Optimized Sample Preparation for Glass Fragments by Scanning Electron Microscopy–Energy Dispersive X-ray Spectrometry

ABSTRACT

Quantitative analysis by scanning electron microscopy–energy dispersive X-ray spectrometer (SEM–EDX) requires a flat and smooth sample surface. To fulfill these requirements, an embedding procedure is generally used for sample preparation. This approach is impractical for small glass fragments, which are frequently the subject of forensic examination. The authors report the use of optical microscopy for selecting glass fragments that are smooth and flat as possible and directly placing them on a scanning electron microscopy stub. The results using two SEM–EDXs were compared for embedded and nonembedded glass standards. No significant differences in accuracy, precision, reproducibility, and false answer rates were observed using likelihood ratio models suggesting that the reported method of sample preparation is suitable for forensic analysis.

KEYWORDS:

• Forensic science
• glass fragments
• scanning electron microscopy–energy dispersive X-ray spectrometer

Acknowledgments

The authors wish to thank Mr. Knut-Endre Sjastad, National Criminal Investigation Service, Oslo, Norway, for preparing embedded glass samples, and Mr. Colum McCarthy, Scottish Police Authority, Forensic Services, Glasgow, UK for helpful comments and language support.