Summary
ERM-FD100 is a certified reference material developed by the Joint Research Centre (JRC) of the European Commission for validation of nanoparticle sizing methods. It consists of monodisperse colloidal silica particles with a certified size distribution.
This application note demonstrates SAXS determination of particle size distribution for FD100, validating DANNALAB's SAXS methodology against the certified values. DANNALAB actively participated in the development and validation of this reference material and has been validated by the EC JRC for SAXS characterization of nanoparticles.
Background & Regulatory Context
Nanoparticle Characterization Challenges
Pharmaceutical nanoparticles require accurate size determination for:
- Regulatory compliance: FDA/EMA guidance on nanoparticle characterization
- Batch release: Size specifications must be met
- Biodistribution: Size affects tissue penetration and clearance
- Safety: Size-dependent toxicity concerns
- Stability: Aggregation detection
Why Reference Materials Matter
DANNALAB's Role
DANNALAB participated in:
- Development of FD100 reference material
- Inter-laboratory comparison studies
- Validation by EC Joint Research Centre
- Establishment of certified size values
Methods & Experimental Design
Sample Information
Material: ERM-FD100 (colloidal silica)
Certified size: Mean diameter 19.8 ± 0.5 nm (by TEM)
Dispersion: Aqueous suspension
SAXS Measurement
Instrument Parameters
- X-ray sourceCu Kα
- InstrumentLaboratory SAXS at DANNALAB
- Q range0.05-4.3 nm⁻¹
- SamplesMultiple samples, 18 differential patterns total
- AnalysisEasySAXS v2.2 analytical package *
* DANNALAB & EMBL participated in the development by industrial partner [1]
Results
Size Determination — SAXS vs. Certified Values
SAXS Number-Weighted
Dn(D) = 18.1 ± 1.2 nm
Maximum of distribution
TEM Certified (Number-Weighted)
~18 nm modal diameter
EC JRC ERM-FD100
Agreement
Excellent match
SAXS closely matches TEM
Distribution Type
Gaussian (single-mode)
Well-defined population
Additional Distribution Parameters (From SAXS)
| Distribution Type | Maximum Diameter | Method |
|---|---|---|
| Intensity-weighted DI(D) | 21.0 ± 1.3 nm | From SAXS data |
| Volume-weighted Dv(D) | 19.6 ± 1.3 nm | Inverse Fourier transform |
| Number-weighted Dn(D) | 18.1 ± 1.2 nm | Reconstructed from SAXS |
| TEM (number-weighted) | ~18 nm | Direct observation (certified) |
Figure 1. A mono-modal particle population with a modal diameter of 18 nm estimated with number-weighted particle size distribution by TEM (ERM FD100).
Figure 2. Volume-weighted particle size distribution Dv(r) for aqueous dispersion of FD100 shows a well-defined single-mode distribution. Particle radius is shown as abscissa.
Figure 3. Theoretical simulated scattering curve based on Gaussian distribution (teal) shown versus the experimental differential scattering curve (black).
The value for number-weighted distribution (Dn(D) = 18.1 ± 1.2 nm) obtained from the SAXS data closely matches the data obtained by TEM (modal diameter 18 nm). The shape of particle size distribution was found to be close to the Gaussian function.
Currently this silica dispersion is certified as ERM FD100 (European Reference Material) and routinely used at DANNALAB and many other laboratories for quality control and method validation.
Conclusion
Several different methods of analysis were used to obtain parameters of number-, volume- and intensity-weighted distributions from the experimental SAXS data. The development and validation of efficient methods for particle/pore sizing together with evaluation of standard reference materials is one of the areas of activity at DANNALAB.
References:
[1] The EasySAXS software package — developed by PANalytical BV in cooperation with DANNALAB and EMBL
[2] Certification Report: Equivalent Spherical Diameters of Silica Nanoparticles in Water ERM-FD100 — IRMM JRC EU (DANNALAB = Lab 29, see pp. 62–63)