BS 1186-11:2002 pdf download – Materials and articles in contact with foodstuffs — Plastics — Part 11: Test methods for overall migration into mixtures of C-labelled synthetic triglycerides
Test specimens of known mass are immersed in a mixture of 1 4 C-labelled synthetic triglycerides for the exposure time at temperatures above 20 °C and, up to and including, 1 21 °C, then taken from the mixture of 1 4 C-labelled synthetic triglycerides, blotted to remove synthetic triglycerides adhering to the surface and reweighed. The specimens will usually retain absorbed mixture of 1 4 C-labelled synthetic triglycerides which are extracted and determined quantitatively by means of liquid scintillation counting. For some plastics the soxhlet extraction process does not achieve complete recovery of the absorbed mixture of 1 4 C-labelled synthetic triglycerides. In this method the mixture of 1 4 C-labelled synthetic triglycerides that remains after soxhlet extraction is released by dissolution or combustion. The combustion method is suitable for all plastics, the dissolution method is only suitable for polymers that are soluble in a suitable solvent, e.g. tetrahydrofuran.
NOTE 2 Good sensitivity can only be achieved for samples of very low mass, e.g. for thin films. The specific radioactivity of the mixture of 1 4 C-labelled synthetic triglycerides routinely used is approximately 200 dpm/mg. In routine tests the limit of determination in liquid scintillation counting is in the order of 20 dpm per sample, for combustion, and 1 0 dpm per sample, for dissolution. In combustion only aliquots up to approximately 50 mg can be used. Consequently the determination limit for retained simulant is in the order of 0,1 mg to 50 mg.
It is apparent that for heavy test specimens the method gives only an estimation of the retained simulant. The dissolution method, which is generally preferred, results in similar figures. A higher specific radioactivity of the simulant would improve the determination limit. Migration into the mixture of 1 4 C-labelled synthetic triglycerides is calculated by subtracting the mass of 1 4 C-labelled synthetic triglycerides retained by the test specimen from the mass of the test specimen after removal from the 1 4 C-labelled synthetic triglycerides, and then subtracting this mass from the initial mass of the specimen. The total loss in mass is expressed in milligrams per square decimetre of surface area of the specimen and the overall migration is reported as the mean of a minimum of three determinations on separate test specimens. To allow for inaccuracies which may arise during the procedure and which may be difficult to detect, due for example to contamination or loss of the 1 4 C-labelled synthetic triglycerides during the sample handling stages, quadruplicate determinations are carried out on the sample allowing for the result from one specimen to be discarded. This method includes variations which are applicable to certain plastics and to experienced laboratories.
3.2 Reagents NOTE All reagents should be of recognized analytical quality, unless otherwise specified.
3.2.1 Mixture of 14 C-labelled synthetic triglycerides, simulant D as specified in 5.2 of EN 1 1 86-1 :2002. NOTE Details of suppliers can be obtained from CEN.
3.2.2 Extraction solvent (see 10.1 of EN 1186-1:2002). Pentane 98 % (mixed isomers) boiling point 36 °C. WARNING Pentane is a very volatile and highly flammable solvent. Take care when using and handling this solvent to prevent contact with sources of ignition. It is not recommended for extractions with this solvent to be left unattended, particularly overnight. NOTE Due to low boiling point of the solvent, cooled condenser water can be used to prevent undue loss of the solvent from the condenser. Other suitable solvent. NOTE In previous methods for determining overall migration into 1 4 C-labelled synthetic triglycerides the extraction solvent used has been 1 ,1 ,2 trichlorotrifluoroethane. For environmental reasons the use of this solvent should be avoided where possible, see 1 0.1 of EN 1 1 86-1:2002. Experience has shown that this solvent although effective for most plastics requires longer periods of extraction.