What HPLC purity means
HPLC stands for high-performance liquid chromatography. It separates components under a defined set of analytical conditions. When a peptide report gives an HPLC purity result, read it as a result from that method, not as a complete description of everything in the vial.
The useful question is what the laboratory measured and how it calculated the reported value. Two large percentages printed on two product pages are not enough information for a sound comparison.
Read the calculation
An area-based result commonly compares the area assigned to the target peak with the total area of the peaks included in the calculation. That is a comparison of detector responses. It is not automatically a measurement of the target compound's mass as a fraction of the entire sample.
Check whether the report actually says area percentage. If it uses another calculation, ask for the definition instead of assuming the familiar one. Record any stated exclusions and whether the chromatogram and integration information are available.
Give each number its own column
A review sheet becomes much easier to read when different quantities have separate headings. Do not put a label claim, an analytical percentage and a measured content result into a single column called purity.
| Record | Example of the field to copy |
|---|---|
| Labelled amount | The nominal amount printed on the container |
| Analytical result | The percentage and its stated calculation |
| Measured content | The amount and units reported by the laboratory |
| Method | Method identifier, detector information and report notes |
| Sample | Sample identifier linked to the report |
This worksheet is a record format, not a worked laboratory result. It contains no measured values for EPS products. Leave a cell empty when the document does not provide the information, and add a question in the review notes.
Ask what the method distinguishes
ICH Q2(R2) describes validation characteristics such as specificity, accuracy and precision. These help frame questions about whether a procedure is suitable for its intended analytical purpose. The reference does not validate an unnamed method on a supplier's website.
Ask the issuing laboratory how the target is distinguished from relevant other components and what the result is intended to establish. Avoid making that judgement from the visual height of a single peak. A screenshot can omit the method, calculation and surrounding report notes.
Compare equivalent records
Before comparing reports, align the sample description, method and units in your worksheet. If one report provides only an area percentage and another also reports milligrams, keep those differences explicit. More columns of data do not make the two original measurements interchangeable.
The same applies to dates. A newer PDF may be a revised document rather than a newly analysed sample. Record the analysis date and the document revision separately, and ask which event changed when the distinction is unclear.
Link the result to the batch
A carefully read analytical result still needs to be connected to the relevant material. Follow the COA reading checklist to record the sample and lot identifiers, then consult the report library for current publication status.
Keep the interpretation beside the original report. A colleague should be able to see the reported number, the source of that number and the limits you recorded without relying on a product headline or a recollection of a conversation.
