U.S. flag

An official website of the United States government, Department of Justice.

NCJRS Virtual Library

The Virtual Library houses over 235,000 criminal justice resources, including all known OJP works.
Click here to search the NCJRS Virtual Library

Assessment of the Utility of X-ray Fluorescence for the Chemical Characterization and Comparison of Black Electrical Tape Backings

NCJ Number
Forensic Chemistry Volume: 13 Dated: May 2019
Meghan Prusinowski; Andria Mehltretier; Claudia Martinez-Lopez; Jose Almirall; Tatiana Trejos
Date Published
May 2019
6 pages
This study used X-ray Fluorescence (XRF) in the chemical characterization and comparison of black electrical tape backings and compared the utility of this process to previously published SEM-EDS and LA-ICP-MS data.

Elemental analysis of electrical tapes is typically conducted by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), although Laser Ablation-Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS) was recently shown to improve the sensitivity of the determinations. In the current study, three XRF systems were used to evaluate a range of configurations commonly available at crime laboratories. A set of 40 electrical tape backings known to originate from different sources were used to assess the inter-roll variability, discrimination, and classification capabilities of the method. The discrimination for this tape set increased from 78.8 percent achieved by SEM-EDS to 81.5-91.0 percent by XRF, depending on the instrumental configuration. In comparison, LA-ICP-MS achieved 84.6 percent discrimination on these tapes. The overall characterization, classification, and discrimination capabilities for this set improved as follows: SEM-EDS<iXRF<small spot size benchtop XRF with SDD, LA-ICP-MS<large spot size XRF. A set of 20 pieces of tapes collected from the same roll were analyzed for intra-roll variability. Duplicate control same-source samples were used to evaluate inter-day and intra-day instrument variability. No false exclusions were observed in the data set, demonstrating the within-sample variability and instrumental variability are relatively lower than the inter-sample variability. One concern of the method is the penetration depth of the X-ray beam beyond the target backing, requiring careful sample preparation to avoid interference from the adhesive or sample holder. XRF is a viable analytical tool for the forensic examination of electrical tapes, with advantages of speed of analysis, minimal destruction of the tape, and high informing power. (publisher abstract modified)