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HomeInterlaboratory comparison on the determination of the Volume Specific Surface Area (VSSA) of manufactured manomaterials
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The European Commission’s Joint Research Centre (JRC) is leading the development of an OECD Test Guideline (TG) for the determination of the Volume Specific Surface Area (VSSA) of manufactured nanomaterials. For this purpose JRC is collaborating with a group of experts for the preparation, execution and evaluation of preparatory work, including a collaborative study. The final draft TG will be presented for discussion and eventual approval to the OECD Working Group of the National Coordinators of the Test Guidelines Programme. As agreed in the first meeting of the group of experts, the JRC organized and evaluated an interlaboratory comparison (ILC) on the determination of VSSA of nanomaterials by gas adsorption according to the Brunauer, Emmet and Teller (BET) method and gas pycnometry, with participation of seven laboratories. The objective of this ILC was to obtain information on the general applicability domain of these two techniques, and the transferability of the testing protocol. The final aim of the protocol is to calculate the VSSA, which is dependent on the Specific Surface Area (SSA) and skeletal density. This VSSA ILC is the first of its kind and started by developing a standard operating procedure (SOP) and associated reporting file; the SOP is based on the SOPs shared by some laboratories with the JRC and takes into account the existing international standards in this field (ISO 9277:2010 and ISO 12154:2014). The ILC was launched in May 2020 and concluded in November 2020 by presenting the evaluation of the results in a dedicated meeting of the group of experts. It was designed as semi-blind exercise with codes randomly attributed to samples and each of the seven participating laboratories. The seven selected test materials included inorganic (metal oxides – zinc oxide, and two types of titanium oxide) and carbon based materials (graphene and a multiwall carbon nanotube (MWCNT)) as well as one organic pigment. The selected materials also cover various shapes with one, two and three dimensions in the nanoscale (e.g. fibre, platelets and particles) and a range of size distributions and aggregation. The availability of information on the material’s homogeneity was also a selection criteria. Thus, the selected set of test materials included four materials (metal oxides) that are (certified) reference materials for Specific Surface Area, two materials (MWCNT and the organic pigment) that were used in past ILCs within the Horizon 2020 NanoDefine project (http://www.nanodefine.eu/), and one material (graphene) from the JRC Nanomaterials Repository, which was analysed and showed adequate homogeneity according to ISO 13528:2015. The selected test materials were subsampled in the JRC Nanomaterials Repository facility, with the exception of the materials from NanoDefine that were already available in vials of 0.25 grams. Seven laboratories, from France, Germany, Italy, Spain, UK, Korea and the JRC-Ispra took part in this study by analysing a number of test materials according to a defined ILC matrix designed to decrease the resources needed per single laboratory. Hence, one of the materials was analysed by all laboratories and the rest of materials analysed by a minimum of three laboratories each. The laboratories had a varying degree of experience with the techniques. Three independent replicates per type of material were analysed according to the distributed SOP. The temperature ramp programme for degassing conditions was derived from the JRC’s thermogravimetric analysis of the test materials, which also illustrates their stability in the relevant range of temperature.. The seven laboratories reported results for the three measurands considered, i.e. (mass) Specific Surface Area, density and VSSA. The instrumentation in the laboratories included both equipment built in-house and commercial equipment. Some of the laboratories did not report triplicate analysis for skeletal density measurements. Therefore, the (preliminary) analysis done by JRC is based on the calculation of VSSA by multiplying the three values of the SSA replicate by the mean density of the relevant test sample. These data have been statistically evaluated by robust statistics according to the principles laid down in ISO 5725-5. The parameters calculated were the robust average or consensus value, the uncertainty of the consensus value, the repeatability and reproducibility and their respective relative standard deviations. The method performance characteristics assessed were the within-laboratory precision, expressed as the relative standard deviation for repeatability (RSDr), and the between-laboratory precision, expressed as the relative standard deviation for reproducibility (RSDR). Overall results show good repeatability with RSDr values less than 2% for all materials except for the organic pigment with RSDr <5%. The variability between laboratories was higher, with overall RSDR values less than 20% for all materials and measurands, in particular RSDR values less than 10% were obtained for the analysis of four materials (graphene, MWCNT, zinc oxide and one type of titanium dioxide) while higher variability, with RSDR values in the 10% - 20% range, was obtained in the analysis of the organic pigment, the fumed silica and one type of titanium dioxide.
- Published:
- Personal author(s): Barrero, Josefa ; Senaldi, Chiara ; La Spina, Rita ; Riego Sintes, Juan
- Themes: Scientific and technical research
- Subject: comparative study , nanotechnology , processing industry , research body , research method , research report , technical standard , testing
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| ISSN 1831-9424 | ISBN 978-92-76-37685-9 | DOI 10.2760/41115 | Catalogue number KJ-NA-30702-EN-N |
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| ISSN 1018-5593 | ISBN 978-92-76-37684-2 | DOI 10.2760/08026 | Catalogue number KJ-NA-30702-EN-C |
- Released on EU publications website:
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