explained in this report. In
principle, the diffusion modelling approach is applicable to other organic materials but practical difficulties, in
relation to obtaining data to feed into the diffusion model, may restrict or prevent its application. Accordingly, in
addition to the diffusion model, scientific estimation procedures for the required data inputs need to be
considered.
The approach is normally applicable to organic substances that are soluble in the material matrix. Substances
applied externally to a product made of an organic material, e.g. antistatic agents, lubricants, etc. are excluded
from the diffusion modelling approach, as are electrolytes, salts, oxides and metals. Only organic substances
with well-defined molecular weight or mixtures with well-defined ranges of molecular weights are amenable to
the diffusion modelling approach.
The diffusion modelling approach is readily applicable to amenable organic materials in the form of a pipe or a
sheet, where data such as material thickness is readily calculable. More complicated product shapes, such as
fittings, require assumptions to be made.
It may not be possible to model the effects of test waters that are chemically active, for example test waters to
which chlorine has been added to simulate chlorinated drinking water. This is because substances that
migrate from a material into water containing chlorine can be converted by chemical reaction into substances
with different properties.
2 Normative references
Not applicable.
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
diffusion model
Fick's Second Law of diffusion that simulates the diffusion of substances from a material into drinking water
3.2
experimental test
technical operation that consists of the determination of one or more characteristics of a given product
3.3
experimental testing procedure
set of instructions for determining by experiment the migration of a substance from a material into water
3.4
software tool
set of instructions for a computer (e.g. a computer program)
Note1 to entry: In this document it refers to instructions designed to model migration of substances from a material
into water.
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3.5
product
manufactured item intended for contact with drinking water
3.6
monolayer
product this is or contains a material that consists of one layer
3.7
multilayer
product this is or contains a material that consists of more than one layer
3.8
migration
movement of a substance or substances from one compartment (a material) into a second compartment
(water)
3.9
migration period
period of time in which the migration is carried out under specified conditions
3.10
migration rate
mass of a measured substance or substances migrating from the surface of a test piece into the test water in
one day
3.11
substance
chemical that is a constituent of a material used in contact with drinking water with the potential to migrate into
drinking water
3.12
contact area
surface area of a material in contact with a specific volume of water
3.13
volume to area ratio
ratio of the volume of water in contact with a specific area of material
3.14
test water
water used for migration testing
3.15
diffusion equation
partial differential equation known as Fick's Second Law that describes the variation of the concentration of a
substance in a system (e.g. a polymer in contact with water) depending on time and location
3.16
diffusion coefficient
factor of proportionality representing the amount of substance diffusing across a unit area through a unit
concentration gradient in unit time (e.g. from polymer to water)
3.17
molecular weight
mass of one mole of molecules calculated using standard atomic weights, expressed as g/mol
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3.18
partition coefficient
ratio of the concentrations, at equilibrium, of a substance in the two phases of a mixture of two immiscible
solvents
Note1 to entry: Examples are polymer and water or in the case of the Octanol-Water Partition Coefficient, 1-octanol
and water.
4 Principle
Current predictive mathematical models for the estimation of migration of a substance from an organic
material into another medium, such as a food simulant or drinking water, are based on diffusion theory and
partitioning effects. Various parameters and information are needed to make the diffusion model work, in
terms of calculating the concentration of a substance in test water or a migration rate.
Various assumptions need to be valid for the model to work satisfactorily.
If the described data inputs are available, or can be estimated, and the various assumptions valid, then the
model can be used to estimate reliably the concentration of a substance in water after a specific time of
contact between an organic material and water - and at a specific temperature. If required this concentration
can be used to calculate a migration rate.
Depending on how the various data inputs are obtained, or used, the diffusion model can be used to estimate
a worst-case value of migration, i.e. to produce a value that is likely to be higher than a value estimated by
means of the conventional experimental/analytical approach.
The diffusion model can be used in a manner that simulates the conditions applied in the conventional
analytical approach used in member states.
Annex A provides detail on the principles on which the diffusion modelling approach is based.
5 Apparatus
In order to predict migration a personal computer set-up capable of running an appropriate validated software
tool is required. See Annex C for information on validation of the numerical algorithm and the software.
Currently suitable software to run the diffusion model is available.
