Differentiation of paper types using element profiles generated using inductively coupled plasma-optical emission spectroscopy and inductively coupled plasma-mass spectrometry

The analysis of questioned documents in a forensic laboratory traditionally focuses on the visual examination of the physical properties of the paper such as brightness and thickness. Improvements in the paper making process have made visual differentiation of different types of paper difficult which has increased the research in the elemental analysis of paper. Inductively coupled plasma- mass spectrometry (ICP-MS) has been used to generate element profiles for paper samples; however, this technique is expensive and not widely available for forensic laboratories.;For this project, inductively coupled plasma-optical emission spectroscopy (ICP-OES) was investigated as alternative to ICP-MS analysis of paper sample. Four types of paper from the same manufacturer were microwave digested and analyzed by both ICP-OES and ICP-MS. Analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) test were used to determine if there were differences in element concentration within a paper type and among the four paper types. This had to be done separately for each element and each paper type so multivariate statistical procedures were used to compare the full element profile of all paper types simultaneously. Principal components analysis (PCA) and hierarchical cluster analysis (HCA) were used to assess the association among sheets of the same paper type and the differentiation among paper types.