> 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/mass-spectrometry.md). # Mass Spectrometry ## Definition Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio (m/z) of ions to determine the molecular weight and structural information of compounds. It is the primary method for peptide identity confirmation. ## Overview Mass spectrometry is the gold standard for peptide identity verification. By providing an accurate molecular weight measurement, MS confirms that the synthesized peptide matches the theoretical mass calculated from its amino acid sequence. ## Technical Explanation **Principle:** 1. The sample is ionized (typically by ESI — Electrospray Ionization) 2. Ions are separated by their mass-to-charge ratio (m/z) 3. The detector records the abundance of each ion 4. The resulting mass spectrum shows m/z values vs. intensity **Ionization Methods for Peptides:** * **ESI:** Produces multiply charged ions (common for peptides and proteins) * **MALDI:** Produces singly charged ions (good for purity assessment) **Mass Analyzers:** * Quadrupole: Unit resolution, widely used * TOF: High resolution, accurate mass * Ion Trap: MS/MS capability **Data Interpretation:** The mass spectrum shows a series of multiply charged ions. Deconvolution software calculates the neutral molecular weight from the m/z series. ## Importance in Peptide Documentation Mass spectrometry data is an essential component of the Certificate of Analysis. It provides: * Molecular weight confirmation (identity) * Detection of sequence errors, deletions, or modifications * Evidence of correct counter-ion inclusion * Impurity identification (when combined with HPLC = LC-MS) ## Related Terms * [LC-MS](/docs/glossary/analytical-terms/lc-ms.md) * [Identity](/docs/glossary/analytical-terms/identity.md) * [Molecular Weight](/docs/glossary/chemical-terms/molecular-weight.md) * [Purity](/docs/glossary/analytical-terms/purity.md) ## Frequently Asked Questions **Q: What mass accuracy is needed for peptide identity confirmation?** A: For most peptides (MW 500–5000 Da), a mass accuracy within ±0.5 Da is sufficient for identity confirmation. High-resolution MS (±0.001 Da) provides even stronger confirmation. **Q: Can MS detect modifications?** A: Yes. Modifications (acetylation, amidation, oxidation) change the molecular weight by specific amounts. MS can detect these changes and identify the modification type from the mass shift. --- # 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/mass-spectrometry.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.