> For the complete documentation index, see [llms.txt](https://docs.rplpeptides.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rplpeptides.com/docs/guides/peptide-coa-interpretation-guide.md).

# Peptide COA Interpretation Guide

## 1. Understanding the COA Layout

A typical RPL Peptide Certificate of Analysis contains the following sections:

| Section       | Information Provided                                                       |
| ------------- | -------------------------------------------------------------------------- |
| Header        | Product name, batch/lot number, manufacturing date, expiry date            |
| Physical Data | Appearance, color, form (lyophilized powder/cake)                          |
| Purity Data   | HPLC purity at 214 nm and 254 nm                                           |
| Identity Data | Molecular weight confirmation (LC-MS), amino acid analysis (if applicable) |
| Composition   | Peptide content, counterion content (TFA⁻), water content (KF)             |
| Bioassay      | Endotoxin (LAL), bioburden (if applicable)                                 |
| Storage       | Recommended storage conditions                                             |
| Signatures    | QC manager authorization                                                   |

## 2. Interpreting HPLC Purity

* **214 nm purity**: The primary purity indicator. Values ≥98% indicate high purity.
* **254 nm purity**: Supplementary. Lower values at 254 nm suggest few aromatic residues.
* **Single main peak**: Target peptide. Should be clean and symmetrical.
* **Shoulder peaks**: May indicate closely eluting impurities — check resolution.
* **Multiple peaks**: Investigate for sequence heterogeneity or degradation.

## 3. Understanding Peptide Content

Peptide content (%) = (actual peptide mass / total powder mass) × 100%

A typical peptide content of 70–90% accounts for:

* Residual TFA counterions (5–15%)
* Bound water (2–5%)
* Other non-peptide components

**Important**: Always use the peptide content (%) to calculate the actual peptide amount for accurate dosing.

## 4. Common Issues and What They Indicate

| Observation                 | Possible Diagnosis            | Action                                 |
| --------------------------- | ----------------------------- | -------------------------------------- |
| Low 214 nm purity (< 95%)   | Significant impurity content  | Request batch-specific chromatogram    |
| High TFA content (> 15%)    | Excess counterion bound       | Request TFA-to-acetate exchange        |
| High water content (> 6%)   | Moisture ingress              | Verify vial integrity; use fresh batch |
| Mass deviation > 1 Da       | Identity concern              | Request LC-MS re-analysis              |
| Absence of expected MS peak | Degradation or wrong compound | Contact QC immediately                 |

## 5. Batch-to-Batch Comparison

Key parameters to track across batches:

1. HPLC purity at 214 nm (should be consistent within ±0.5%)
2. Impurity profile (same impurities, comparable relative levels)
3. Peptide content (consistent within ±3%)
4. LC-MS confirmed molecular weight (should match theoretical within ±0.5 Da)
5. Appearance (consistent white to off-white lyophilized cake)

***

*For COA interpretation assistance: <quality@rplpeptides.com>*


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