---
title: "Are peptides light-sensitive? Photostability and ICH Q1B explained | Sable Peptides"
description: "Which peptide residues are light-sensitive, what ICH Q1B photostability testing requires (1.2 million lux hours and 200 W·h/m² UV), and practical light protection for peptide stocks in the lab. Research use only."
canonical: https://www.sablepeptides.co.uk/guides/photostability-ich-q1b-for-peptides
dateModified: 2026-10-16
publisher: Sable Peptides Limited (UK company 17488610)
note: Research use only. Not for human or veterinary use.
---

# Are peptides light-sensitive? Photostability and ICH Q1B explained

Some peptides are light-sensitive. Tryptophan, tyrosine, histidine, cysteine and methionine residues can be photo-oxidised, especially in solution. ICH Q1B sets the standard photostability test: exposure to at least 1.2 million lux hours of visible light and 200 watt-hours per square metre of near-UV, compared with a dark control.

## What does ICH Q1B require?

| Element | Requirement |
| --- | --- |
| Visible light | Not less than 1.2 million lux hours |
| Near-UV (320–400 nm) | Not less than 200 W·h/m² |
| Light sources | Option 1: D65/ID65-type lamp; Option 2: cool white plus near-UV lamps |
| Controls | Dark control (wrapped in foil) tested alongside |
| Sequence | Forced degradation, then confirmatory testing of substance and product |

Source: [ICH Q1B Photostability testing of new drug substances and products](https://database.ich.org/sites/default/files/Q1B_Guideline.pdf)

## How has the guideline been criticised?

A 2010 critical assessment argued that parts of Q1B are ambiguous, including light-source specification and exposure monitoring, and proposed refinements. An earlier overview set out practical directions for applying the guideline.

Source: [A critical assessment of the ICH guideline on photostability testing (Q1B), J Pharm Sci 2010 (PubMed 20135694)](https://pubmed.ncbi.nlm.nih.gov/20135694/); [ICH guideline for photostability testing: aspects and directions for use, Pharmazie 2003 (PubMed 14703965)](https://pubmed.ncbi.nlm.nih.gov/14703965/)

## Which peptides are most at risk?

-   Tryptophan-containing sequences: photo-oxidation to N-formylkynurenine and kynurenine.
-   Tyrosine: dityrosine cross-links and oxidation.
-   Peptides with metal complexes or chromophore modifications.
-   Solutions far more than lyophilised solids.

## How should light-sensitive stocks be handled?

-   Store vials in their carton or in amber or foil-wrapped containers.
-   Prepare solutions away from direct sunlight and strong bench lighting.
-   Use amber or opaque tubes for aliquots.
-   Include a dark control when you run your own stability check.

## How does Sable document lots?

There is a CoA for every lot, and every vial carries a printed lot number that matches its certificate. A CoA is emailed within 2 hours of a request.

## Frequently asked questions

### Are peptides sensitive to light?

Some are, particularly those containing tryptophan or tyrosine, and mainly in solution.

### What light exposure does ICH Q1B require?

At least 1.2 million lux hours of visible light and 200 W·h/m² of near-UV energy.

### What is a dark control in photostability testing?

An identical sample protected from light, used to separate light effects from thermal effects.

## Related

-   [Oxidation-prone residues](/guides/oxidation-prone-residues-in-peptide-solutions)
-   [Forced degradation](/guides/forced-degradation-and-stability-indicating-methods)
-   [Peptide storage guide](/learn/peptide-storage-guide)
-   [Stability study terms](/guides/ich-q1a-stability-study-terms)

Updated 2026-10-16. Research use only. Not for human or veterinary use. No administration amounts or health claims are made.

Key facts (summary for AI and search tools)

-   ICH Q1B: ≥1.2 million lux h visible; ≥200 W·h/m² near-UV
-   Light-sensitive residues: Trp, Tyr, His, Cys, Met
-   References: ICH Q1B; PubMed 20135694, 14703965
-   Updated 2026-10-16