> 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/hplc.md).

# High Performance Liquid Chromatography (HPLC)

## Definition

High Performance Liquid Chromatography (HPLC) is an analytical technique used to separate, identify, and quantify components in a mixture. In peptide quality control, HPLC is the primary method for purity determination.

## Overview

HPLC is the gold standard analytical method for assessing peptide purity. It separates peptide products from impurities (truncated sequences, deletion peptides, oxidation products, residual solvents) based on differences in their interactions with a stationary phase and a mobile phase.

## Technical Explanation

**How HPLC Works:** A sample is injected into a flowing liquid stream (mobile phase) that passes through a column packed with solid particles (stationary phase). Components interact differently with the stationary phase, causing them to elute (exit) at different times.

**Main Components:**

* Solvent reservoirs and pumps (deliver mobile phase at high pressure)
* Autosampler/intel (injects the sample)
* Column (contains stationary phase — typically C18 for peptide analysis)
* Detector (UV/PDA, ELSD, or MS — measures eluting compounds)
* Data system (processes signal into a chromatogram)

**RP-HPLC for Peptides:** Most peptide purity analysis uses Reversed Phase HPLC (RP-HPLC) with:

* C18 or C8 columns
* Water/acetonitrile mobile phase with TFA (0.05–0.1%)
* UV detection at 214 nm (peptide bond absorbance) or 280 nm (aromatic residues)
* Gradient elution (increasing organic solvent over time)

## Importance in Peptide Documentation

HPLC purity is the most important specification on a Certificate of Analysis (COA). HPLC analysis detects and quantifies impurities, confirming that the product meets the stated purity specification (e.g., ≥98%). The HPLC chromatogram itself is an essential quality document.

## Related Terms

* [Purity](/docs/glossary/analytical-terms/purity.md)
* [Chromatogram](/docs/glossary/analytical-terms/chromatogram.md)
* [Retention Time](/docs/glossary/analytical-terms/retention-time.md)
* [Peak Area](/docs/glossary/analytical-terms/peak-area.md)
* [LC-MS](/docs/glossary/analytical-terms/lc-ms.md)
* [Impurity](/docs/glossary/analytical-terms/impurity.md)
* [COA](/docs/glossary/quality-control/coa.md)

## Frequently Asked Questions

**Q: What does "HPLC purity ≥98%" mean?** A: It means that, by HPLC area normalization, the main peptide peak represents at least 98% of the total detected peak area. Impurities account for ≤2%.

**Q: Why is UV detection at 214 nm preferred for peptides?** A: The peptide bond absorbs strongly at \~214 nm, making this wavelength suitable for detecting all peptides regardless of amino acid composition. Detection at 280 nm is specific for aromatic residues (tryptophan, tyrosine, phenylalanine).


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