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- Practical Guide -
Page 88 of 153
Annex B: Guidance for establishing an experimental relationship between the quantity
(Q) of a substance in the finished material or article and its specific
migration (SM)
Preface:
The aim of this document is to give an answer to the following question:
How can industry and the enforcement laboratories confirm compliance with an SML
through the verification of compliance with the corresponding maximum initial quantity in
the plastic using an experimental procedure?
1. Introduction
The experimental determination of the specific migration into food(simulants) requires a
considerable amount of time and cost and is even in many cases impossible due to
technical/analytical problems, chemical degradation/volatilisation of the migrant or non-
availability of corresponding analytical methods. From this it is obvious, that correlating
SML restrictions with maximum initial concentration in a polymer (MIC) would not only be
of great help but can also be considered to be a very economical alternative procedure to
migration or compliance testing.
If for one given polymer type the basic Q/SM relationship (i.e. the basic diffusivity behaviour
of this material) has been established using one or more typical migrants, then application of
the migration/diffusion model (see Annex I) is possible to establish any specific MIC/SML
relationship without further experimental migration testing within a (previously) well
established and defined application range.
One of the foreseeable advantages of migration modelling is that it will allow high speed
computer-assisted migrational access to any foodstuff matrix independent of its analytically
limiting compositional complexity and manage any given individual food packaging system
(geometry, ratio mass/contact area, shelf life etc.). Moreover, migration modelling is
completely 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 height of obtained migration results
but also for identification of otherwise hardly detectable false-negative test results.
2. Scope
This method describes how to measure and derive experimentally/theoretically the basic
diffusivity behaviour (A
P
value, see below) of a given test plastics material using one or more
selected test migrants only. Based on the determined A
P
value, Q/SM or MIC/SML
relationships can be calculated for any other migrant in dependency of its molecular weight
and for the applicable temperature range.
3. General technical considerations
3.1
Test material