Storage history
Temperature excursions, freezing or age can affect suspension condition.
Population metrics
Mean diameter does not describe the entire population
| Metric | Meaning | Why it matters |
|---|---|---|
| Mean / peak diameter | Central size result assigned to the lot | Reference point for calibration or selection |
| Standard deviation | Absolute spread around the mean | Shows population width in size units |
| Coefficient of variation (CV) | Standard deviation divided by mean, usually percent | Allows relative comparison across sizes |
| Distribution shape | Symmetry, tails or multiple populations | Can expose agglomerates or secondary populations |
| Uncertainty of certified mean | Doubt in the assigned mean result | Separate from the spread of individual particles |
Resolution
A narrow population can reveal instrument performance
A narrow standard can help evaluate size resolution and peak response. A broad or aggregated population can make an instrument appear less capable or shift the apparent peak.
Do not compare CV values without context. Measurement method, size range, lot, reporting convention and uncertainty all matter.
Agglomeration
A second population can be preparation-induced
Mixing
Under-mixing leaves settling; over-aggressive treatment may introduce bubbles or contamination.
Matrix chemistry
Ionic strength, pH or solvents can destabilize the colloid.
Container interactions
Adsorption and contamination alter the sampled population.
Certificate use
Tie the distribution to the exact lot
- Use the lot-specific mean and distribution values.
- Document the method used to characterize distribution.
- Set acceptance criteria that reflect the instrument objective.
- Investigate unexpected shoulders, tails or secondary peaks.
- Do not substitute nominal catalog values for certificate data.
Applied Physics technical pathway
Match the standard to the measurement—not the other way around.
Send the instrument, medium, target size, concentration, certificate and packaging requirements to Applied Physics for a technical recommendation.