Analytical instrumentation in Life Sciences is one of the most rapidly evolving laboratory tool markets with approximately 5% growth rate in 20171. Microscopy methods offer useful information about the morphological and physical features of organic and inorganic materials.
Spectroscopic microanalysis methods and applications have usually trailed behind microscopic imaging because of the difficulties associated with low energy analysis; however, they are now gaining similar traction with new important discoveries in this field of science.
Environmental researchers have discovered that chemical contaminants in water impact marine wildlife in unforeseen ways. For instance, stain repellents used in carpets and nonstick coatings used in food packaging can drain into water bodies and are resistant to decomposition in the environment. These chemicals have been known to build up in the tissues of sea turtles, which feed on filter feeder mollusks such as mussels2. “These emerging chemical contaminants, or ECCs, are not necessarily all new substances. But with improved detection technologies, their unexpected potential impacts on the environment and human health are just now coming to light.”
Developments in Energy Dispersive Spectroscopy (EDS) detector technology play a vital role in the potential to investigate demanding applications in life sciences. Particularly, the Silicon Nitride window is almost 10 times thinner when compared to the older polymer window, which enhances the detection sensitivity for low-energy X-rays such as fluorine (F), oxygen (O), and nitrogen (N). These low-energy elements are major constituents of biological tissue, as well as toxic perfluorinated compounds (PFCs) in nonstick materials.
In a recent Scanning Electron Microscope (SEM)/EDS analysis of igneous rock — the key constituent of oceanic crust — it was shown that fluorine can be detected in trace concentrations in the range of 2% within nearly 10 seconds of spectral acquisition (Figure 1). Under similar conditions, it is possible to attain minimum detection limits of better than 0.5% F.
An analysis of the components of the marine-life shell also provide a valuable means of examining alternative “green” materials in construction infrastructure. Several countries rely on aquaculture as a major source of animal protein, but non-edible shells constitute 75% –90% of the food source, and therefore they are disposed of into the environment3. This can result in adverse consequences, for example, reduced oxygen levels in the water, or a foul odor in landfills. Therefore, it is essential to check the shells for unanticipated chemical compounds before putting these materials back into the environment as construction materials.
A SEM analysis of calcium carbonate in mussels from Brazil revealed that the CaCO3 from mussel and oyster shells is analogous in chemistry to commercial CaCO3, which makes crushed mussel shells a feasible option for construction material.
Figure 1. Igneous rock makes up most of the earth’s ocean crust, and naturally occurring fluorine is rapidly detected with an EDAX Octane Elect Silicon Drift Detector (SDD) with Silicon Nitride window.
Figure 2. An elemental X-ray map with variations in the main constituents, calcium in yellow and carbon in pink, indicating the differing areas of shell and tissue material. 150X magnification and 45 minute collection time with drift correction.
The SEM-EDS map represented in Figure 2 demonstrates that within a commercially available mussel from the US, there are differences in calcium (Ca) and carbon (C) intensities, with more oxygen and carbon in the darker parts of the shell. Spectral analysis (Figure 3) reveals that nitrogen is also present in these areas, which denotes that there might be leftovers of a thin layer of tissue membrane. Thanks to the advanced window technology, nitrogen detection in a thin membrane is now possible. The high resolution, visibly separating the low energy peaks, C, N, and O, obtained at 10 K CPS and 125 eV MnK resolution and 47 eV C resolution, is particularly remarkable.
Figure 3. The inside of a mussel shell at 500X magnification shows additional detail of the shell morphology and spectral analysis shows <50 eV resolution for C, N, and O. Trace level peaks of several minerals have concentrations lower than 1% by weight.
The analysis does not show any fluorine peak, which would denote PFC uptake at any level within the EDS detection limit. Quantitative analysis (Figure 4) reveals trace amounts of many minerals, and confirms the lack of fluorine.
Figure 4. The live-time quantitative analysis with APEX™ software, collected from the inside of a mussel shell with several trace minerals, but confirms there is no fluorine in the shell.
Developments in elemental detection for low energy X-ray microanalysis have revealed new applications of SEM-EDS in the Life Sciences. Thin Silicon Nitride window technology combined with high-performance resolution at all conditions means that it is possible to detect even trace amounts of materials in biological tissue. The EDAX Octane Elect Super SDD coupled with APEX™ software simplifies the collection of spectra, quantification, and maps for data collection within minutes for the best in productivity.
- Strategic Directions International. (2017, January). The 2017 Global Assessment Report: The Laboratory Analytical & Life Science Instrumentation Industry.
- Chemicals In Our Waters Are Affecting Humans and Aquatic Life In Unanticipated Ways. (2008, February 21). Retrieved from: https://www.sciencedaily.com/releases/2008/02/080216095740.htm.
- Characterization of calcium carbonate obtained from oyster and mussel shells and incorporation in polypropylene. (2012, February 14).
This information has been sourced, reviewed and adapted from materials provided by EDAX Inc.
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