Characterization of document paper using elemental compositions determinedby inductively coupled plasma mass spectrometry

Comparison of the origin of successive pages of a multiple page document ca n provide important forensic evidence in cases of document fraud. The use o f elemental compositions, determined by inductively coupled plasma mass spe ctrometry (ICP-MS), to characterize paper is reported. Samples of commonly used office document paper (white, A4, 80 gsm) from seventeen different sou rces, were analysed for their elemental composition, after microwave digest ion in nitric acid-hydrogen peroxide solution. The limits of detection, ins trumental precision and potential matrix interferences were established for the 23 most abundant elements found in paper. The variability of distribut ion for these elements within a ream of paper was determined. Nine elements (Na, Mg, Al, Mn, Sr, Y, Ba, La and Ce) were selected as suitable discrimin ators because their concentrations were sufficiently high and uniform. All seventeen papers could be distinguished by statistical t-tests (99% confide nce) using only two of these elemental concentrations (Mn and Sr). The resu lts are also presented using ternary plots which use three inter-element as sociations to display the differences in paper composition. Four separate b atches of a single product line from the same mill, manufactured at monthly intervals, were also discriminated using elemental concentrations. Three u nknown samples, chosen randomly from among the seventeen papers, were corre ctly identified from their elemental composition; two unknown samples from the four batches were similarly identified. The results show that elemental analysis, using ICP-MS, provides an effective and robust technique for the discrimination of document paper.