Characterization of Undigested Particulate Material Following Microwave Digestion of Recycled Document Papers

Abstract

Recycled document paper was microwave digested in a solution of HNO(3) and H(2)O(2) prior to analysis by inductively coupled plasma mass spectrometry (ICP-MS) to determine the trace elemental concentrations within the paper. Undigested particulate material was observed and subsequently characterized as a mixture of kaolin (clay) and TiO(2) by Fourier transform infrared spectroscopy and X-ray diffraction spectroscopy. The effect of the particulate material on the elemental concentrations was then investigated. Paper samples were completely digested in hydrofluoric acid (HF) and element concentrations determined in the HF and HNO(3)/H(2)O digests were statistically compared using Student's t-test (95% confidence limit). Statistical differences in element concentrations between the two digests were observed for only four elements and there was no evidence of element adsorption by the particulate material. Hence, the HNO(3)/H(2)O(2) digestion proved sufficient to digest paper for ICP-MS analysis, eliminating the need to use the hazardous and corrosive HF matrix.

Determination of Trace Elemental Concentrations in Document Papers for Forensic Comparison Using Inductively Coupled Plasma–Mass Spectrometry

“…The paper in the quartz vessel was partially digested; the resulting solution was clear with a small amount of white particulate matter. The particulate matter was chemically characterized and is discussed in more detail in the accompanying Technical Note (31). Through characterization and analysis of the particulate matter, it was determined that the concentrations of the elements of interest in the clear digest solution were not affected by the presence of the undigested particulates.…”

Forensic Science

“…The ASTM standards for the forensic examination of inks were reviewed; improvements were proposed, and the influence of storage conditions on the aging of color dye-based inkjet printing inks was reported . The analysis of paper within the field of document examination was reported using digestion followed by ICPMS, , and a comparison of XRF, LA-ICPMS, and IRMS methods . The sequence of intersecting gel pen and laser printed strokes was studied, as was the use of quantum dots for ink jet printing of security documents and labels, the characterization of toners using LA-ICP-TOF-MS, and the investigation of historical documents by energy dispersive X-ray fluorescence .…”

Atomic spectrometry update. Industrial analysis: metals, chemicals and advanced materials

“…In another, quite different application, LIBS has been employed as a means of identifying analgesic pills 132 by a comparison of the spectra over 200-1000 nm with reference spectra stored in a computer based spectral library. Historically, many techniques have been applied to the characterisation of paper [133][134][135] and one LIBS application has been used for the forensic identification of confidential documents, 136 by comparison of the spectra with reference spectra of a range of documents. Linear and rank correlation methods both yielded excellent identification probabilities of a range of documents.…”