---
title: "Elemental impurities (ICH Q3D) and synthetic peptides | Sable Peptides"
description: "What elemental impurities are, how ICH Q3D classifies them, how ICP-MS and ICP-OES measure them, and where metals can enter peptide synthesis and purification. Research use only."
canonical: https://www.sablepeptides.co.uk/guides/elemental-impurities-ich-q3d-and-peptides
dateModified: 2026-10-16
publisher: Sable Peptides Limited (UK company 17488610)
note: Research use only. Not for human or veterinary use.
---

# Elemental impurities (ICH Q3D) and synthetic peptides

Elemental impurities are trace metals and metalloids that can enter a material from catalysts, reagents, equipment or containers. ICH Q3D sets a risk-based framework for them in medicines. Research peptides are not medicines, but the framework is a useful way to think about metal contamination in laboratory reagents.

## Definitions

-   Elemental impurity: a trace element not intentionally added, or added as a catalyst and not fully removed.
-   Class 1: elements of high toxicity (arsenic, cadmium, mercury, lead) assessed for every product.
-   Class 2 and 3: other elements assessed according to likelihood of presence and route.
-   ICP-MS / ICP-OES: inductively coupled plasma with mass spectrometry or optical emission detection, the usual measurement techniques.

Source: [ICH Q3D(R2) Guideline for Elemental Impurities (2022)](https://database.ich.org/sites/default/files/Q3D-R2_Guideline_Step4_2022_0308.pdf)

## