COAs (Certificates of Analysis) should help you verify what you’re receiving and whether it fits your process, not serve as marketing wallpaper. Here’s how to read them for silica, activated alumina, clays, and activated carbon.
Manufacturer COA vs Third-Party COA
Manufacturer COA
Issued by the original producer, tied to a specific lot with internal QC methods.
- Lot/batch ID (traceable to production records)
- Methods and typical spec ranges
- Represents the actual shipped lot (if matched)
Third-Party COA
Independent lab results. Useful for verification or tests the producer doesn’t run, but only if sampling and lot identity are clear.
- Explicit sampling method and date
- Test methods and detection limits (LOQ/LOD)
- Clear link to the same lot you’ll receive
Lot Identity & Sampling
- Lot/batch ID must match your receiving documents. If it doesn’t, you’re not verifying the right material.
- Sampling: Was it composite or grab? From which containers? Who sampled - vendor, lab, or you?
- Methods: Look for referenced standards or validated procedures - not ambiguous test names.
Key Specs: What to Look For
Silica & Alumina
- Surface area (BET, m²/g)
- Pore structure (if provided)
- Moisture / Loss on drying
- pH (slurry/water)
- Bulk density
Clays
- Moisture / LOI
- Acid activation (if applicable)
- Particle size / mesh
- pH
- Bulk density
Activated Carbon
- Iodine number or CTC activity
- Surface area (if provided)
- Hardness (abrasion number)
- Ash, moisture
- Particle size (GAC/PAC/pellet)
Across All Media
- Spec ranges vs single numbers
- Method references and units
- Lot ID printed on COA and shipping docs
- Supplier contact and issue date
Red Flags
- COA that isn’t linked to your lot (or no lot at all)
- Invented or undefined metrics (“proprietary” numbers with no method)
- Cherry-picked third-party tests with unclear sampling
- Renamed materials with hidden origin or continual rebagging
Requesting the Right Documents
Ask for:
- Manufacturer COA for the same lot you’ll receive
- SDS and TDS that match the product code/grade
- Third-party tests only when useful - include sampling notes, methods, and detection limits
When to Ask for Alternatives
If a grade is tight or the COA raises questions, request options with similar mechanisms and spec windows. We’ll provide candidates and note pack sizes and lead times.
Need a quick COA review or options?
Email info@sorbentsdirect.com with your goal, flow rate, and preferred pack size. We’ll reply with a short list and lead times.
Related collections: Silica · Activated Alumina · Clays · Activated Carbon
FAQ
Is a third-party COA required?
Not always. It can be useful, but it should complement never replace lot-matched manufacturer documentation.
What if the COA shows a single number?
Ask for the acceptable range and method. Ranges help you plan trials and understand variability.
Can you help compare two COAs?
Yes. Share both docs and your process goals; we’ll highlight differences that matter and suggest trial candidates.
