L-Carnitine L-Tartrate COA: How to Read a 99% Assay and a 68% L-Carnitine Result

Quick Answer

Two different percentages on one L-carnitine L-tartrate certificate are usually not a contradiction. The salt is about 68% L-carnitine and about 32% tartaric acid by mass, so a salt assay near 99% and an L-carnitine result near 68% can describe the same pure material. What decides whether the lot is acceptable is which analyte each number measures, on what basis and by which method.

Write the purchase specification around the quantity your formula needs: L-carnitine content by weight, as-is or dried basis, with a named method. Keep the salt assay, the tartaric acid figure and any stereochemical evidence as separate lines, and do not let a headline percentage stand in for all of them.

The two assay numbers can both be right

A buyer sees “assay: 99%” on a quote, then opens the certificate of analysis and finds L-carnitine at 67.8%. Is the material short, mislabeled, or being described on two different bases? Often, the numbers refer to different things. L-carnitine L-tartrate is a salt made from levocarnitine and tartaric acid. A high result for the salt or overall assay can coexist with about 68% L-carnitine by weight because tartaric acid contributes to the remaining mass.

That does not mean every pair of numbers is automatically acceptable. A percentage without an analyte, method, calculation basis, and sample basis is incomplete. The buyer’s job is to find out what the laboratory measured and whether the contract specification calls for that same quantity.

Start with the identity of the salt

The common L-carnitine L-tartrate form is a 2:1 salt: two levocarnitine molecules associate with one tartaric acid molecule. The formula is C18H36N2O12 and the molecular weight is about 472.49 g/mol. The salt is also identified by CAS 36687-82-8 in compendial and regulatory materials. Check the specific material and its stereochemical identity: “carnitine tartrate” without the L designation may not be enough to describe the intended form.

Using molecular weights, the two levocarnitine units account for roughly 68.1% of the salt’s mass, while tartaric acid accounts for roughly 31.9%. That is the chemical reason a result near 68% L-carnitine is plausible for a highly pure L-carnitine L-tartrate ingredient. It is a theoretical composition check, not a substitute for a laboratory assay. In purchasing documents, use a fully specified name, CAS number, formula or reference standard, and intended grade [3].

Why “99% assay” is too vague to approve a lot

The word assay describes a measurement against a method and a defined analyte. It does not tell you, by itself, whether the result means L-carnitine L-tartrate, L-carnitine moiety, total carnitine, or a chromatographic area percentage. “99% by HPLC” can also refer to normalized peak area rather than mass fraction. Those are not interchangeable claims.

Ask the supplier to complete a sentence: “The 99.0% result is ___, measured by ___, calculated against ___, and reported on a ___ basis.” Possible bases include as-is, dried, or an explicitly stated salt-equivalent basis. If the vendor cannot answer, treat the marketing number as unverified, not as a pass. A method may quantify the L-carnitine component after extraction or derivatization, while a separate assay may measure a broader salt-related quantity.

A worked example: 99.3%, 67.8%, and 31.4%

Suppose a COA reports “assay (HPLC) 99.3%,” “L-carnitine 67.8%,” and “L-tartaric acid 31.4%.” The arithmetic of the last two values gives 99.2%. That near-total sum is chemically plausible for the two principal components of the salt. It does not prove that the first line was calculated as the sum of the latter two; the supplier must confirm the method and calculation.

The buyer should record each line separately rather than replacing them with one headline percentage. Ask whether 67.8% is reported on an as-is or dry basis, what test measures tartaric acid, and what “assay (HPLC)” counts. Confirm whether rounding explains a 0.1-point difference and whether the contract permits the stated values. If water is measured separately, do not silently correct one figure to match another unless the agreed method requires moisture correction.

Use a named analyte and a named basis in the purchase specification

The safest specification defines the number the buyer actually needs. For example, state a minimum or range for L-carnitine content as a percentage by weight, identify whether it is as-is or dry basis, and name the applicable method or validated equivalent. If you also need a total salt assay or chromatographic purity, list it as a separate requirement with its own method and limits.

Avoid contracting on “99% purity” alone. It leaves room for a supplier to quote a chromatographic area result when the buyer expects a mass assay. It can also lead a quality team to reject a compliant salt simply because the L-carnitine moiety is not 99% of the salt mass. Align the quotation, specification, purchase order, and incoming test plan before the first commercial order.

What a useful COA should let you verify

At minimum, the document should identify the manufacturer or responsible site, product name, lot or batch number, manufacturing or retest date, test date, specification, actual result, unit, test method, and authorized approval. The batch number should match the shipping label and any sample used for qualification. A generic “typical COA” is not evidence that the delivered lot passed.

For this salt, review identity, L-carnitine content, tartaric acid content if specified, water or loss on drying, appearance, and relevant impurity or contaminant limits. Depending on the application and jurisdiction, microbiological criteria, residual solvents, elemental impurities, and other controls may matter. Do not assume that a test was performed because a supplier’s brochure displays a certificate icon. Ask for the lot-specific report and method details.

A specification can be narrower than a regulatory or compendial example when the buyer has a justified process need.

Check method suitability before comparing results

Two laboratories can report different values without either one making an arithmetic mistake. They may use different extraction conditions, reference standards, detectors, calculations, or moisture corrections. Results from an acidimetric titration are not automatically comparable with an HPLC area percentage. Even two HPLC methods can differ if one separates related compounds and the other only integrates a main peak.

When qualifying a supplier, request the method name or a method summary, the reference standard, reporting basis, and whether the laboratory is internal or third-party. If the buyer’s incoming method differs from the supplier’s release method, run a method comparison or establish a reasonable correlation before setting a rejection rule. For a disputed lot, preserve a sealed sample, agree a referee laboratory, and write down which method governs before the result is known.

