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- Practical Guide -
Page 62 of 153
insensitive to chemical degradation and reactivity or physical volatilisation of test migrants
as occuring in real migration testing. It can therefore not only be used for plausability
considerations with respect to the extent and amplitude of obtained migration results but also
for identification of otherwise hardly detectable false-negative test results. Consequently,
migration modelling offers not only a very economic approach for industry for taking quick
decisions in relation to packaging development and design but also to surveillance
laboratories who have quick and may be unique access to otherwise inaccessible migrational
evaluation informations. The conclusions of the thematic network take into account both
industrial and legal requirements as well as scientific considerations.
The aim of this document is to describe the results on an upperbound migration prediction
as an outcome from the above mentioned EU project and to assist the possible users of the
described model by providing sufficient explanatory guidance, tables, practical examples and
an experimental procedure for verification purposes
. According to the current state-of-the-
art, the scope and applicability of migration prediction comprises the mass transfer of
migrants listed in Annex A and other organic substances from packaging polymers
mentioned in this report when in contact with food simulants according to Directive
97/48/EU. The above list is derived from reference /13/.
However, it should be noted that the procedure described in Annex B offers a possibility to
expand the scope also to other polymers or polymer modifications.
Further reading can be found in the bibliographic references.
2
Migration modelling
Currently existing predictive mathematical models for migration estimation are essentially
based on diffusion theory and consideration of partitioning effects. The underlying key
parameters are the diffusion coefficient of the migrant in the plastic D
P
as well as the
partition coefficient of the migrant between the plastic and the food (simulant) K
P,F
.
Although these models are still under further scientific discussion, refinement or
development, they provide an estimation of worse case migration scenarios for monolayer,
homogeneous materials, and without any modification in time and interaction with food. One
of these models has been used in an approach to predict upperbound migration values, which
has been validated within the EU project SMT-CT98-7513 /1, 2/. It is based on some general
requirements (see 2.1) and is designed such that it enables migration prediction with
sufficient safety margins.
A list of chemical substances, which includes monomers and other starting substances as well
as additives from the European positive list for plastics intended to come into contact with
foodstuffs is given in Annex A of this report /13/.