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- Practical Guide -
Page 76 of 153
In conformity with Article 4 (b) in Directive 2002/72/EC, the specific limits expressed in
mg/kg shall be divided by the conventional conversion factor of 6 in order to express them in
mg/dm
2
. For the above additive (Irganox 1076) the specific limit is now 6/6 = 1 mg/dm
2
<
2.8 mg/dm
2
. The sandwiches with fatty substances on the surface belong to the category of
food with the reference number 08.08 in the Directive 85/572/EEC and the reduction factor
X/5 can be used. This means in the above example: (m
F,t
/A)/5 = 0.56 < 1 mg/dm
2
and,
consequently, it is in compliance with the Directive 2002/72/EC.
For the second additive, Irgafos 168 (PM/REF = 74240), with the molecular weight M
r
= 647
a smaller migration rate results (Eq.2) as for Irganox 1076 with M
r
= 531. With the tenfold
higher migration limit (SML = 60 mg/kg) no further investigation of the specific migration is
necessary.
Example 2:
A film of LDPE (100
mm) is used in the same way as in example 1 but the origin of the
plastic is unknown.
Which informations can be obtained from mathematical modelling about the specific
migration of any additives possibly contained in the film?
From the previous example we know that a reduction factor X/5 can be used. That means the
film is in compliance with the Directive 2002/72/EC if (m
F,t
/A)/5
SML/6 = 1 mg/dm
2
because for most additives in table 4 the specific migration limits are SML
6 mg/kg. Let us
start with the additive with the smallest molecular weight, Mr
i
= 214 and SML = 6. As in the
first example an initial concentration of 0.5% (5000 mg/kg) is assumed as an upper limit.
Modelling with the software:
...can be done with the aid of the previous File Ex1 (saved under Example1) and requires to
provide the following informations:
1.
Information about the migrateable substance
user defined migrateable substance
molecular weight (214)
OK
Calculation of migration:
Estimation TDM TDM + E1.
Result: m
F,t
/A = 4.7 mg/dm
2
.
Discussion of the result:
With the reduction factor X/5 the final result is (m
F,t
/A)/5 = 0.94 < 1 mg/dm
2
.
Consequently, for all additives in table 4.2.1 with M
r
> 214 and SML
6 the film can
be considered to be in compliance with the Directive 2002/72/EC because the
migration decreases with increasing M
r
.
By repeating the calculations in the same manner for the remaining additives in table
4.2.1 the estimated migration values exceed the corresponding SML values for 5
additives with the following PM/REF: 38560, 38820, 46640, 60320, 95270.
If one decides to extract all the migrants from the LDPE film using an adequate
method, e.g. hot toluene for solving and methanol for re-precipitation, then a quick
semi-quantitative analysis is sufficient for a decision of necessary further investigation.