How to Read HPLC Results for Peptides

Written by the AllMyPeptides Research Team

Understanding HPLC Chromatograms

An HPLC chromatogram is a graphical output from High-Performance Liquid Chromatography analysis. The x-axis represents time (how long compounds take to pass through the column), and the y-axis represents detector response (how much of each compound is present).

Each peak on the chromatogram represents a different compound in the sample. The position of the peak (retention time) identifies the compound, while the area under the peak indicates its relative quantity.

The Main Peak

The main peak (also called the target peak) represents your peptide. It should be the tallest and largest peak on the chromatogram, appearing at a characteristic retention time. A sharp, symmetrical main peak indicates a pure, well-defined compound. Broad or tailing peaks suggest degradation or impurities.

Secondary Peaks

Secondary peaks represent impurities — either related peptides from incomplete synthesis, degradation products, or residual solvents. In a high-purity peptide (99%+), secondary peaks should be minimal — barely visible above the baseline. The total area of all secondary peaks combined represents the impurity percentage.

Reading the Purity Percentage

The purity percentage is calculated as:

Purity % = (Area of main peak / Total area of all peaks) × 100

For example, if the main peak has an area of 990,000 and all peaks combined have an area of 1,000,000:

Purity = (990,000 / 1,000,000) × 100 = 99.0%

At AllMyPeptides, we require 99%+ purity for all batches. This means the main peak must account for at least 99% of the total peak area. Batches below this threshold are rejected.

Red Flags to Watch For

When reviewing an HPLC chromatogram, watch for these warning signs:

Multiple large peaks: Indicates significant contamination or poor synthesis
Broad main peak: Suggests degradation or aggregation of the peptide
No peak at expected retention time: Wrong product or complete degradation
Missing chromatogram: The COA should include the actual chromatogram, not just a number
Purity below 95%: Unacceptable for research-grade peptides

If you have questions about interpreting your COA, contact our research support team.

Frequently Asked Questions

What does 99%+ HPLC purity mean?+

It means that 99% or more of the material in the sample is the target peptide, as measured by the area-under-curve method on HPLC analysis.

Can a peptide be 100% pure?+

In practice, no. Trace impurities from the synthesis process (deletion sequences, residual reagents) are always present at minute levels. 99%+ represents the practical upper limit for synthetic peptides.

What are the small peaks next to the main peak?+

Small adjacent peaks are typically related peptides from the synthesis process — either sequences missing one amino acid (deletion sequences) or sequences with extra amino acids. These are normal at trace levels.

Should I trust a COA without a chromatogram?+

No. A proper COA should include the actual HPLC chromatogram showing the peaks. A purity number without the chromatogram cannot be independently verified.

Products discussed in this guide are for research and laboratory use only. AllMyPeptides does not condone or support misuse of any research materials. Not for human or animal consumption.

How to Read HPLC Results on a Peptide COA