Table 1.
Relevant features of the measurement processes underlying the measurands used for the characterisation of ERM-FD102, and associated assigned particle diameter values
| Technique (-detection type) | Physical principle | Sample preparation and fractionation prior to detection | Type of particle detection | Data analysis | Type of diameter | Type of weighting | Averaging type | Assigned equivalent diameter (nm) ± expanded uncertainty (if applicable) (size range (nm) used in statistical analysis) | |
|---|---|---|---|---|---|---|---|---|---|
| Size class A | Size class B | ||||||||
| AF4-LS | Rate of diffusion by Brownian motion against a cross-flow | Diluted suspension, fractionated due to parabolic profile of laminar flow | Intensity of light scattered by ensemble of particles co-eluting at a given time point | AF4 theory | Sphere-equivalent hydrodynamic diameter | Scattered light intensity | Arithmetic meana | 22.9 (10–40) | 87.5 (60–120) |
| AF4-RI | Rate of diffusion by Brownian motion against a cross-flow | Diluted suspension, fractionated due to parabolic profile of laminar flow | RI increment by ensemble of particles co-eluting at a given time point | AF4 theory | Sphere-equivalent hydrodynamic diameter | Mass/volume | Arithmetic meana | 20.4 (10–40) | ND |
| AFM (amplitude modulation intermittent contact) | Imaging of surface topography by scanning the surface with an oscillating cantilever | Diluted, dried on substrate | Identification of individual, discrete particles in AFM image | Measurement of height (with elimination of touching particles) with respect to flat surface following height scale calibration | Sphere-equivalent diameter | Number | Modea | 16.9 ± 1.8 (5–40) | 80 ± 6 (30–90) |
| CLS-turbidity (line-start and homogeneous incremental) | Sedimentation rate | As-received suspension, fractionated through centrifugal force | Turbidity of ensemble of particles with the same sedimentation rate | Conversion of time to particle size through sedimentation time calibration (line-start incremental method) or conversion of sedimentation coefficients to particle size through Stokes’ law (homogeneous incremental method) | Sphere-equivalent Stokes diameter | Light extinction capacity | Modec | 23.9 ± 2.0 (10–40) | 88 ± 7 (60–150) |
| CLS-RI (homogeneous incremental) | Sedimentation rate | As-received suspension, fractionated through centrifugal force | RI increment by ensembles of particles with the same sedimentation rate | Conversion of sedimentation coefficients to particle size through Stokes’ law | Sphere-equivalent Stokes diameter | Volume/mass | Modeb | 18.0 ± 2.7 (5–35) | 88 ± 7 (75–105) |
| DLS | Rate of diffusion due to Brownian motion | As-received suspension | Fluctuations of the intensity of light scattered by the ensemble of all particles in the measurement volume | Numerical deconvolution of autocorrelation function | Sphere-equivalent hydrodynamic diameter | Scattered light intensity | Arithmetic meanc | 17.8 ± 1.5 (5–30) | 88.5 ± 2.2 (30–200) |
| Harmonic meanb | 17 ± 4 (5–30) | 84.8 ± 2.2 (30–200) | |||||||
| Modeb | 17.1 ± 2.4 (5–30) | 84 ± 9 (30–200) | |||||||
| Geometric meana | 16.8 (5–30) | 85.2 (30–200) | |||||||
| Mediana | 18.0 (5–30) | 85.9 (30–200) | |||||||
| EM | Electron beam imaging based on transmitted (TEM) or secondary electrons (SEM) | Diluted, dried on substrate | Identification of individual, discrete particles in EM image | Image analysis of 2D projections of particles measured (with elimination of touching particles) in relation to length scale calibration | Area-equivalent circular diameter | Number | Modec | 18.2 ± 1.6 (10–40) | 84.0 ± 2.1 (60–120) |
| Medianc | 18.3 ± 1.7 (10–40) | 83.3 ± 2.3 (60–120) | |||||||
| PTA | Rate of diffusion due to Brownian motion | Diluted suspension | Identification of individual particle trajectories in video image | Video analysis of tracked particles’ mean-square displacements and velocity in 2D through length scale and time calibration | Sphere-equivalent hydrodynamic diameter | Number | Modeb | ND | 78 ± 5 (10–150) |
| Arithmetic meanb | ND | 82 ± 4 (10–150) | |||||||
| Medianb | ND | 79.2 ± 2.2 (10–150) | |||||||
| SAXS | Angular distribution of X-rays scattered at surface of suspended particles | As-received suspension | Fluctuations of the intensity of X-rays scattered by the ensemble of all particles in the measurement volume | Guinier fit of high q-range of angular scattering pattern | Sphere-equivalent hydrodynamic diameter | Volume-squared | Arithmetic meana | 22.6 (NA) | ND |
| Numerical deconvolution of angular scattering pattern | Volume | Arithmetic meanc | 19.8 | 80.1 | |||||
| Scattered X-ray intensity | Arithmetic meana | 21.4 | 81.0 | ||||||
NA not applicable
ND not detectable
aAdditional material information
bIndicative value
cCertified value