Characterization of plastic films from trace element analysis using inductively coupled plasma-mass spectrometry

Trace element concentrations in two types of polyethylene film (colourless cling film and coloured garbage bags) have been determined using inductivel y coupled plasma-mass spectrometry (ICP-MS). Samples were digested with nit ric acid-hydrogen peroxide in a microwave digester. The measured trace elem ent profiles were then used to distinguish between garbage bags of identica l colour, but different manufacturing origins. Black bags were discriminate d from differences in concentrations of four elements (Mg, Al, Fe and Ba), orange bags were distinguished using Mg, Cr, Mn, Fe and Pb concentrations. The orange bags, which contain a significant concentration of Lead pigment additive, were also discriminated on the basis of their lead isotope ratios . The ability to distinguish and match such plastic samples can be of value as forensic evidence. Polyethylene cling films could not be discriminated by these methods because of the low concentrations of trace elements presen t and their high variability within a single sample.