2.4. Determination of the titanium content of the LDPE
films by acid digestion
To determine the content of titanium the LDPE films A, B and C
and the LDPE blank were digested. Each sample film was cut
into small pieces of about 3 mm 3 mm. Approx. 50 mg of
these pieces were weighed into polytetrafluoroethylene (PTFE)
cells. The cells were filled with 10 ml of 69% nitric acid (J. T.
Baker, for trace metal analysis) and stored in pressure vessels
for 13 h at 160 8C in a temperature controlled oven. At the end
of storage 0.5 ml of each sample was diluted with 9.5 ml ultrapure
water and analyzed for titanium by ICP-MS. For the
determination three identical samples of each material were
prepared.