Apatite Nano-Pellets – our first microanalytical certified reference materialThursday, February 10, 2022
Since founding the myStandards GmbH in 2018 we have been driven by our vision of making certified microanalytical reference materials. The problem is known, the application of microanalytical methods has been hampered by a lack of suitable certified reference materials. Precisely because of this vacancy it is difficult to perform so-called traceable analyses. Traceable analyses are a prerequisite when manufacturing reference materials. How to make certified reference materials for these methods? A classic case of the chicken and egg problem. Since 2018 we have been trying to interpret and apply ISO 17034 in such a way as to enable the certification of microanalytical reference materials. It´s been a long time, since we began trying in 2018 and we´re finally there!
Properties and Applications of Apatite in its primal state
Apatite (chemical formula = Ca5(PO4)3 (OH,F,Cl)) is one of the most common phosphorous minerals on earth. It is brittle, the reference mineral on the Mohs-scale for a hardness of 5 and has a density of 3.2 g/cm³. Further, it is an important constituent of phosphorous ores used in the production of phosphate fertilisers and acids. Due to its optical properties, it is also sometimes used as a gem stone.
Naturally, apatite also has scientific applications. It is used as tool for petrogenetic, provenance and radiometric dating studies. Among other places the mineral can be found in Brazil, China, Canada, USA and Russia. Our material comes from the Arusha-Loliondo district in Tanzania, Africa.
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The road toward the first certified reference material in our portfolio
On our mission to revolutionise the geochemical solid-state analysis using our Nano-Pellets, the accreditation following ISO 17034 is an important milestone. Since we, to the best of our knowledge, are the first and only one with this goal using pressed powder pellets, each step is virgin soil and requires careful planning. An integral part of the accreditation process is the pilot-project, which as a certified reference material should be extremely useful to the applying community.
We chose apatite due to its dual applicability in both science and industry. Market research within laser ablation, an analytical technique to which our Nano-Pellets are very well suited, using “Apatite” and “LA-ICP-MS” as keywords on Google Scholar showed the number of results increasing by nearly 70 % between 2015-2020. From 2000-2015 there were 7500 results, today there are 11.000, which shows the increased interest in the analysis of apatite by LA-ICP-MS. In summary, the number of hits increased by 3500 within the last five years, which equates to 700 hits a year and roughly 2 per day.
From apatite crystals to Nano-Powder and 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. 5 kg of apatite crystals. Thereafter, a few fragments were crushed to ensure the material’s identity by X-ray diffraction. In total, our team processed 1.5 kg of crystals 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 86 batches contained in glass vials. For storage the vials are vacuum-sealed with silica-gel and stored in an automated desiccator. Batch number Apatite-NP-2020-07-B01 was completely pressed into 117 Nano-Pellets, 12 of which were checked for homogeneity and stability using LA-ICP-MS. The chemical analyses were performed in three 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 uncertainty 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 Apatite-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.
Apatite-Nano-Pellets and their practical application
The apatite Nano-Pellets have many certified values of important elements. Among them are the rare earth elements (REE) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) and Uranium (U) as well as Lead (Pb). REE are critical high-tech elements used in electronic industries and as such are indispensable in our modern world. When mining an apatite-rich REE ore it is crucial to know whether mining is profitable. Using our Apatite Nano-Pellet analytical instruments can accurately quantify the REE in the apatite-samples. Scientifically, REE give insights into magma formation and fluid-rock interactions, in summary rock-forming processes. U and Pb isotopes can be used for dating (Uranium–lead dating) terrestrial rocks as well as meteorites. The method uses the radioactive decay-chains of uranium isotopes. Correctly calibrated instruments yield the most accurate data, an application for our Apatite Nano-Pellets.
Apatite-NP and bespoke accessories
All Apatite Nano-Pellets from Batch Nr. 1 have a diameter of 10 mm. To make them easier to handle and use in laser ablation we have developed two mounts. One is modelled on a standard geological thin section capable of holding up to six Nano-Pellets, the other is a 1-inch round mount, capable of holding up to three Nano-Pellets. They are available in two materials, either 3D-printed out of a polymer or CNC-machined out of aircraft grade aluminium eloxed in diamond-like-carbon (DLC)©. Of course, you do not need to fill all available spaces with Apatite Nano-Pellets, feel free to choose any other material form our portfolio. In case you do not wish to have further Nano-Pellets we are happy to insert dummy-pellets, which prevent a disturbed airflow inside the ablation chamber.
Further information regarding our Nano-Pellets as well as our portfolio can be found in our downloadable flyer: