Zinc PCA CAS 15454-75-8 vs 68107-75-5: What Cosmetic Buyers Should Verify

A Zinc PCA quote can look straightforward until the specification, safety data sheet, and certificate of analysis show different CAS numbers. One document may identify CAS 15454-75-8, another 68107-75-5, and a third may list both under the same INCI name. That inconsistency deserves a question before approval, but it does not by itself prove that a supplier has sent the wrong material.

The key is to separate two jobs that are often conflated. INCI is the ingredient name used for cosmetic ingredient declaration; CAS is a chemical registry identifier. A public INCI-reference page lists both CAS numbers under Zinc PCA. PubChem’s chemical records make a more specific distinction: 15454-75-8 is associated with zinc bis(5-oxo-L-prolinato), while 68107-75-5 is associated with zinc bis(5-oxo-DL-prolinato). A buyer should therefore not treat the two identifiers as automatically interchangeable for a controlled raw-material specification. Ask the supplier to state which material is actually supplied, how its identity is established, and whether that identity matches your approved formula and regional documentation.

This guide is for cosmetic formulators, technical buyers, QA teams, and contract manufacturers qualifying Zinc PCA powder or a Zinc PCA-containing blend. It provides a document-by-document check, explains why “99%” alone cannot settle the question, and gives a concise request you can send before approving a new source.

What the two CAS numbers tell you—and what they do not

Public chemical registries distinguish a Zinc PCA entry associated with L-pyrrolidone carboxylate from one associated with DL-pyrrolidone carboxylate. The names on the registry records are meaningful identity clues, not marketing labels. However, cosmetic ingredient databases may group both identifiers under the INCI name Zinc PCA. This means the label name alone may not tell a buyer which stereochemical form a specific raw-material lot represents.

Supplier pages may compress the identity into “Zinc PCA, CAS 15454-75-8 / 68107-75-5.” Some technical sheets list both identifiers while describing the material as an L-PCA zinc salt. This alone does not establish whether the lot is L-form, DL-form, or a blend; the controlled specification and lot records must resolve that point.

Use the following interpretation as a screening aid:

The practical decision is not to reject every dual-CAS listing. It is to determine whether your product specification requires a specific form, whether the supplier’s identity evidence supports it, and whether the label, safety documentation, specification, and COA are internally consistent. If your current formula was qualified with a named grade or exact material identity, do not silently broaden that specification to “either CAS” during second sourcing.

Start with the target material in your approved specification

Before asking vendors to explain their paperwork, look at your own product file. Find the approved raw-material name, INCI, CAS number or numbers, manufacturer grade, internal material code, intended use, and the documents used during original qualification. Check whether stereochemistry was actually controlled or whether the original file simply copied a generic supplier listing.

If your specification only says “Zinc PCA, cosmetic grade,” it may not resolve the discrepancy. This does not mean the current material is defective; the purchasing description may simply be too broad for a controlled change. Have R&D and QA decide whether the formula requires a specific form or can accept either. The technical owner—not a marketplace title—should make that decision.

Also confirm the supplied format. A raw material sold as “Zinc PCA” can be a powder, aqueous solution, or a premix containing other ingredients. The INCI name can appear within a blend, so the product title does not prove the raw material is 100% Zinc PCA. Ask for the full composition and active-content basis for liquids, diluted grades, and proprietary mixtures. Do not apply a powder formula’s percentage directly to a solution without normalizing its stated content.

Read the COA by test name and basis, not by the headline assay

A COA is useful only when the test and reporting basis are clear. Zinc PCA documents may report PCA content, zinc content, water, pH of a defined aqueous solution, appearance, and contaminant results as separate fields. These values do not all mean “purity.” They measure different things.

For example, one public supplier lot COA reports PCA content of 71.9% against a 70.4–74.0% specification, zinc at 18.7% against 17.4–19.2%, and water at 10.1% against 8.5–11.5%. The supplier identifies PCA and zinc as separate analytical parameters. That is more informative than a bare “99%” claim, but it remains one supplier’s lot document and is not a universal Zinc PCA specification.

A different supplier technical sheet reports PCA content on a dry basis, zinc content, and water content as individual parameters. Dry-basis figures are not the same as as-received figures. If a lab result is 80% PCA on a dry basis and the material contains 10% water as received, a simple illustrative conversion is 80% × (1 − 0.10) = 72% PCA as received. This arithmetic does not replace the supplier’s method or certificate; it shows why two percentages cannot be compared until the moisture basis is aligned.

“99% purity” may refer to an assay method, chromatographic area, a commercial specification, or a copied listing attribute. Do not infer that it means 99% PCA by mass. Ask the supplier to define the test method, reference standard, calculation basis, and whether the reported result is as-is or dried basis. Then compare it with the metric controlled in your own specification.

Check these COA fields together:

• Identity: test method, result, and acceptance criterion; ask whether an identity spectrum or other confirmatory method is available.
• PCA content: assay method and whether the result is on a dry or as-received basis.
• Zinc content: method and basis; compare it with the grade specification rather than treating it as an assay substitute.
• Water or loss on drying: method and limit, since moisture changes as-received composition and storage risk.
• pH: concentration and preparation method, such as a stated percentage aqueous solution; pH values without test conditions are hard to compare.
• Impurities: limits and results for relevant heavy metals or residuals under your risk assessment and destination requirements.
• Lot traceability: product code, lot number, test date, and manufacturer identity.

