> 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/lc-ms.md). # LC-MS ## Definition Liquid Chromatography Mass Spectrometry (LC-MS) is a hyphenated analytical technique that combines the separation power of HPLC with the detection and identification capability of mass spectrometry. ## Overview LC-MS is a powerful tool for peptide analysis that simultaneously provides both separation (like HPLC) and molecular weight identification (like MS). It is widely used for identity confirmation and detailed impurity characterization. ## Technical Explanation **How LC-MS Works:** 1. HPLC separates sample components by retention time 2. As each component elutes, it enters the mass spectrometer 3. The MS ionizes the compound and measures mass-to-charge ratio (m/z) 4. Data is presented as a total ion chromatogram (TIC) plus mass spectra for each peak **Advantages Over HPLC Alone:** * Simultaneous separation and identification * Each peak is identified by molecular weight * Can distinguish co-eluting compounds with different masses * Provides structural information through fragmentation (MS/MS) * Higher sensitivity for impurity detection ## Importance in Peptide Documentation LC-MS provides the most comprehensive quality assessment — combining purity (HPLC separation) with identity (mass confirmation). RPL Peptide uses LC-MS for identity verification and impurity characterization in its quality control workflows. ## Related Terms * [HPLC](/docs/glossary/analytical-terms/hplc.md) * [Mass Spectrometry](/docs/glossary/analytical-terms/mass-spectrometry.md) * [Identity](/docs/glossary/analytical-terms/identity.md) * [Purity](/docs/glossary/analytical-terms/purity.md) ## Frequently Asked Questions **Q: Is LC-MS better than HPLC for purity analysis?** A: LC-MS provides additional identity information for each peak, making it superior for impurity identification. However, HPLC with UV detection remains the standard for quantitative purity determination due to better UV response linearity. **Q: Does every COA include LC-MS data?** A: Most comprehensive COAs include LC-MS data for identity confirmation. Purity is typically reported from HPLC-UV analysis. RPL Peptide COAs include both HPLC purity data and MS identity confirmation. --- # 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/lc-ms.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.