Do not let moisture correction hide a failed result

A dry-basis value is higher than an as-is value when a sample contains moisture, because the calculation removes water from the denominator. This can be appropriate when the method or specification calls for it. But it must be explicit. A supplier should not present a dry-basis result as if it were the as-is content received by the formulator.

For example, the report should state “L-carnitine, 67.8% as-is” or “67.8% on dried basis,” rather than just “67.8%.” If water is 0.4%, a dry-basis correction may move the reported number slightly upward; it does not turn a salt into 99% L-carnitine. The identity and component mass balance remain separate questions. When comparing an incoming test with a release COA, first normalize both results to the same basis using the agreed procedure.

Stereochemistry and identity need their own evidence

L-carnitine is the biologically relevant L form, while a general assay may not distinguish it from the D enantiomer or related compounds. A result that shows the expected total peak or total carnitine does not necessarily establish the required stereochemical profile. This matters when the product specification explicitly requires levocarnitine identity or a limit on D-carnitine.

Ask which identity tests are performed and whether the chosen method resolves the relevant enantiomers. Look for a stated acceptance criterion and an actual result, not only a phrase such as “meets USP.” If a supplier claims compendial compliance, request the grade, monograph edition or current reference, and supporting batch documentation. A certificate logo is not a substitute for the underlying release data. Also verify that the COA belongs to L-carnitine L-tartrate, not L-carnitine base, acetyl-L-carnitine, fumarate, or a finished capsule blend.

Commercial listing for an initial inquiry

The listing below is a starting point for a quote request, not an endorsement or verification of the supplier’s manufacturing controls. Its page title identifies L-carnitine L-tartrate and the linked page resolves to an Alibaba product detail page. The public supplier summary reports six years on the platform. Before ordering, ask for a current specification, a lot-specific COA, method and basis for every assay figure, sample, and clarification of whether the seller is the manufacturer or a trading company. Product availability, pricing, shipping and commercial terms can change.

Reading limits in a regulatory or compendial source

An FDA GRAS notice for a specific intended use describes L-carnitine L-tartrate as approximately 68% L-carnitine and 32% L-tartaric acid. The notice includes an example specification with L-carnitine content of 67.2–69.2% on a dry basis and tartaric acid content of 30.8–32.8% on a dry basis. These ranges help explain the mass composition and offer a useful comparison point for a buyer [1].

They are not automatically the right acceptance limits for every product. The notice concerns a particular ingredient and intended use; it is not a blanket approval for all markets, grades, doses, or finished products. The supplier’s actual declared specification and the buyer’s legal obligations still need review. Treat the source as evidence for what that filing says, not as a universal certificate of compliance. The same caution applies to compendial texts.

A practical incoming-lot decision sequence

When a delivery arrives, first match the product and lot identifiers across the purchase order, packaging, and COA. Next compare the stated specification and actual results, preserving units and basis. Then resolve any ambiguous assay labels with the supplier in writing. A value that looks low may be the correct L-carnitine fraction of the salt; a value that looks high may be a peak-area result rather than a mass fraction.

If the name, CAS, salt form, method, or batch identity conflicts, quarantine the lot while the supplier clarifies. If the chemistry is coherent but the COA omits method or basis, request a corrected or supplemented document before approving release. If the result is outside the agreed limit, follow the quality agreement’s deviation and retest process rather than averaging a passing supplier number with a failing incoming number.

Questions to send with a quote request

A short, specific request usually produces more useful documents than asking for “COA and best price.” Ask the supplier to confirm the exact chemical name and CAS; whether the offered product is L-carnitine L-tartrate rather than another carnitine form; the declared L-carnitine percentage and its as-is or dry-basis status; what the quoted 98% or 99% assay represents; the method and reference standard; and whether the sample COA is from a real batch or is only typical data.

Also ask for the specification sheet, lot-specific COA for the sample or production batch, country of manufacture, packaging and shelf-life conditions, and available quality documents relevant to your intended market. Ask how a change in site, process, or test method is communicated. For price comparison, compare the cost per unit of L-carnitine delivered, not just the price per kilogram of salt.

The takeaway for buyers

A salt assay near 99% and an L-carnitine result near 68% are not inherently contradictory. The first may describe a broader assay or chromatographic purity; the second may describe the L-carnitine portion by mass. The chemical composition makes a value near 68% plausible, while the exact release decision depends on the method, basis, lot, and contract specification.

Write the purchase specification around the analyte your formula needs. Require the supplier to name what each percentage measures and whether it is as-is or dry basis. Review identity and stereochemistry separately from assay; review moisture and contaminants separately from chromatographic purity. When those details are missing, pause approval and request them instead of guessing from the headline number. That small clarification at quotation stage can prevent a false rejection, an incorrect formulation calculation, or an expensive dispute after delivery.

References

1. U.S. Food and Drug Administration. GRAS Notice No. 993, L-carnitine-L-tartrate. Composition and example specifications for the notified intended use. Source
2. U.S. Food and Drug Administration. GRAS Notice Inventory, GRN 000993. Source
3. United States Pharmacopeia. Food Chemicals Codex, l-Carnitine l-Tartrate monograph entry, formula and molecular weight. Source
4. United States Pharmacopeia. Draft USP-NF monograph materials for L-Carnitine L-Tartrate. Verify current official status before contractual use. Source
5. Food Standards Australia New Zealand. Application A1102 supporting material, published specifications and analytical methods for L-carnitine L-tartrate. Source