Evaluation of portable Raman spectroscopy and handheld X-ray fluorescence analysis (hXRF) for the direct analysis of glyptics

A Micro-Analytical Study of the Scarabs of the Necropolis of Vinha das Caliças (Portugal)

Five scarabs and one scaraboid found in Vinha das Caliças 4 (Beja, Portugal) were analyzed using a micro-analytical methodology in order to determine their mineralogical and chemical composition. Microstructural characterization and chemical analysis revealed that all were composed of a white body of crushed feldspathic sand covered by a lead-rich, alkaline-depleted silicate blue-green glaze showing evident signs of glass deterioration. Variable pressure scanning electron microscopy with X-ray energy dispersive spectrometry, handheld X-ray fluorescence spectroscopy, and micro X-ray diffraction results show that blue-green color of the glaze was produced by using copper ions (Cu2+) in conjunction with the lead antimonate bindheimite, a yellow-colored opacifier. The introduction of small amounts of tin in the structure of bindheimite enabled the production of a ternary Pb-Sb-Sn oxide. Tin, which was most likely added with the copper source (bronze scrapings), is known to facilitate the crystallization of bindheimite. The results are consistent with the five scarabs and one scaraboid being manufactured in Egypt. This study, the first archeometric study of scarabs found in the Iberian peninsula, has greatly contributed to the understanding of the influence of the Eastern and Central Mediterranean world in the Southwestern Iberia during the first millennium B.C.

Feasibility of a handheld near infrared device for the qualitative analysis of bloodstains

One of the most common tasks in criminal investigation is to determine from which tissue source a biological fluid stain originates. As a result, there are many tests that are frequently used to determine if a stain is blood, semen or saliva by exploiting the properties of certain molecules present within the fluids themselves. These include chemical reagents such as the Kastle-Meyer or Acid Phosphatase tests, as well as other techniques like the use of alternative light sources. However, most of the tests currently available have some major drawbacks. In this study, a handheld near-infrared spectrometer is investigated for the specific identification of deposited bloodstains. First, a calibration was carried out by scanning over 500 positive (blood present) and negative (blood absent) samples to train several predictive models based on machine learning principles. These models were then tested on over 100 new positive and negative samples to evaluate their performance. All models tested were able to correctly classify deposited stains as blood in at least 81% of tested samples, with some models allowing for even higher classification accuracy at over 94%. This suggests that handheld near infrared devices could offer great opportunity for the rapid, low cost and non-destructive screening of body fluids at scenes of crime.

Development of a full micro-scale spatially offset Raman spectroscopy prototype as a portable analytical tool

We present, for the first time, a portable full micro-Spatially Offset Raman Spectroscopy (micro-SORS) prototype permitting the in situ analysis of thin, highly turbid stratified layers at depths not accessible to conventional Raman microscopy. The technique is suitable for the characterisation of painted layers in panels, canvases and mural paintings, painted statues and decorated objects in cultural heritage or stratified polymers, and biological, catalytic and forensics samples where invasive analysis is undesirable or impossible to perform. The new device is characterised conceptually in polymer and paint layer systems. The provision of portability with full micro-SORS delivers subsurface micro-SORS capability unlocking the non-invasive and non-destructive potential of micro-SORS at its most effective form permitting it to be applied to large and non-portable objects in situ without recourse to removing micro-fragments for laboratory analysis on benchtop Raman microscopes.