6 Assumptions that need to be valid
The diffusion model is based on the following assumptions being valid:
1) the migration process of the substance within organic materials shall obey the law of diffusion (Fick’s
Second Law);
2) the migrant is an uncharged, organic substance;
3) the mass of the substance in the system is conserved, i.e. no substance is consumed or built up;
4) the initial concentration of the substance in the material shall be homogeneous, i.e. it does not vary
significantly and is constant, i.e. is non-degradable by chemical reaction; this applies to each layer in
the case of multilayer products;
5) the material thickness shall be uniform (i.e. it does not vary significantly);
6) the volume of the organic material and the water is finite;
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7) there shall be no boundary resistance for the transfer of the substance between the organic material
and water;
8) the uptake of the substance by the water shall be fast, i.e. the water is a high diffusivity medium or
well-mixed liquid;
9) the interaction between the organic material and water shall be negligible such that no swelling of
organic material by uptake of water occurs during the migration process.
7 Required data inputs
7.1 General
The data inputs required to use the diffusion model are described in 7.2 to 7.10.
7.2 Diffusion coefficient of the substance (D )
P
The diffusion coefficient is a parameter dependant on the properties of the substance and of the organic
material. It relates to the mobility of the substance in the organic material. It may be obtained in several ways:
a) from tables;
b) determined by experiment [5];
c) estimated by a validated scientific estimation procedure:
1) Arrhenius equation [6];
2) estimation procedure developed by Piringer validated in the EU Project SMT-CT98-7513 [4]; the
diffusion coefficients for various organic materials can be estimated from their polymer-specific
parameter, A [7];
P
d) assumed to be a worst-case value.
A detailed explanation on how to obtain and use diffusion coefficients, see A.4.
7.3 Partition coefficient of the substance (K ).
P,W
The partition coefficient K is a parameter dependant on the relative solubility of the substance in relation to
P,W
the organic material and the water. It relates to what extent the substance moves from the organic material
into water at thermodynamic equilibrium. It may be obtained in several ways:
a) from tables;
b) determined by experiment;
c) estimated by a validated scientific estimation procedure;
1) estimation from the solubility of the substance in water, i.e. the concentration in the water will not
exceed its water solubility (worst-case assumption) [8];
2) estimated from the octanol/water partition coefficient of the substance [9,10];
d) assumed to be a worst-case value.
A detailed explanation on how to obtain and use partition coefficients, see A.5.
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7.4 Temperature of the system (T)
In many cases the temperature of the system (material and test water) to be modelled will be specified in the
relevant regulations or standard. For example, in EN 12873-1, the temperature for ‘cold’ water simulation is
23 °C.
7.5 Geometry of the material
The surface area of the material (S) and the amount of test water (V ) in contact with the material shall be
DW
known. In the case of organic materials in the form of sheets or piping (cylinders) these values are readily
calculable. More complex product forms may require assumptions and approximations to be made. These
should be noted in the report (see Clause 10).
7.6 Material thickness, (d )
P
Evidence is needed, or an assumption shall be made, that the thickness does not vary significantly.
7.7 Initial concentration of the substance in the material (c )
P,0
This is important because it has a prime influence on the magnitude of the predicted level of migration. It may
be obtained by:
determination (analysis of the substances in the organic material – the feasibility of this will depend on the
specific substance/material combination);
based on the amount added during the production of the material; this applies readily to additives but not,
of course, monomers and other reactive starting substances.
7.8 Chemical identity of the substance and its relative molecular weight
The exact chemical identity (not commercial names) of the substance and its relative molecular weight (M ) in
r
g/mol are required.
7.9 Specific gravity of the material (ρρρρ )
P
The specific gravity of the material is required.
7.10 Simulation of contact of organic material with test water
The diffusion modelling process simulates the conditions of contact of the organic material with test water. The
contact may relate to:
duration of the contact of the sample of organic material with water during pre-washing and conditioning
(t ) in s;
s
duration of the contact of the sample of organic material with test water during migration test (t ) in s;
n
number of migration test cycles, the successive periods of contact of the sample of organic material with
test water (N).
8 Procedure
The exact procedure will depend on the software used and its ‘user-friendliness’.
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SIST-TP CEN/TR 16364:2012
CEN/TR 16364:2012 (E)
In principle, migration models can be used to complement or substitute conventional experimental testing in
member state approval schemes for products intended for contact with drinking water. At present member
states use different approval schemes. However, it is possible at some point in future many, or all, member
states will adopt EN 12873-1 and -2.
It can be applied assuming conditions of contact between material and test water that constitutes a worst-case
situation (i.e. unlikely in practice) that would lead to enhanced migration. Additionally, worst-case values for
diffusion and partition coefficients could be used. This would provide safety factors in that, if a satisfactory (in
relation to not exceeding a corresponding limit value) migration value were obtained, then one could be
satisfied that conventional testing would show the organic material to be satisfactory.
Annex B gives examples of the application of the diffusion modelling approach to assessments as described
above.
9 Expression of results
The result of a prediction based on the migration models can be expressed in several ways. This depends on
the software tool used and the objective of the c
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