COA versus SDS: different documents, different jobs

Two documents travel with most laboratory materials, and they are often filed together, requested together and confused with each other. A certificate of analysis and a safety data sheet look similar from a distance: both are formal, both name the material, both come from the producer. They answer unrelated questions, and a file that holds one where the other belongs has a gap that no one notices until someone needs it.

What a safety data sheet is for

A safety data sheet describes the hazards of a substance or mixture and how to handle, store, transport and dispose of it safely. Under the Globally Harmonized System of Classification and Labelling of Chemicals, it has sixteen sections in a fixed order:

1. Identification
2. Hazard identification
3. Composition and information on ingredients
4. First-aid measures
5. Fire-fighting measures
6. Accidental release measures
7. Handling and storage
8. Exposure controls and personal protection
9. Physical and chemical properties
10. Stability and reactivity
11. Toxicological information
12. Ecological information
13. Disposal considerations
14. Transport information
15. Regulatory information
16. Other information

Its audience is everyone who handles, stores, moves or disposes of the material, and the emergency responders who may have to deal with it. It is written for the product, not for a particular lot. Two lots of the same material carry the same safety data sheet. It changes when the classification, the composition or the regulations change, and its revision date records when that last happened.

What a certificate of analysis is for

A certificate of analysis reports the results of testing on one lot. It names the material and the lot number, lists the tests performed against a stated specification, gives each measured result beside its limit, and carries a test or release date and a signature. Its audience is the person deciding whether this lot is fit for its intended use. A new lot means a new certificate, because the results are the results for that lot and no other.

Where the safety data sheet says what the material is and how it behaves in general, the certificate says what this particular container was found to contain.

Where they get confused

The most common confusion runs through Section 9 of the safety data sheet. That section lists physical and chemical properties — appearance, melting point, solubility, sometimes a purity figure — and it can look like a specification. It is not. The values there are typical or reference values for the substance, given so that handlers know what to expect. They are not test results for any lot and are not a promise about the one on the shelf. A purchasing file that holds a safety data sheet as its quality evidence holds no quality evidence.

The reverse confusion is rarer and just as real. A certificate of analysis says nothing about hazards, protective equipment or disposal. A safety review that relies on certificates will miss what it needs.

Dates add a third confusion. The revision date on a safety data sheet can be years old and still current, because nothing has changed. The test date on a certificate should sit close to the date the lot was made or released, and an old date there can mean a retest is due.

How to file them

Because they answer different questions on different schedules, the two documents belong in different places. Safety data sheets live where handlers can reach them quickly, filed by product, with the current revision replacing the old one and the old one retained if the procedure requires it. Certificates live with the lot: in the receiving record, linked to the lot number on the container, kept for as long as any result made with that lot needs to be defended.

A receiving check that asks for “the paperwork” invites one document to stand in for the other. A check that asks for two named documents — the current safety data sheet for the product, and the certificate of analysis for this lot, with its lot number matching the label — catches the gap at the door.

When one document refers to the other

Some certificates note the safety data sheet revision in force, and some safety data sheets point to the certificate for lot-specific values. Those cross-references are helpful and do not merge the documents. Each still has to be present, current and readable on its own, because each will be read by a different person, at a different moment, for a different reason.