> 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/glossary/analytical-terms/chromatogram.md). # Chromatogram ## Definition A chromatogram is a graphical representation of the detector signal over time during an HPLC analysis. It shows the separation of sample components as peaks plotted against retention time. ## Overview The chromatogram (often called the "HPLC trace") is the primary visual output of an HPLC analysis. It provides a fingerprint of the sample's purity profile — a clean chromatogram with a single major peak indicates high purity, while multiple additional peaks indicate the presence of impurities. ## Technical Explanation **Reading a Chromatogram:** * X-axis: Retention time (minutes) * Y-axis: Detector response (absorbance units at UV wavelength) * Each peak represents a separated compound * Peak area correlates with quantity (proportional detection) * Peak shape indicates column performance and compound behavior **Key Chromatogram Features:** * Main peak: The target peptide * Impurity peaks: Additional compounds (identified by RRT) * Baseline: The detector signal between peaks (should be stable) * Tailing factor: Measure of peak symmetry (should be ≤2.0) * Resolution: Separation between adjacent peaks (should be ≥1.5) ## Importance in Peptide Documentation The HPLC chromatogram is included with each Certificate of Analysis as visual evidence of product quality. It allows researchers to independently assess the purity profile, not just rely on numerical purity values. ## Related Terms * [HPLC](/docs/glossary/analytical-terms/hplc.md) * [Retention Time](/docs/glossary/analytical-terms/retention-time.md) * [Peak Area](/docs/glossary/analytical-terms/peak-area.md) * [Purity](/docs/glossary/analytical-terms/purity.md) * [COA](/docs/glossary/quality-control/coa.md) ## Frequently Asked Questions **Q: How do I assess purity from a chromatogram?** A: Look for a single dominant peak. Any additional peaks (shoulders, small bumps, baseline separations) indicate impurities. Compare with reference chromatograms from trusted sources. **Q: What indicates a good quality HPLC analysis?** A: Good baseline stability, sharp symmetrical main peak, baseline separation from impurities (>1.5 resolution), and consistent retention time with established specifications. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.rplpeptides.com/docs/glossary/analytical-terms/chromatogram.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.