A sample COA can screen a candidate, but does not prove a later shipment matches it. Before approval, request a lot-specific COA or agree which tests apply to each delivery.

Reconcile the CAS across the supplier document set

Put the current TDS, SDS, specification, representative COA, product label, and quotation side by side. Do not only compare their first-page product names. Look for the exact CAS and EC numbers, chemical or systematic name, formula where stated, grade, manufacturer, product code, and whether the document applies to powder or a blend. A document set may list both CAS numbers on one sheet and only one on another. That is a discrepancy to resolve, not an automatic rejection. Ask the manufacturer—not only the trading contact—to confirm in writing:

1. Which CAS identity corresponds to the material in the quoted product code and current lot?
2. Is the material the L-pidolate form, the DL form, or another specified composition? What evidence supports that description?
3. Why do some documents list both CAS numbers? Is this a cross-reference, a specification scope, or a document-control error?
4. Does the finished cosmetic ingredient declaration remain Zinc PCA for the material as supplied? If the product is a solution or blend, what are all components and their concentrations?
5. Will revised documents and labels carry one harmonized identity statement for the approved grade?

If a clerical error is confirmed, request corrected controlled documents. Keep the written explanation with the approval record; a verbal answer is inadequate for formulation files, audits, or change control.

Sourcing candidate for buyer review

One Alibaba listing for cosmetic-grade Zinc PCA is linked below as an RFQ starting point. It is a sourcing route, not evidence that the CAS identity in your approved file matches this offer — the document checks above still decide that.

A simple comparison before approving a second source

Use a two-column comparison for your current approved material and the proposed replacement. Fill the fields from controlled documents and mark missing data as “not stated”; do not infer it from a product title.

A second-source decision needs both documentary and formulation checks. If the CAS distinction is relevant to your formula or market, resolve it before bench work. If identity is acceptable, then evaluate solubility, pH behavior, color, odor, viscosity impact, and stability in the actual formula. A matching INCI or CAS does not establish identical performance, and a formulation trial does not repair missing material identity documentation.

When “same INCI” is enough—and when it is not

For ingredient declaration, the INCI name is the field used in the cosmetic ingredient list. But the European Commission describes CosIng as an information database and explicitly cautions that an ingredient’s appearance in CosIng does not itself mean it is approved for use; legal conditions come from the applicable regulation. In procurement, the INCI therefore helps identify the declaration name, while the controlled specification and destination-market review establish what you are actually buying and how it may be used.

For low-risk exploratory bench work, a supplier’s Zinc PCA powder may be screened using a representative sample if the uncertainty is documented and the material is not released into production. For a commercial formula, customer-specific standard, or second-source approval, require a resolved identity statement and a document set that matches the raw material. If a customer specification explicitly names CAS 15454-75-8, do not substitute a product documented only as CAS 68107-75-5 without written technical approval, even if both appear under the INCI Zinc PCA in a public cosmetic ingredient reference.

This is especially important when a finished product’s regulatory file, safety assessment, and supplier change records rely on the raw material identity. The effort to reconcile a CAS difference is modest compared with reformulating or rebuilding a dossier after the material has already entered production.

What to include in your RFQ

A clear RFQ makes supplier responses comparable. Specify target identity, application, powder versus solution, INCI, accepted CAS identifiers, assay basis, pack size, sample quantity, destination, and requested documents. Ask whether each statement is manufacturer-issued, distributor-transcribed, or from a third-party test.

You can use this wording:

Please quote your cosmetic-grade Zinc PCA for [intended application]. State the exact supplied form, manufacturer product code, INCI, CAS and EC numbers, and whether the material is the L-pidolate form or another defined composition. Provide the current controlled TDS, SDS, representative COA, test methods, PCA and zinc assay basis, water specification, pH test conditions, and lot-traceability process. If your documents list both CAS 15454-75-8 and 68107-75-5, explain the relationship for this exact grade and confirm which identity applies to the offered lot.

Do not ask a supplier to certify a specification it has not tested. If the manufacturer cannot provide a stereochemical or identity distinction relevant to your requirement, record the field as not confirmed and decide whether the candidate can be used for development only or should be removed from the approved-source list.

References

1. PubChem. “Zinc pidolate,” CAS 15454-75-8; record describes zinc bis(5-oxo-L-prolinato). https://pubchem.ncbi.nlm.nih.gov/compound/Zinc-PCA
2. PubChem. “Bis(5-oxo-DL-prolinato-N1,O2)zinc,” CAS 68107-75-5. https://pubchem.ncbi.nlm.nih.gov/compound/Bis_5-oxo-DL-prolinato-N1_O2_zinc
3. U.S. FDA Substance Registration System. “Zinc Pidolate,” UNII C32PQ86DH4. https://precision.fda.gov/uniisearch/srs/unii/C32PQ86DH4
4. European Commission. “Cosmetic ingredient database (CosIng).” https://single-market-economy.ec.europa.eu/sectors/cosmetics/cosmetic-ingredient-database_en

Commercial reference and supplier-document examples reviewed: SpecialChem Zinc PCA INCI index; Cosmate® ZnPCA technical data sheet; Handymade Zinc PCA lot COA and product TDS. These illustrate reference or supplier-specific information and are not universal specifications.