Reading an HPLC Purity Percentage and Chromatogram
Read HPLC peak area percentages, chromatograms and method limits. Learn what the remaining signal represents and why purity is not a milligram amount.
This guide is about the percentage and the chromatogram behind it. For the separate question of how much material was reported in a vial, use purity versus amount.
Begin with the laboratory’s result label and method. Do not assume every value called “purity” uses the same calculation.
Find the calculation basis
For an uncorrected HPLC area percentage, divide the target peak area by the total integrated peak area and multiply by 100. Waters distinguishes this from calculations using response-corrected areas. Ask which result the laboratory reports.
Area % = target peak area ÷ total integrated peak area × 100
This is a signal ratio under a stated method. It is not a weight measurement or a vial’s milligram amount.
Calculation reference: Waters: area and adjusted-area calculations.
Read the trace before comparing
Bachem describes analytical HPLC as a common peptide-purity method, with the main peak area compared with integrated peak areas. The displayed trace and method help explain what was counted.
- Locate the assigned target peak and the laboratory’s result table.
- Check that axes, the run interval, and labels are readable. Ask for the complete trace if a crop removes useful context.
- Ask what detection settings and integration rules were used when you need to compare methods.
- Keep unresolved peaks unresolved. A small peak is not an identified compound merely because it appears on a graph.
Method reference: Bachem: peptide quality control. This explains a general method; it is not a test report for PSL stock.
Compare percentages carefully
The remainder of an area-percentage calculation concerns the other integrated signals. It is not a complete inventory of the vial. Anything undetected, unresolved, or excluded from integration is outside that calculation.
More decimal places do not establish greater accuracy. Before ranking two batches, check whether their methods, calculation bases, and relevant reporting limits are comparable. If you lack that information, keep the results as separate reported values.
Identity, reported amount, and other tests answer different questions. See the three-result comparison and testing-scope guide.
What to keep with the number
Save the full original file, sample and batch name, task number, analysis date, result label, percentage, and available method notes. Keep unanswered questions in the same record.
For PSL’s published values, use the matching batch report. A reported value belongs to the tested sample; do not extend it to untested vials or later batches.
Research Use Only
This guide is for researchers and lab staff reviewing lab reports. Materials discussed are for laboratory research only. They are not for human or veterinary use.
Check our published batch reports
Every active catalog lot has a published Janoshik report. Peptide reports list tested-sample purity and reported amount; the solution report lists benzyl alcohol concentration. Open the original file and match the batch.
Examples of published reports
Each report covers the sample and lot named on that document. Materials are for laboratory research only.
Related Analytical Guides
Peptide Identity vs Purity vs Content: What Each Analytical Result Actually Tells You
Identity, purity, and content answer three different questions. Learn what each result means and how to read them together on a lab report.
What Does 99% Peptide Purity Mean? Purity vs Amount
Read purity, milligrams, and concentration as separate results, with published GHK-Cu, Tesamorelin, and solution report examples.
What Peptide Analytical Testing Can and Cannot Establish
What standard lab tests can show, what needs a separate test, and what a chemical report alone cannot prove.