Esam M. A. Ali

Evaluation of portable Raman spectrometer with 1064 nm excitation for geological and forensic applications.

The development of miniaturized Raman instrumentation is in demand for applications relevant to forensic, pharmaceutical and art analyses, as well as geosciences, and planetary exploration. In this study we report on evaluation of a portable dispersive Raman spectrometer equipped with 1064 nm laser excitation. Selected samples from geological, geobiological and forensic areas of interest have been studied from which the advantages, disadvantages and the analytical potential of the instrument are assessed based on a comparison with bench instrumentation and other portable Raman spectrometers using 785 nm excitation. It is demonstrated that the instrument operating with 1064 nm excitation has potential for expanding the number and types of samples that can be measured by miniaturized Raman spectroscopy without interfering fluorescence background emission. It includes inorganic and organic minerals, biomolecules within living lichen and endolithic cyanobacteria as well as drugs of abuse and explosives.

In-situ detection of drugs-of-abuse on clothing using confocal Raman microscopy

This study describes the application of confocal Raman microscopy to the detection and identification of drugs-of-abuse in situ on undyed natural synthetic fibres, and coloured textile specimens. Raman spectra were obtained from drug particles trapped between the fibres of the specimens. Pure samples of cocaine hydrochloride and N-methyl-3,4-methylenedioxy-amphetamine HCl (MDMA-HCl) were used in this study. Raman spectra were collected from drug particles of an average size in the range 5-15 microm. Despite the presence of spectral bands arising from the natural and synthetic polymer and dyed textiles, the drugs could be identified by their characteristic Raman bands. If necessary, interfering bands could be successfully removed by spectral subtraction. Furthermore, Raman spectra were recorded from drug particles trapped between the fibres of highly fluorescent specimens. Interference from the fibres, including background fluorescence, was overcome by careful focusing of the confocal beam and the resulting spectra allow ready differentiation from interference from the fibres substrate bands. Spectra of several drugs-of-abuse on dyed and undyed clothing substrates were readily obtained within 3 min with little or no sample preparation and with no alteration of the evidential material.

Analytical Raman spectroscopy in a forensic art context: the non-destructive discrimination of genuine and fake lapis lazuli.

The differentiation between genuine and fake lapis lazuli specimens using Raman spectroscopy is assessed using laboratory and portable instrumentation operating at two longer wavelengths of excitation in the near-infrared, namely 1064 and 785 nm. In spite of the differences between the spectra excited here in the near infrared and those reported in the literature using visible excitation, it is clear that Raman spectroscopy at longer wavelengths can provide a means of differentiating between the fakes studied here and genuine lapis lazuli. The Raman spectra obtained from portable instrumentation can also achieve this result, which will be relevant for the verification of specimens which cannot be removed from collections and for the identification of genuine lapis lazuli inlays in, for example, complex jewellery and furniture. The non-destructive and non-contact character of the technique offers a special role for portable Raman spectroscopy in forensic art analysis.

Raman spectroscopy of archaeological and ancient resins: Problems with database construction for applications in conservation and historical provenancing

The adoption of Raman spectroscopy as a screening technique for the presence of organic resins on diverse substrates is now being advocated for the first pass non-destructive examination of potential sites for limited sampling using other analytical techniques. The characterisation of ancient resins in art work and specimens recovered from archaeological excavations is critically dependent upon the analytical capability of Raman spectroscopy using different wavelengths of excitation from the visible to the near infrared and the interpretation of the data illustrates the advantages and limitations of the technique. Resin specimens from art works and artefacts span a period of about 7000 years of recorded history and the influence of factors such as the environmental degradation, burial deposition, reaction with associated substrates and mineral pigments on the observed Raman spectra have been assessed. The key molecular Raman spectral features that are definitive for the discrimination between contemporary resins are considered in respect of these factors and thereby illustrative of the difficulties posed for the creation of a Raman spectral database of ancient resins, in contrast with the extensive and definitive literature equivalents that are available for their mineral pigment and organic dye analogues.

The detection of flunitrazepam in beverages using portable Raman spectroscopy

Portable Raman spectroscopy has been used for the detection of the date-rape drug flunitrazepam in spiked beverages that may be involved in cases of drug-facilitated sexual assault. Solutions of flunitrazepam with different concentrations were prepared in water and for each beverage type. Although some bands attributable to the beverage matrix are present, they did not interfere with the identification of the drug. Definitive evidence for contamination of the spiked drink concerned can be acquired within 10 s. The data can be acquired in situ and sample extraction and/or preparation steps are unnecessary. The ability of portable Raman spectrometers to interrogate spiked alcoholic beverages with flunitrazepam has been demonstrated. Copyright

The preservation of archaeological brain remains in a human skeleton

The identification of biomass within the cranial cavity of a waterlogged human skeleton inside a fish-tailed wooden coffin from a nineteenth century burial has been confirmed as brain tissue. A comparison is made between the Raman spectra obtained in the current study with those from an Iron Age brain found in an isolated cranium dating from about 500 years BCE, the only other Raman spectroscopy study made of human brain recovered from waterlogged, archaeological excavations. The spectra give some surprisingly detailed information about the state of preservation of brain tissue in both burials, especially when it is realized that, unlike preserved bog bodies, no other soft tissue has survived. The biosignatures of proteinaceous brain material are well characterized. The presence of spectral signatures from extraneous cyanobacterial colonization in the depositional site of the Iron Age brain had been construed to be responsible in part for the unusual preservation of brain tissues in the waterlogged environment, but they were not detected in the current study of the nineteenth century brain. The challenges for Raman spectroscopic analysis of biomaterials under these conditions are reviewed in the light of the successful outcome of the experiments. This article is part of the themed issue ‘Raman spectroscopy in art and archaeology’.