August 15, 2017 The National Physical Laboratory (NPL) is now recruiting participants to a VAMAS inter-laboratory comparison on number concentration of colloidal nanoparticles. Nanoparticles are increasingly used in innovative products manufactured by advanced industries and provide enhanced, unique properties of great commercial and societal value. The measurement of number concentration of particles in colloidal suspension is of major commercial interest as it enables the optimisation of materials specification and design, and is essential for risk assessment and quality control. It also supports compliance with regulation and underpins any claim to reliability, performance and lifetime in the formulation of products containing particles. In recent years there have been substantial advances in the ability to directly measure particle concentration in colloidal suspension. However, no formal evaluation and validation of available techniques have taken place and nanoparticle reference materials that are certified for number concentration do not yet exist. NPL is launching an interlaboratory comparison (ILC) under the umbrella of VAMAS (Versailles Project on Advanced Materials and Standards) as the basis for standardisation activity in the measurement of number concentration of colloidal nanoparticles. The ILC will request participants to measure the number concentration of 30 nm colloidal gold nanoparticles with at least one of four techniques: UV-Vis spectrometry, single-particle inductively coupled plasma mass spectroscopy (spICP-MS), particle tracking analysis (PTA) and differential centrifugal sedimentation (DCS). The samples will be provided by NPL along with a protocol, while the contribution of the laboratories to the study is in kind. Outcomes from the study will be disseminated through a peer-reviewed scientific publication and will contribute to future standards (ISO, CEN, etc.) in the area. NPL intends to distribute the materials for the study by the end of September 2017 and collect the results in January 2018. If you are interested in participating to the study (VAMAS TWA34, Project 10) with one of more of the listed techniques, please contact Caterina Minelli at NPL by 15 September 2017.