GC Area% vs. wt% on a C12–14 Alkyldimethylamine COA
2026-11-10
GC Area% vs. wt% on a C12–14 Alkyldimethylamine COA
Two certificates of analysis show “C12: 70.” One reports 70 GC area%, and the other reports 70 wt%. The numbers look identical, but each answers a different question. Before approving a sample or comparing two suppliers, check what the percentage represents.
Read the unit and the denominator
| COA entry | What the percentage represents |
|---|---|
| GC area% | The area of a chromatographic peak divided by the total area of the peaks included in the calculation |
| wt% | The mass of the component divided by the total mass on the stated reporting basis |
A gas chromatograph measures detector response. Different compounds can produce different responses for the same mass. To report a mass fraction from GC data, the lab needs a suitable quantitative method and a defined reporting basis. Ask whether the result uses raw peak areas, response factor corrections, or a calibrated mass measurement. openlab.help.agilent.com
The same run can produce two percentages
Suppose a chromatogram gives 700 area units for C12, 200 for C14, and 100 for other included peaks. C12 accounts for 70.0 area% across all three groups. If the lab reports the distribution within the C12 and C14 peaks only, C12 accounts for 77.8 area%. Both values come from the same run. The denominator changed.
If your specification sets a minimum combined C12 and C14 content, ask which peaks the lab included in its total. That detail tells you whether the COA result can be compared with your acceptance limit.
Agree on the reporting basis before sample approval
A surfactant manufacturer qualifying C12–14 alkyldimethylamine for an amine oxide line can use the chain distribution to compare incoming feedstock lots. The COA for the tertiary amine intermediate and the specification for the resulting amine oxide apply to separate materials. Google Patents
When requesting a sample or quotation from China Amines Co., Limited, share your target C12 and C14 ranges, the required reporting unit, and any limits on other chain lengths. Request a representative COA so your purchasing and quality teams can review the same reporting basis before placing an order.
Technical references
- NIST — Principles of Quantitation: Chromatography
- Agilent OpenLab — Chromatography Data Analysis Glossary