Coral CRM: CRMS Nano-Pellet – our next microanalytical certified reference material
Monday, March 28, 2022

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Corallium Rubrum Mediterranean Sardinia Nano-Pellet (CRMS-NP) after Apatite-NP is our second certified Nano-Pellet, which myStandards produced following the provisions of ISO 17034. Here you will learn why a coral was chosen as our next certified reference material and what its applications are.

Corals and their impact on the climate & climate research and beyond

Corals are sessile organisms living in colonies in a variety of waters. Their polyps excrete calcium carbonate (CaCO3) and incrementally build a solid skeleton. The reef-forming corals of today have been part of our ecosystem for approximately 240 million years. Coral reefs are home to a quarter of all marine life. While growing they bind a lot of the harmful CO2 gas. Therefore, corals, understandably, are protected and their trade is restricted. This protection however cannot save them from another threat, ocean acidification. Due to an increased concentration of CO2 in the atmosphere more CO2 is dissolved in the oceans creating carbonic acid (H2CO3), which in turn dissolves CaCO3, the corals’ skeleton. While CO2 acidifies the oceans it warms the planet and in turn the oceans, which causes corals to reject symbiotic microbes on which they rely for sustenance and ultimately starve. Further, fishing trawlers damage corals on the ocean floor. Historically, species of corals like this have been used as a gem as well.

During their growth corals record changes in temperature and other environmental factors, both natural and man-made. This information is saved in the skeleton in the form of chemical elements. Using microanalytical techniques like laser ablation (LA-ICP-MS) this information can be extracted. These analyses can also be used to fingerprint the corals’ origins and determine whether gems are genuine or not.

The coral we process is a red coral from the Mediterranean Sea off the coast of Sardinia. This is also the origin of the name we have given to the reference material: Corallium Rubrum Mediterranean Sardinia Nano-Pellet (CRMS-NP).

International legislation has restricted the trade of corals. In Germany, this law was ratified on September 19th 2000. The coral we processed was collected prior to this date and as such is exempt from trade restrictions. Nevertheless, we treated this material conscientiously to create a high-quality certified reference material.

Origin of the coral we process into certified reference material (CRMS-NP) - Mediterranean Sea, coast off Sardinia.
Origin of the coral we process into certified reference material (CRMS-NP) - Mediterranean Sea, coast off Sardinia.

Why a coral for the development of a certified reference material

Because corals are important for palaeoceanography, having a suitable reference material is vitally important. This assessment is confirmed by the fact, that our reference material JCp-1-NP is highly sought after and has sold out. Recreating it is currently not possible, which is why, at the beginning of 2021, decided to create our own coral certified reference material and add it to our portfolio.

The path from coral to Nano-Powder to Nano-Pellet

After having chosen the material which was to become the basis for our first certified Nano-Pellets, a production plan, following the provisions of ISO 17034 was made. The first step in this plan was thoroughly cleaning the starting material, i.e. 250 g of coral powder. Thereafter, the material’s identity was confirmed by X-ray diffraction. Our team processed 250 g of coral powder by means of wet-milling, freeze-drying and homogenisation in our production laboratory. Subsequently, the powder was divided using a rotary sample splitter yielding a total of 38 batches contained in glass vials. For storage the vials are vacuum-sealed with silica-gel and stored in an automated desiccator. Batch number CRMS-NP-2021-06-B01 was completely pressed into 44 Nano-Pellets, 7 of which were checked for homogeneity and stability using LA-ICP-MS. The chemical analyses were performed in two ISO 17025 accredited laboratories.

After systematic sample evaluation the data were condensed into the certificate of analysis. The certificate contains the certified values including their combined and expanded uncertainties resulting from characterisation as well as homogeneity and stability testing. All these steps were performed meticulously following ISO 17034 and, according to this standard, are mandatory when calling a material or rather its attributed values certified.

You can find an example of our data evaluation and the certification report with further information on the CRMS-NP product page.

By the way, we are always interested in Feedback: In case you would like to see additional elements, isotopic ratios or further information which are not in the certificate or certification report feel free to contact us! It is possible to press Nano-Pellets out of the remaining powders for other methods, e.g., LIBS or micro-XRF. These Nano-Pellets, because they lack a homogeneity- and stability test, will not be designated as certified, but are very well characterised for their chemical composition.

One of our CRMS Nano-Pellets with remnants of the processed coral.
One of our CRMS Nano-Pellets with remnants of the processed coral.

Corallium Rubrum Mediterranean Sardinia Nano-Pellet in practical application

As mentioned, using microanalytical techniques a lot of information can be extracted from corals. For example, the ratio of magnesium (Mg) to Calcium (Ca) in the coral skeleton is temperature dependant. This so-called proxy is called the Mg/Ca-ratio and can be measured using microanalytical techniques, thereby enabling researchers to reconstruct ocean temperatures in earth’s history and calculate climate models.

In part environmental contaminations can also be recorded by analysing heavy metals such as lead (Pb) in corals found near populated coastlines or river deltas, thereby allowing investigations of human pollution.

Another application is the chemical fingerprinting of the corals’ origin. This is critical to enforce trade restrictions. In all three potential applications laser ablation inductively coupled mass spectrometry (LA-ICP-MS) is a suitable analytical technique. To achieve accurate results using reference materials is essential. CRMS-NP is perfectly suited for this task, when analysing corals or other calcium carbonates.

Section of the periodic table showing the element with the highest concentration contained in CRMS-NP: Calcium (Ca).
Section of the periodic table showing the element with the highest concentration contained in CRMS-NP: Calcium (Ca).

Matching accessories and an outlook on microanalytical reference material sets

The CRMS-NP Nano-Pellets from this batch, similar to Apatite-NP, where all pressed in 10 mm diameter. Our self-developed bespoke mounts are perfectly suited for LA-ICP-MS. They come in two sizes and materials, geological thin-section or 1-inch round and either made from aircraft aluminium eloxed with diamond-like carbon (DLC) or 3D printed out of a polymer.

The thin section-sized mount holds up to 6, the 1-inch round up to 3 10 mm Nano-Pellets. Of course, not all places must be filled with CRMS-NP. Empty spaces can be filled up using other materials from our portfolio, or even just a dummy pellet so the hole does not disturb the gas flow in the ablation cell.

CRMS-NP is the second of our further microanalytical certified reference materials (CRM), which will be released during the course of the year. Further carbonates and iron ores will follow, as well as sets we have put together. These sets will be offered in a custom made and practical case. Stay tuned!

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