SIMS2015 Session FE1-WeM: Forensics & Environment

Heartwood formation study is of great interest in the discovery of new natural compounds. It usually follows the death of parenchyma cells and tyloses formation. Cell apoptosis seems to be correlated with the biosynthesis of secondary metabolites, allowing trees to defend themselves against pests [1]. Although the analysis of secondary metabolites in ligneous species is now well established, their localization by surface analysis has not been fully explored [2]. Our purpose is to map the chemical composition in-between sapwood and heartwood to understand heartwood formation process.

A TOF-SIMS IV mass spectrometer (ION-TOF GmbH, Münster, Germany) equipped with a bismuth cluster ion source (Bi₃⁺, 25 keV) was used. Samples of sapwood, heartwood and transition zone from Dicorynia guianensis,a tree species from French Guiana, which is well-known for its decay-resistant heartwood, were imaged after being cut with a diamond knife. A first set of images has been recorded over large areas with 8 µm pixel size. Then, submicron resolution ion images have been acquired. To overcome the topographic effect and to obtain simultaneously high spatial and mass resolution, delayed extraction of secondary ions was characterized, and used [3].

Lignin and polysaccharides fragment ions have been mapped using the mass assignments from Goacher et al. [4]. A strong spatial correlation between lignin and polysaccharides ions has been established. Tryptamine fragment ions were also detected, with higher intensities detected in heartwood than in sapwood. This demonstrated that the biosynthesis of tryptamine mostly occurs in the heartwood formation process. High spatial resolution (0.4 µm) images acquired by tuning the mass spectrometer with a delayed extraction revealed that in the heartwood region tryptamine fragments are localized in parenchyma cells from transition zone and then diffuse to all heartwood cell walls. Heterogeneous distribution of tryptamine indicates this compound can be involved in the durability of heartwood. Decrease in inorganic and starch fragment ion intensities indicate that heartwood is less nutrient for pest insects.

These comparisons between different wood tissues bring new and extensive information to understanding heartwood formation.

This work has benefited from an “Investissement d’Avenir” grant managed by the Agence Nationale de la Recherche (CEBA, ref ANR-10-LABX-0025).

[1] Kampe, A. et al. Plant Cell Monographs 2013, 20: 71-95.

[2] Saito, K. et al. Anal. Chem. 2008, 80: 1552-1557.

[3] Vanbellingen, Q. P., Elie, N. et al. Rapid Commun. Mass Spectrom. In press DOI:10.1002/rcm.7210.

[4] Goacher, R. E. et al. Anal. Chem. 2011, 83: 804-812.

Secondary ion mass spectrometry (SIMS) is a useful microanalytical method to exploit isotopic signatures resident in enrichment facilities and assists in determining an estimate of the enrichment levels and operational history via particle analysis. SIMS is particularly well equipped to detect and analyze actinide elements in swipe samples from declared facilities to verify if reactor operations are consistent with safeguards declarations or expectations. Additionally, SIMS can quickly and accurately identify particles of unique isotopic composition in the presence of a large number of “dirt particles” with nominally natural isotopic composition.

Recently, SIMS has become a powerful tool for the direct assay of the isotopic distributions of nuclear and non-nuclear particles from conductive swipe materials. New surface sampling materials that enable this direct SIMS analysis have the potential to eliminate traditional sample preparation methods that are excessively time consuming and cost prohibitive. Initial experiments were performed with an activated carbon material used to swipe a vial containing a NIST traceable standard (CRM U850) with a ²³⁵U enrichment of 85%. Direct analysis by SIMS on a representative subset of regions-of-interest identified 12 unique particles with an average ²³⁵U/²³⁸U ratio of 6.228 ± 0.136 (NIST certified value is 6.148 ± 0.006). These preliminary results demonstrate the viability of conductive carbon swipe materials for direct SIMS assay of surface samples for uranium particle isotopic analysis with relevance to nuclear non-proliferation safeguard samples.

Additionally, a novel particle analysis algorithm known as SEEKER has been developed at PNNL to improve the identification of unique particles from SIMS image analyses. This algorithm combines adaptive thresholding and marker-controlled watershed segmentation (MCWS) to improve the SIMS isotopic analysis of uranium containing particles for nuclear safeguards applications. Particles of NIST traceable standards U129A, U150 and U500 were successfully identified in regions of SIMS image data where there was high variability in image intensity, particles were touching or were in close proximity to one another and/or the total amount of ion signal for a given region was count limited. Traditional algorithms fail to identify unique particles under these conditions and often lead to cross-contamination of isotopic data. The combined application of novel swipe materials for direct SIMS analysis with the SEEKER algorithm for processing SIMS image data represent a marked advancement in the application of SIMS to non-proliferation and nuclear forensics applications.

