Elemental hair analysis using nuclear microscopy and X-ray energy dispersive spectroscopy

Abstract

Analysis of hair is a potential means of determining the body's trace elemental status, since throughout its growth hair may concentrate minerals and thus provide a record of the elemental status of an individual. However, levels of most trace elements in hair vary widely, often attributed to its surface contamination. Using both electron microscopy with X-ray energy dispersive spectroscopy and nuclear microscopy with proton-induced X-ray emission spectroscopy, we investigated the efficacy of five washing procedures on contemporary and historical hair samples. We conclude that persisting extraneous matter on hair is a likely source of inconsistency with bulk analysis even of washed hair samples. We therefore developed a technique, using the Oxford nuclear microscope, first to differentiate trace elements within hair from surface contamination and, secondly, to analyse accurately, at concentrations of parts-per-million, the elemental content in cross-sections of hair. All hairs in cross-section were shown for the first time to have three distinct types of distribution of elements across the hair shaft.