Scientific analysis is necessary when deciding upon the correct treatment method that should be used to conserve or restore artefacts including both old masterpieces and modern contemporary art works. The identification of the origin of materials in such artefacts is not straightforward. Modern paintings can be especially challenging because they incorporate synthetic organic pigments developed since the industrial revolution. These newer pigments are complex. Therefore, molecular information is key for identification, and surface analysis techniques could potentially be extremely valuable for studies of synthetic organic pigments and paints. Surface analysis may even assist in identifying the origin of such paints.

To this end, we will address the growing demand from scientific and technological research to specify the local composition of a sample in terms of molecules rather than elements. The ability of Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) to characterise pigments and paints is explored with valuable prior information about their chemical nature. This work demonstrates the potential of surface analysis techniques to contribute to a better understanding of modern paints for art conservators using a combination data-processing methods including Principal Component Analysis (PCA) and univariate analysis. In this work, pink and red paint flakes from a painting in Post-war art were validated against spectra from popular synthetic organic red quinacridone pigments [1]. The results obtained using ToF-SIMS and XPS in this study indicate that the flakes are of quinacridone origin rather than inorganic red pigments. This validation using our PCA model is likely to contribute effectively to the identification of the original materials in art works although further work will be needed to improve information on likely origin.

Reference: [1] Sano, N., Cumpson, P.J., Cwiertnia, E., Perry, J.J. and Singer, B.W., Surf. Interface Anal., 46, 786 (2014)

The ability to identify the source of atmospheric emissions is paramount to subsequently reducing particulate and aerosol pollution. Currently, source apportionment techniques utilize the quantitative profiles of a finite set of recalcitrant polycyclic aromatic hydrocarbons (PAHs) [1] followed by statistical attribution. These methods remain inherently limited by the exclusivity of the input values and the manner in which input values are handled [2]. Direct surface analysis of particulate matter (PM) by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) presents itself as an attractive alternative to targeted analysis by conventional solvent extraction and gas chromatography (GC) analysis due to direct surface analysis, minimal sample preparation and the ability to collect data on all species present.

In order to maximize the statistical power of the source apportionment technique employed, it is imperative to preserve the molecular ion of the PAHs, thus minimizing primary ion-induced fragmentation is critical. A systematic analysis of primary ions and their respective parameters is performed to determine the primary ion which yields the optimal signal from a certified reference material for source apportionment. Primary ions examined in this study include Bi⁺, Bi₃⁺, Bi₃⁺⁺, Cs⁺, C₆₀⁺ and C₆₀⁺⁺. The optimal primary ion is then utilized to examine the PAHs present on standard reference diesel particulates to examine the resultant statistical attribution following principal component analysis (PCA) and the impact on source apportionment techniques discussed.

[1] Liu, Y. et al. Atmospheric Environment, 107, 2015, 129-136.

[2] Belis, C.A., et al., Atmospheric Environment, 69, 2013, 94-108.

Explosives are mostly organic substances that rapidly release a large amount of energy during decomposition, which is dissipated as blast waves, propulsion of debris, or the emission of thermal and ionizing radiation. Millions of tons of explosives are used every year for obtaining minerals and metals from the ground; in most cases, explosive detonations are used for coal mining. Also, explosives have been used extensively in both military and terrorist context. The misuse of explosives, which jeopardizes public safety, requires that appropriate detection and analysis measures are in place. These should be able to characterize the explosives and identify their source. While secondary ion mass spectrometry (SIMS) is a well-established surface characterization technique, recent years have seen the emergence of a new technique employing MeV heavy ions beams to produce secondary ions from an insulating sample surface: “MeV-SIMS”. Unlike keV primary ions, MeV ions can be extracted through a thin Si₃N₄ window and travel a few millimetres in air enabling imaging with a submicron resolution under ambient conditions. This avoids negative vacuum effects on sample, simplifies sample preparation and significantly decreases the total analysis time. In addition to MeV-SIMS analysis which provides information on chemical composition of sample, PIXE analysis can be performed simultaneously and give information on trace elemental composition. The combination of MeV-SIMS and PIXE potentially gives a good quality image at high spatial resolution.

Samples of post blast material containing RDX, HMTD and PETN have been analyzed with ambient pressure MeV-SIMS using a 2MV Tandetron. Valuable information on the sample collection and storage has already been obtained. In this work we are aiming to identify the molecular signature of the explosive residues and their fragments in the spectra. For the spectra interpretation principal component analysis is performed to help specify and group different types of explosives. Additionally, results are also compared with keV-SIMS to demonstrate the sensitivity of the MeV technique.

[1] Erdmann N. et al., Spectrochim. Acta; B55; 2000; 1565-1575;

[2] Truyens J. et al., J. Environ. Radioact. ; 125 ; 2013 ; 50-55 ;

[3] Ranebo Y. et al., J. Anal. At. Spectrom. ; 24 ;2009 ;277-287.