How to Read Certificates of Analysis (COAs): A Complete Guide for Researchers

Understanding the Documentation Behind Peptide Quality Assurance

When you purchase research-grade peptides, the Certificate of Analysis (COA) is your assurance of quality. But what do all those numbers, graphs, and technical terms actually mean? This guide walks you through each section of a PekCura Labs COA so you can quickly verify purity, quantity, sterility, and safety for your research.

Every peptide batch we ship includes a COA from an ISO 17025:2017-accredited third-party laboratory. Each document provides independent verification of what is in your vial. Understanding how to read these reports empowers you to make informed decisions about the materials you use in your laboratory.

Why COAs Matter in Peptide Research

Certificates of Analysis serve three critical functions:

Transparency. You receive documented proof of exactly what you ordered, tested by independent laboratories with no commercial interest in the results.

Traceability. Each COA links to a specific batch through unique lot numbers, allowing you to track materials from manufacturing through analysis to your laboratory bench.

Regulatory Compliance. For research institutions and organizations subject to oversight, COAs provide the documentation needed to demonstrate material quality and safety.

At PekCura Labs, we make COAs accessible via QR codes on every vial. Scan the code with your phone and you will immediately see the complete analytical results for the peptide.

Report Header: Identifying Your Batch

The top section of every COA contains essential identifying information:

Compound Name: The peptide tested. In our example, you will see PCL-Semaglutide clearly listed.

Quantity Received: The amount submitted for testing. This example shows 10 mg, which represents the labeled amount.

Lot Number: A unique identifier that allows complete traceability. For this batch, the lot number is 81225. You can reference this number in your research documentation and lab notebooks.

Laboratory ID: The testing laboratory’s internal tracking number for their records.

Date Reported: When the analysis was completed. Our example shows 9/12/2025.

This header information allows you to confirm you are reviewing results for the specific peptide batch you received. Always verify the lot number on your vial matches the lot number on the COA.

Chromatographic Purity: The Primary Quality Metric

Purity is the most critical specification for research peptides.

Method: HPLC-UV/VIS (High Performance Liquid Chromatography with ultraviolet detection). This is the gold standard analytical technique for peptide purity assessment.

Result: In this example, 99.56% +/- 0.18%.

This percentage tells you what proportion of your sample is the target peptide versus impurities such as truncated sequences, deletion peptides, or manufacturing by-products. The +/- value represents the analytical precision of the method itself.

For most research applications, purity above 95% is acceptable. PekCura Labs peptides consistently exceed 98% purity, with many batches reaching 99% or higher. This level of purity minimizes confounding variables in your experiments and ensures reproducible results.

Quantity Measurement: Confirming What You Ordered

Method: HPLC-UV/VIS against a reference standard.

Result: 12.13 mg in this example.

While the vial label indicated 10 mg, the actual measured amount was 12.13 mg. This is common and reflects conservative labeling practices. Analytical tolerances and humidity absorption during weighing can cause slight variations. What matters is that you receive at least the labeled amount of peptide at the specified purity.

The quantity measurement uses the same HPLC system as the purity analysis, ensuring consistency between the two most important specifications.

Sterility Testing: Confirming Absence of Contamination

Method: USP <71> (United States Pharmacopeia Sterility Tests).

Result: PASS – No Growth.

This test confirms no microbial contamination was detected in the sample. Testing follows standardized protocols where the peptide is incubated in growth media under conditions that would support bacterial or fungal growth if present.

For peptides used in cell culture or other sensitive biological assays, sterility is essential. Contamination can compromise experimental results and waste valuable research time and resources.

Endotoxin Testing: Bacterial Byproduct Analysis

Method: LAL (Limulus Amebocyte Lysate assay).

Result: PASS – 2.51 EU/mg (Endotoxin Units per milligram).

Endotoxins are lipopolysaccharides from gram-negative bacterial cell walls. Even when bacteria are absent, endotoxins can persist and trigger inflammatory responses in biological systems. The LAL assay detects endotoxins with high sensitivity.

Regulatory guidelines typically specify thresholds of less than 5 EU/kg or less than 350 EU total for a 70 kg adult. At 2.51 EU/mg, this sample passes comfortably within acceptable limits for research use.

Reading the Chromatogram: Visual Confirmation of Purity

Every COA includes a chromatogram, which is the graphical output from the HPLC analysis.

X-axis: Retention time in minutes. This represents how long compounds take to pass through the chromatography column.

Y-axis: Detector response in mAU (milli-absorbance units). This represents the concentration of material detected.

Main Peak: The tall, dominant peak represents your target peptide. In a high-purity sample, this peak will be sharp and well-defined.

Minor Peaks: Smaller peaks indicate impurities. The relative size of these peaks compared to the main peak determines the overall purity percentage.

The chromatogram provides visual confirmation of what the numerical purity data tells you. A clean chromatogram with one dominant peak and minimal impurity peaks gives you confidence in the quality of your peptide.

Accreditation and Approval: Independent Validation

At the bottom of each COA you will find:

ISO 17025:2017 Accreditation Seal. This confirms the testing laboratory meets international standards for technical competence, quality management, and reliability. ISO 17025 accreditation is the highest standard for analytical laboratories.

Laboratory Signatures. The lab director and operations manager sign each report, providing official approval and accountability for the results.

This independent verification means you can trust the data. The laboratory has no financial interest in passing or failing samples. They simply report what their validated analytical methods detect.

Using COAs in Your Research Documentation

When you receive peptides from PekCura Labs, incorporate the COA into your research records:

• Reference the lot number in your lab notebook when documenting experiments
• File the COA with your materials documentation for regulatory or institutional compliance
• Compare purity and quantity specifications when troubleshooting experimental variability
• Include COA data in methods sections of publications when peptide quality is relevant to your findings

Proper documentation practices protect the integrity of your research and provide traceability if questions arise later.

Key Takeaways: What to Look For in Every COA

A quality Certificate of Analysis should provide:

Purity above 95%, with PekCura Labs consistently exceeding 99%. This ensures your peptide contains minimal impurities that could affect experimental results.

Quantity verification confirming you received at least the labeled amount. Slight overages are common and acceptable.

Sterility confirmation showing no microbial contamination. This is critical for cell culture and biological assay applications.

Endotoxin levels well below regulatory thresholds. Low endotoxin content protects against inflammatory responses in biological systems.

Clear chromatographic data with a dominant main peak and minimal impurity peaks. Visual inspection of the chromatogram builds confidence in numerical purity data.

Third-party accreditation from ISO 17025:2017 certified laboratories. Independent testing eliminates conflicts of interest and ensures objective results.

Transparency Through Third-Party Testing

At PekCura Labs, every peptide batch undergoes rigorous third-party analysis before reaching your laboratory. We do not test our own products because we believe independent verification provides the highest level of assurance.

Our COAs reflect our commitment to transparency and scientific rigor. When you scan the QR code on your vial, you access the same data we review internally. No hidden information, no selective reporting, just complete analytical results from accredited laboratories.

This approach ensures that what you order is what you receive, documented with data you can trust.