Several years ago we began a pilot study at the National Institute of Standards and Technology (NIST) to explore the potential use of cluster SIMS for spatially resolved analysis of contraband materials (explosives and narcotics). These experiments led to the growth of a new research program focused on the development and optimization of surface trace chemical analysis techniques for characterization of contraband materials to support civil aviation and military checkpoint security screening applications as well as forensics. This metrology and standards program has evolved to include the use of cluster SIMS on both magnetic sector and TOF SIMS instruments as well as various ambient ionization mass spectrometry approaches. In addition, we make use of various complementary techniques including optical, Raman and cathodoluminescence microscopies and ion mobility spectrometry. Technique development and optimization, especially for ambient MS techniques, is supported by a range of novel flow visualization and high speed video microscopy techniques. This presentation will provide a look “inside” the science of trace contraband detection technologies with an emphasis on measurement tools, standards and protocols we have developed in our laboratory. Included in the presentation will be a discussion of the critical role of standards in homeland security, the application of SIMS and related techniques to address problems in forensics and homeland security including trace drug analysis, chemical imaging of fingerprints, narcotics, explosives, fibers, paints and gunshot residue. Finally, we will provide a description of the use and characterization of test articles produced using 3D printing techniques and advanced materials deposition inkjet printer systems. These test articles include simulated fingerprints and chemical standards containing explosives, narcotics, drugs and gunshot residues.

The risks, toxicological effects to health and environmental impacts that arise from the manufacture, usage and disposal of flame retardants as additives in polymeric materials exceed their benefits in reducing the tendency of consumer products from igniting and burning. Major exposure routes of humans to flame retardants include inhalation, ingestion and dermal absorption. Based on the concerns associated with the high specific surface areas of flame-retarded polymers that make contact with skin, with resultant contact dermatitis, this study focuses on flame retardant diffusion through model systems.

Diffusion of brominated flame retardant additives on model systems of polymeric materials- Poly(methylmethacrylate) and Nylon 6, 6 has been studied using TOF-SIMS V. Two model systems consisted of a) PBDEs deposited on surfaces of thin films of PMMA spin cast onto silicon wafers and b) PBDE soaked Nylon prepared from interfacial emulsion polymerization. Sample thickness, determined by AFM profilometry, was used to correlate the time-scale of depth profiling in TOF-SIMS. ATR-FTIR spectra allowed for identification of polymeric materials. Static SIMS was employed to study bromine composition of the additives: BDE 183, BDE 47, BDE 209 and BDE 153 at different concentrations. For static SIMS, Bi₃⁺⁺ was found to be the optimum primary ion source that produced good spectra characteristics (for example, mass accuracy of additive peaks, intense secondary ion count, excellent bromine fragmentation pattern, and good signal-to-noise ratio). Cs⁺ monoatomic primary ion was used to depth profile model systems at differing temperatures. Low temperature profiles were found to produce improved normalized intensities. A constant profile of the major fragments of additives, observed through the models, indicate diffusion of PBDEs through polymeric materials from the surface.

Understanding processes governing energy and nutrient flow within phototrophic communities and the effects of perturbations upon these fluxes is vital to predicting how changing environmental conditions will affect carbon and nitrogen cycling in these communities. Because phototroph-heterotroph interactions are ubiquitous in nature, changes in C and N cycling within these microbial communities will exert global impacts upon the biogeochemical cycling, in turn influencing the climate. The metabolic activity of these communities is typically determined by bulk analysis of pure cultures, and the metabolic capacities of individual species are inferred by genomic data. Within the past decade, SIMS has emerged as a powerful technique that can directly visualize the metabolic activities of single cells within microbial communities. Here, we will discuss the role the NanoSIMS plays in our endeavors to elucidate linkages between predicted and expressed functions in phototrophic microbial communities. Initial work is being performed in unicyanobacterial consortia derived from the microbial mat that occupies hypersaline Hot Lake, USA, among others. Early work established a global view of the communities’ structure and function, including: (i) the relative abundance of species within the consortia, (ii) the proteins and metabolites present, and (iii) bulk stable isotope incorporation and growth rates under varying nitrogen source (i.e., nitrate, ammonium) conditions as consortial biofilms assembled. However, the NanoSIMS allowed us to gain unparalleled information of the actual flow of C and N through consortia. In providing relative quantitation of the consumption of these nutrients between autotrophs and heterotrophs, the NanoSIMS surprisingly uncovered linkages between a consortium’s nitrogen source and the rate of transfer of carbon, provided as bicarbonate, the community’s sole source of organic C, between the cyanobacterium and its heterotrophic consorts. These patterns strongly suggest that C substrates consumed by heterotrophs may be determined by the N source(s) available to primary producers, which in turn governs the relative abundance of species and their spatial distribution. Future work will include using spatially-resolved analytical approaches (i.e., species-specific antibody labeling) to directly identify species within these communities to relate this information back to nutrient flow, and employing complementary mass spectrometry imaging methods (e.g., ToF-SIMS, C₆₀ FTICR-SIMS, and MALDI) to provide molecular-specific information about the creation and flux of larger biomolecules within pure cultures and in complex communities.

