How to Read a Certificate of Analysis (COA) for Nanopowders

A Certificate of Analysis (COA) is the manufacturer’s record of what was measured on a specific batch. For nanomaterials it is one of the most useful documents you will receive — if you know how to read it. This guide from Aritech Nanomaterials India explains the common sections.

1. Identification

Check the product name, catalogue or SKU number, batch/lot number, and date of manufacture or analysis. The batch number on the COA should match the label on your container. Keep the COA with your lab records — reviewers and auditors may ask for it.

2. Purity

Purity is usually given as a percentage (for example 99.9%, also written “3N”). Note the basis: is it trace-metals basis, metals basis, or overall chemical purity? A powder can be 99.99% on a metals basis and still contain surface oxide or adsorbed moisture.

3. Particle size

Particle size can be reported in different ways, and they are not interchangeable:

• APS from TEM/SEM: the size of individual primary particles seen under the microscope.
• DLS (hydrodynamic size): size in a liquid, including any agglomerates and the solvation layer — usually larger than TEM values.
• Laser diffraction (D10/D50/D90): common for micron powders; D50 is the median.
• Calculated from BET surface area: an equivalent spherical size.

When comparing suppliers or batches, compare the same method.

4. Specific surface area (SSA)

Reported in m²/g, usually by BET nitrogen adsorption. Higher SSA generally means smaller particles or more porosity. For catalysts, adsorbents and MOFs it is often the most important number.

5. Morphology and phase

Look for shape (spherical, irregular, rods, flakes) and crystal phase — for example anatase vs rutile TiO₂, or the crystal structure confirmed by XRD. Phase can change properties dramatically.

6. Impurity analysis

Many COAs list individual impurity elements in ppm, measured by ICP or similar techniques. If your application is sensitive to a specific element (for example Fe in catalysis or Na in electronics), check that line rather than the overall purity.

7. Appearance and other tests

Colour, form, moisture content, pH (for dispersions), concentration and viscosity may also be listed.

What to do when the material arrives

1. Match the batch number on the bottle and the COA.
2. Check the seal and packaging condition; photograph any damage and report it promptly.
3. Store as directed on the SDS.
4. If results matter for a publication, consider an independent check of the key property (e.g. XRD or particle size).

Need a COA or SDS for a product on our site? Ask sales@chemazone.in with the product name.