Elemental Analysis of Colorless Nylon Rope Fibers Using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

Rope fibers are important pieces of evidence when ropes have been used in the commission of a crime. Current techniques used to analyze rope fibers include comparing physical and optical characteristics using microscopy, color and dye analysis using microscopy or chromatography, instrumental analysis using infrared spectroscopy, and elemental analysis using scanning electron microscopy with energy dispersive x-ray emission (SEM--EDX). Inductively coupled plasma-mass spectrometry (ICP--MS) has the ability to deliver information about the elemental composition of a material.;The rope fibers used in this research were all sampled from ropes purchased from retail locations. Ropes were chosen for their similarity in physical appearance and when possible, different companies of manufacture and countries of manufacture were chosen (see full list in Appendix B). The ropes were identified as nylon or nylon blend by their packaging and appeared colorless. Five or six 0.1g samples (depending on which rope) were taken from eight separate ropes and after digestion in nitric acid were run ten times on an ICP--MS. Analysis of elemental concentrations in fibers showed significant differences in concentration of four to ten elements when the elemental concentrations of the rope fiber samples were compared to each other. It was also observed that the elemental concentrations for samples taken within the same rope, when compared, did not differ significantly for more than one or two elements. Elemental analysis using ICP--MS is an efficient and sensitive technique that, when applied to rope fibers, can provide valuable information, adding another discriminatory technique to the visual, optical, and chemical analyses that are currently employed in crime laboratories.