> 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/laboratory-terms/analytical-method.md).

# Analytical Method

## Definition

An analytical method is a documented procedure for performing a chemical or physical analysis, specifying the equipment, reagents, conditions, and calculations required to obtain a result.

## Overview

Analytical methods are the foundation of quality testing. Each test on a COA (HPLC purity, MS identity, assay) is performed according to a validated analytical method that ensures consistent, reliable results.

## Technical Explanation

**Common Analytical Methods for Peptides:**

| Method              | Purpose                       | Key Parameters                          |
| ------------------- | ----------------------------- | --------------------------------------- |
| RP-HPLC             | Purity determination          | Column, gradient, wavelength, flow rate |
| LC-MS               | Identity + purity             | HPLC conditions + MS parameters         |
| Mass Spectrometry   | Molecular weight confirmation | Ionization mode, mass range             |
| Amino Acid Analysis | Composition verification      | Hydrolysis, derivatization, detection   |
| Karl Fischer        | Water content                 | Titration parameters                    |
| LAL Test            | Endotoxin detection           | Sensitivity, incubation conditions      |

**Method Validation Parameters (ICH Q2):**

* Accuracy (recovery)
* Precision (repeatability, intermediate precision)
* Specificity (ability to measure the analyte without interference)
* Detection Limit (LOD)
* Quantitation Limit (LOQ)
* Linearity (response vs. concentration)
* Range
* Robustness

## Importance in Peptide Documentation

The analytical method used for each test is listed on the COA. Reproducibility of results depends on using consistent methods. Method changes require re-validation and may affect specification limits.

## Related Terms

* [HPLC](/docs/glossary/analytical-terms/hplc.md)
* [Mass Spectrometry](/docs/glossary/analytical-terms/mass-spectrometry.md)
* [Reference Standard](/docs/glossary/laboratory-terms/reference-standard.md)

## Frequently Asked Questions

**Q: Are all peptide purity methods the same?** A: No. Different peptides require different HPLC conditions (column, gradient, wavelength) optimized for their specific properties. Method transfer between labs requires verification.

**Q: What is "method validation"?** A: Validation demonstrates that an analytical method is suitable for its intended purpose. Validated methods provide confidence that test results are accurate and reliable.


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