Purity and content answer different questions

The quick distinction

Chromatographic purity describes how much of the detector's integrated response is associated with the principal peak under a stated separation method. Content or assay describes an amount of analyte measured in the submitted sample, using a method designed and reported for that purpose. One concerns the relative signal profile; the other concerns quantity.

A material can have an area-percent purity result without a measured milligram result. Report only the conclusion the laboratory actually issued.

What area-percent purity measures

In chromatography, components are separated and recorded as peaks by a detector. Area-percent purity usually compares the integrated area of the principal peak with the total integrated peak area included by the stated method. The number depends on separation conditions, detector response, integration choices, and the compounds the method can detect.

That percentage is not a direct statement of milligrams per vial, net content, sterility, endotoxin status, human-use safety, or efficacy. It does not prove peak identity without an appropriate identity assessment.

Why a percentage does not specify mg per vial

Area percent is a ratio of detector responses, not a balance reading or calibrated amount by itself. Converting it into milligrams would require information and a validated quantitative approach that an area-percent result alone does not supply.

A content or assay result should state the sample, reported amount and unit, method, and conclusion scope. The unit might describe mass per submitted item, concentration, or another quantity. Never substitute a label claim or purity percentage for a missing measured-content result.

Raw material and finished-vial scope

Sample description controls interpretation. A supplier raw-material result characterises the submitted raw material; it does not establish the measured contents, fill consistency, sterility, or endotoxin status of every finished vial. A finished-vial test also applies only to its submitted sample and listed tests.

Supplier internal quality control and independent laboratory testing are different sources. ATMI presents each according to its origin. An ATMI batch ID, supplier lot ID, and independent report or accession number may differ; the order documentation and batch record provide the explicit mapping.

Five-point report checklist

Before recording a result, check the report as a complete record rather than extracting the largest number on the page.

• Confirm the issuing laboratory, sample description, and report or accession number when available.
• Follow the explicit mapping among the ATMI batch ID, supplier lot ID, and laboratory identifier; do not require identical strings.
• Identify the method and detector, then distinguish identity, area-percent purity, content or assay, and microbial testing.
• Record the result with its unit, report date, and stated limitations. A date alone neither validates nor invalidates a report.
• Treat unlisted tests as unknown. Do not infer content, sterility, endotoxin status, safety, or efficacy from a purity result.

Continue reading

The COA guide explains common report fields and identifier mapping. The compound-testing guide compares analytical questions and documentation sources. ICH Q2(R2) is included below solely as general analytical-method guidance; it is not an ATMI endorsement, certification, or claim that a particular report followed that guidance.

• How to Read a Certificate of Analysis →
• Research Compound Testing →
• FDA overview: ICH Q2(R2) Validation of Analytical Procedures → — general analytical-method guidance