Silver nanoparticles (AgNPs) are incorporated into a growing number of products that range from textiles to pesticides [1]. As their applications become more diverse, there is an increased risk of entry into the environment such as from groundwater runoff. Their unique properties raise concerns regarding their fate and transport and subsequent effects on plants and animals. While the presence of AgNPs in water, soil and plants has been established, the mechanism by which these are taken up into plants has not been determined [2]. The present work aims to study the uptake mechanism of AgNPs in Arabidopsis thaliana, a model plant. The imaging technique of Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) has been used to gain spatial distribution and spectral information characteristic of the plant, ionic Ag, AgNPs, and plants exposed to either ionic Ag or AgNPs. By varying the size or coating of AgNPs, effects on the mechanism and the location of the AgNP in the plant become apparent.

An ION-TOF V equipped with a bismuth primary ion source and a cryogenic chamber was used to study Arabidopsis in its native state. Cryo-ToF-SIMS images and spectra were collected from surfaces of frozen-hydrated Arabidopsis stem cross-sections treated with AgNPs or silver nitrate. Morphological features similar to those seen by optical microscopy were identified using the burst alignment mode of analysis (Figure S1A). Additional analysis on the same sample area using the high current bunched mode allowed for identification of specific regions where the AgNPs are present (Figure S1B). By using the ratio of Ag⁺/Ag₃⁺ (Figure S2), it is possible to distinguish the differences between ionic Ag and AgNPs within Arabidopsis in its native state while preserving spatial resolution.

[1] Rubiales, D. and A. Perez-de-Luque, Pest Manag. Sci. 2009, 65, 540-545.

[2] Wang, J. et. al. Environ. Sci. Technol. 2013, 47, 5442-5449.

Evaluation of harmful influence of particulate matter (PM) air pollution to human health requires a progress in monitoring techniques. Standard measurement equipment is usually large and expensive. In addition to such traditional, stationary instruments needed are personal and mobile devices to enable study of personal exposure.

Here we apply and develop a technique, which recently was presented by our group [1]. Namely, we treat wasted mobile phones as a personal collector of PM. We have been collecting wasted mobile phones, dismantling its’ housings and extracting the dust accumulated inside. We show results of PM extracted from over 200 pieces of mobile phones (of different models, and brands) received from inhabitants of two Polish cities: Krakow and Gdansk .

The collected samples are examined by three mass spectrometric techniques. In secondary ion mass spectrometry (SIMS) analysis we use rastered Ar⁺, 5keV ion beam for samples placed on a substrate of high purity indium. Depth profile analyses are performed with oxygen-flooding at 5•10^-7hPa. Bulk analysis of the collected samples is done using spark-source mass spectrometry (SSMS) and inductively coupled plasma mass spectrometry (ICP-MS).

Obtained results are compared with the results of PM collected with use of standard urban environmental monitoring systems of the two cities of Kraków and Gdańsk. Correlation between the corresponding results is presented.

Acknowledgements:

Authors thank The National Centre for Research and Development, Poland, for project no PBS1/A9/9/2012 founded in years 2012 – 2015.

References:

[1] P. Konarski, M. Miśnik, A. Zawada, K. Olszewska-Czopik, I. Iwanejko, M. Ścibor, B. Balcerzak, and J. Hałuszka; Surface and Interface Analysis, vol. 46, no. S1, pp. 389–392, 2014.

in-bottom:.0001pt;line-height:17.05pt;background:white'>