A Certificate of Analysis for diethyl oxalate should help the buyer decide whether a specific batch is suitable for the intended process. It should not be treated as a decorative attachment to a purity claim. For CAS 95-92-1, a practical review starts with identity and assay, then examines parameters that can affect reaction performance, storage, appearance and purification.
Confirm identity before comparing numbers
The COA and specification should identify diethyl oxalate and CAS 95-92-1. Public databases list the molecular formula as C6H10O4, molecular weight as 146.14 g/mol and EC number as 202-464-1. Product name, batch number, production or test date and document approval should be clear. If synonyms such as ethyl oxalate or oxalic acid diethyl ester are used, the CAS number helps prevent confusion with related oxalates.
Assay needs a method and basis
A value such as ≥99.5% is meaningful only when the analytical method and reporting basis are understood. Gas chromatography is commonly considered for organic purity profiles, but the buyer should confirm the supplier’s actual method, integration rules and treatment of unidentified peaks. Assay alone may not capture water or nonvolatile material, so it should be reviewed alongside the rest of the specification.
Why moisture and acidity matter
Water can be important in hydrolysis-sensitive storage and in reactions that require controlled moisture. The acceptable level depends on the process rather than a universal purchasing rule. Acidity can indicate acidic components or degradation-related concerns and may affect catalyst consumption or downstream neutralization. Buyers should state a method and limit when these parameters are critical instead of assuming every supplier uses the same test.
Appearance, color and residue
Appearance provides a quick receiving check but cannot replace analytical testing. A buyer may review clarity, visible contamination and color against an agreed method. Nonvolatile residue can matter when material is distilled, recovered or used in a process sensitive to high-boiling impurities. Density or distillation-related data may also be requested when they support receiving verification or process control.
A practical COA review table
| Parameter | Buyer question |
|---|---|
| Identification | Does the document clearly match CAS 95-92-1 and the ordered grade? |
| Assay | Which method and reporting basis were used? |
| Moisture | Is the limit compatible with the reaction and storage plan? |
| Acidity | Could the reported level affect catalyst demand or downstream work-up? |
| Color/appearance | Are the method and acceptance criteria defined? |
| Residue/impurities | Which related compounds or nonvolatile materials are relevant? |
Compare suppliers on equivalent terms
Do not compare only the largest purity number. Compare grade, test method, sampling point, batch traceability, package condition and the supplier’s process for handling deviations. Request a recent representative COA before approving a supplier and a batch-specific COA with the shipment. If the application has strict requirements, agree on them in the purchase specification before production or dispatch.
For current commercial information, visit the Diethyl Oxalate CAS 95-92-1 product page and include the required test items in the inquiry.
Reference sources
Public identity data is available from PubChem and ECHA. Numerical acceptance limits should come from the agreed supplier specification, current batch COA and the buyer’s validated process requirements.