Cutting-Edge Raman Spectroscopy Applied for Forensic and Heritage Studies

Raman spectroscopy, a powerful analytical technique, is increasingly being utilized in forensic science and cultural heritage preservation. Recent advancements have significantly improved its applicability in these fields, particularly with the development of portable instrumentation. This compilation, introduced by Maria Cristina Caggiani and Philippe Colomban from Sorbonne Université, CNRS, explores these innovations and their potential future applications (1). We have briefly looked at this article in a previous Spectroscopy News piece, but take a more detailed look now.

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Advanced Procedures in Raman Spectroscopy

In their introduction to the special issue titled "Advanced Raman procedures applied to natural/cultural heritage and forensic questions: Mobile set-up, data treatment, and associated techniques," Caggiani and Colomban delve into the latest methodologies in Raman spectroscopy. The focus is on multivariate statistical analysis of Raman spectra, the use of mobile instruments for in situ analysis, and the integration of Raman spectroscopy with other analytical techniques (1).

The use of mobile Raman spectrometers has become essential due to the challenges in transporting valuable artifacts to laboratories. This need for onsite, non-invasive analysis aligns closely with the constraints faced in forensic investigations, where evidence must be preserved and analyzed without alteration (1,2).

Artifacts arranged in a display case at an archaeological museum, showcasing the fruits of excavation. [Artifacts arranged in a museum display case] | Image Credit: © Julia - stock.adobe.com

Mobile Instrumentation and In Situ Analysis

Several studies featured in the special issue demonstrate the efficacy of mobile Raman spectroscopy. For example, Fornasini et al. analyzed Medieval soapstone artifacts using both laboratory and mobile Raman instruments, showing that mobile setups can provide quick and accurate preliminary identifications directly at archaeological sites (3). Similarly, Burlot et al. employed mobile Raman spectroscopy to study 18th-century enameled objects from France and China, identifying pigments and glass matrices with high precision (4).

In another notable study, Caggiani et al. used mobile Raman spectroscopy to examine semi-precious stones in Hellenistic-Roman glyptics. This non-invasive approach allowed for the analysis to be conducted on-site with minimal interference, highlighting the technique's practical benefits in cultural heritage preservation (5).

Integration with Other Techniques

Mobile Raman spectroscopy is often coupled with other portable analytical techniques, such as portable X-ray fluorescence spectroscopy (pXRF). This combination enhances the depth and accuracy of the analysis. For instance, Vieira et al. combined handheld Raman spectroscopy with micro-SORS to characterize Medieval paints, demonstrating the advantages of an integrated approach (6).

In forensic science, Almehmadi and Lednev compared bloodstain spectra obtained using a handheld Raman spectrometer with those acquired from a benchtop Raman microscope. The handheld device, equipped with a standoff attachment, provided visually similar spectra, supporting its potential for crime scene investigations (7).

Data Treatment and Multivariate Analysis

A significant challenge in using portable Raman devices is the often lower quality of the spectra they produce. To address this, the special issue emphasizes the importance of advanced data processing techniques. Multivariate statistical analysis, a subset of chemometrics, has proven to be highly effective in compensating for these limitations. This approach has been widely used in other fields, such as agriculture and medicine, and its application in Raman spectroscopy is gaining traction.

Future Perspectives

The special issue editors, Caggiani and Colomban, highlight several promising future directions for Raman spectroscopy. These include the increased use of multivariate analysis to handle large datasets from in situ analyses and the combination of different mobile analytical techniques for comprehensive studies. Additionally, the creation of databases from literature data and the development of open-access software for spectral data conversion are seen as crucial steps forward.

In conclusion, the advancements in Raman spectroscopy showcased in this special issue hold significant promise for both forensic science and cultural heritage preservation. The integration of mobile instrumentation, enhanced data treatment, and multivariate analysis is revolutionizing these fields, providing new opportunities for in-depth, non-invasive analysis directly at the site of interest. This compilation serves as a call to action for the Raman spectroscopy community to continue innovating and applying these advanced techniques in diverse contexts.

References

(1) Caggiani, M. C.; Colomban, P. Advanced procedures in Raman forensic, natural, and cultural heritage studies: Mobile set‐up, optics, and data treatment—State of the art and perspectives. J. Raman Spectrosc. 2024, 55 (2), 116–124. DOI: 10.1002/jrs.6633

(2) Chauhan, S.; Sharma, S. Applications of Raman spectroscopy in the analysis of biological evidence. Forensic Sci Med Pathol 2023 DOI :10.1007/s12024-023-00660-z

(3) Fornasini, L., Mantovani, L., Bertolini, M., Conversi, R. and Bersani, D., 2024. Multi‐analytical characterization of archaeological fragments of pietra ollare from the Medieval site ‘Piana di S. Martino’(Piacenza, Italy): A mobile and laboratory approach. J. Raman Spectrosc. 55 (2), pp. 232–245. https://doi.org/10.1002/jrs.6638

(4) Burlot, J.; Vangu, D.; Bellot-Gurlet, L.; Colomban, P. Raman identification of pigments and opacifiers: Interest and limitation of multivariate analysis by comparison with solid state spectroscopical approach—I. Lead-tin and Naples Yellow. J. Raman Spectrosc. 2024, 55 (2), 161–183. DOI: 10.1002/jrs.6600

(5) Caggiani, M. C.; Cavarra, M.; Barone, G.; Coccato, A.; Manenti, A. M.; Mazzoleni, P. Corroborating the autoptic identification of archeological glyptics in museum collections: The contribution of portable Raman spectroscopy. J. Raman Spectrosc. 2024, 55 (2), 200–215. DOI: 10.1002/jrs.6588

(6) Vieira, M.; Melo, M. J.; Conti, C.; Pozzi, F. A combined approach to the vibrational characterization of medieval paints on parchment: Handheld Raman spectroscopy and micro-SORS. J. Raman Spectrosc. 2024, 55 (2), 263–275. DOI: 10.1002/jrs.6632

(7) Lednev, I.; Almehmadi, L. A. Stand-off Raman spectroscopy is a promising approach for the detection and identification of bloodstains for forensic purposes J. Raman Spectrosc. 2024, 55 (2), 227–231. DOI: 10.1002/jrs.6609