CAS Number vs EC Number: Which Identifier to Store and Why

Enriching a catalog that contains chemicals, lubricants, adhesives, cleaning agents, or treated industrial goods means navigating two substance identifiers that look interchangeable on a safety data sheet but serve entirely different downstream jobs. When a CAS number ends up in an EC number column — or both get collapsed into one free-text field — automated SDS retrieval breaks, REACH screening fails silently, and cross-supplier deduplication loses its anchor. Claro resolves and validates both identifiers across supplier feeds, enriches missing fields from authoritative sources, and writes clean records back into your PIM or ERP with a source trail attached to every attribute.

A CAS Registry Number is assigned by the Chemical Abstracts Service and acts as a near-universal key for a specific substance across scientific literature, SDS authoring, and supplier specifications. An EC Number (European Community number) is a regulatory identifier used inside EU chemical legislation, drawn from inventories such as EINECS, ELINCS, and the NLP list. A distributor selling a thread-locking adhesive or a degreaser will often see both printed on the same SDS — which is exactly why teams conflate them, and why keeping them in separate, validated columns matters.

At a glance

Both identifiers carry a trailing check digit, so a validation pass can catch transcription errors in either column before they reach a regulator or a customer portal.

Before and after: messy vs. trusted substance data

The difference between a single mixed field and two validated columns sounds minor until you trace the downstream failures.

When to use each

CAS Number

Store the CAS number when your priority is identity and enrichment. Because it is the most widely referenced substance key, it is the strongest join field when you reconcile the same product across multiple supplier feeds, an MRO marketplace listing, and a manufacturer datasheet. If you are deduplicating an industrial-distribution catalog or matching a private-label cleaner back to its formulation, the CAS number is usually the anchor that survives across sources. It is also the lookup most SDS databases and chemical registries expect.

EC Number

Lead with the EC number when the job is EU regulatory compliance. REACH registration, CLP labeling, and customs paperwork are organized around it, so a furniture importer documenting a wood treatment or a CPG brand shipping a household chemical into the EU needs the EC number populated and correct. It does not, however, cover every substance you can buy, and a single CAS entry can map to more than one regulatory listing, so it is a poor universal join key for catalog matching.

The common failure mode

The failure mode is treating these as one free-text field. When a buyer pastes 231-791-2 into a CAS column, automated SDS retrieval and REACH screening both fail quietly — no error, just a blank result. Validating each identifier against its own format and check digit, and recording where the value came from, prevents that silent breakage.

This is the same provenance discipline that keeps any AI- or vendor-supplied attribute trustworthy at scale. Claro applies format validation, check-digit verification, and source-linked enrichment to substance identifiers as part of its standard enrichment pipeline, then writes the corrected values back into your existing PIM or ERP fields without manual intervention.

Related

FAQ

Is a CAS number the same as an EC number? +

No. A CAS number is a global substance key issued by the Chemical Abstracts Service and used for lookups, SDS authoring, and cross-supplier matching. An EC number is an EU regulatory identifier drawn from inventories like EINECS and ELINCS, used for REACH and CLP compliance. They use different formats and often both appear on the same safety data sheet.

Can you convert a CAS number to an EC number? +

Often, but not always, and not by reformatting. The mapping comes from regulatory inventories, and one CAS number can correspond to more than one regulatory listing or to none at all. Treat conversion as a lookup against an authoritative source, not a calculation, and store both values rather than deriving one on the fly.

Which identifier should a distributor store in the catalog? +

Store both in separate, validated fields. Use the CAS number as your matching and enrichment anchor across supplier feeds, and the EC number for EU compliance and customs documentation. Keeping them in distinct columns with a documented mapping avoids the silent failures that happen when one free-text field mixes formats from different sources.

Does every chemical have both a CAS and an EC number? +

Most established substances have a CAS number, but EC numbers only cover substances on the relevant EU inventories, so newer or non-EU substances may lack one. That asymmetry is why the CAS number is the stronger universal join key for catalog matching across mixed supplier feeds.

How do I check whether a CAS or EC number is valid? +

Both identifiers end in a check digit you can verify against the published algorithm, which catches most transcription errors before they reach a regulator or marketplace. Run format and checksum validation during feed onboarding rather than after records have already published to a customer portal.

How does Claro handle CAS and EC number enrichment? +

Claro resolves substance identifiers across supplier feeds, validates CAS and EC values against their respective check-digit algorithms, enriches missing fields from authoritative sources, and writes clean, source-linked records back into your PIM or ERP. Every populated attribute carries a confidence score and a source trail so you can audit any value at the field level.