Reading a Chinese Chemical COA: Test Methods, Raw Data, and What Each Parameter Actually Proves

Mon, 07 Sep 2026 · HARMONY TECHNOLOGY (ZHEJIANG) CO., LTD.

Reading a Chinese Chemical COA: Test Methods, Raw Data, and What Each Parameter Actually Proves

The short version：A certificate of analysis is only as strong as the method behind each number. A COA that lists measured values with methods and limits is verifiable evidence; one that says “conforms” is a claim. This guide explains what each common parameter on a Chinese chemical COA is actually measuring, which analytical method produces it, and how to tell a raw-data COA from a restated one.

1. Purity / Assay — GC-FID (or GC-TCD for permanent gases)

What the number is: the mass fraction of the target compound, reported as area-% or mass-% — these are not the same thing, and Chinese COAs frequently omit which basis was used.

Method: gas chromatography with flame-ionization detection (GC-FID) is standard for R134a, R22, R32, DCM, and most chlorinated solvents; thermal conductivity (GC-TCD) is used where FID response is weak.

What to look for on the COA:

Practical check: for refrigerants, moisture and non-condensable gas (NCG) limit real-world performance far more often than the assay figure does — yet they are frequently the fields left off a two-line COA.

2. Water Content — Karl-Fischer Titration

Method: coulometric KF for low-ppm work (<100 ppm), volumetric KF for higher ranges.

Typical limits: refrigerants ≤10 ppm (often ≤5 ppm); technical-grade DCM ≤0.05 % (500 ppm); solvent / industrial grade ≤0.02 % (200 ppm); pharmaceutical grade ≤0.01 % (100 ppm) — the same three-grade table used in the DCM specification article, and the only grade table we quote.

What the number proves: water is the single most common cause of acid formation and system corrosion in refrigeration circuits. A ppm figure is only meaningful alongside the sampling point (cylinder valve vs. bulk tank) — KF results shift with handling, so an unqualified “8 ppm” tells you little without knowing where the sample came from.

3. Acidity — Titration (HCl equivalent)

Method: acid-base titration, expressed as ppm HCl, or as mg KOH/g (acid value).

Why it is on a refrigerant COA at all: residual acidity predicts lubricant degradation and metal attack in a running system. Limits are typically ≤1 ppm (HCl) for refrigerant grades. What water and acidity actually do inside a POE system — hydrolysis, free fatty acids and copper plating — is worked through in R134a system compatibility.

Common gap: acid value is often reported as a single figure with no statement of indicator or potentiometric endpoint. Potentiometric titration is less operator-dependent — worth asking which was used when results hover near the limit.

4. Water Content vs. Non-Condensable Gas — Distinguish Them

Both degrade performance; both appear as “moisture-related” complaints. They are measured differently:

A COA listing “moisture” without clarifying water vs NCG is ambiguous — the two have different causes (handling vs. filling/vacuum process) and different fixes.

5. Residue / Evaporation Residue — Gravimetric

Method: evaporate a weighed sample, dry to constant mass, weigh the residue.

What it proves: non-volatile contamination (lubricants, particulates, high-boilers). For solvent grades it is stated as ≤10–50 ppm; for refrigerant grades it is usually absent because the product is distilled, but its absence from the COA is not the same as a passing result — if it is not listed, it was not tested, and that should be stated as such.

6. Batch Number ↔ Drum Label ↔ COA: the Consistency Chain

The only way a COA becomes evidence rather than paperwork is a three-way match:

COA batch number  ==  drum/cylinder label  ==  shipment packing list line

What breaks the chain in practice: a COA covering a production batch while the shipment is a repackaged lot. This is not necessarily fraud — but it changes who issued the QC record (producer’s lab vs. filler’s lab), and the COA should say which.

Practical verification: ask for the labels of two drums within the same shipment — batch numbers that differ across one shipment are normal for repacked product and should be reflected as separate COA lines.

7. COA ↔ MSDS ↔ Regulatory Filing: cross-document arithmetic

A COA is a batch document; an MSDS/SDS is a product document; a REACH registration or F-gas quota filing is a company/volume document. The three must be arithmetically consistent:

8. What a COA Cannot Tell You

Technical literacy includes knowing the document’s limits:

• It is a sample, not the shipment — it certifies the batch the sample came from, under the condition the sample was taken.
• It does not certify packing integrity — no COA field reports valve torque, cylinder hydrostatic test date, or linings. Those live in UN packaging marks and periodic inspection records.
• It does not certify origin compliance — origin, quota consumption, and destination-market admissibility are separate filings.

Technical reference for importers and QC engineers. Product grades, limits and quota treatment vary by destination market and by year — figures above are stated as commonly published specification ranges, and current quota/phase-down values should be taken from the applicable regulation for the year of shipment.

What we can provide

On request we can return the records behind the certificate rather than a restated one:

• Measured values with methods — assay (GC-FID), water (Karl-Fischer, coulometric or volumetric), acidity (titration to a stated endpoint) and residue on evaporation (gravimetric), each with its limit, its result as measured, and the method used.
• Raw records — the chromatogram and integration parameters behind the assay figure, and the titration record behind the water figure, where the testing laboratory retains them.
• Sampling point and date — where and when the sample was taken (cylinder valve, bulk tank or line), since a Karl-Fischer figure is not comparable without it.
• Batch-to-label traceability — the batch numbers the certificate covers, matched against the drum or cylinder labels in the shipment; repacked lots are listed as separate certificate lines.

Contact us with: the batch numbers, and the two or three parameters that decide acceptance for your use.

Prepared by HARMONY TECHNOLOGY (ZHEJIANG) CO., LTD. — trading company; the group’s operating entity for this product line.