Reference materials of defined particle size certified recently by the community bureau of reference of the european economic community

Some results from an international projects, supported by the Community Bureau of Reference of the European Economic Community, on the certification of five reference materials of defined particle size covering the overall range 0.35 – 650 μm are presented and discussed. Four of the reference materials were certified with respect to the mass distributions of the Stokes' diameters measured by an agreed gravitational sedimentation (Andreasen pipette) method. The coarsest of the reference materials was certified with respect to the mass distribution of the volume diameters of the particles using sieves, the ‘cut sizes’ of which were calibrated with respect to their equivalent volume diameters.Data were also obtained using several other methods, including X-ray gravitational sedimentation, sedimentation balance, centrifugal sedimentation, electrical sensing zone and photo-sedimentation methods. These were not used for certification but are presented for comparison purposes and to indicate the usefulness of the certified reference materials for the checking and calibration of many particle sizing techniques.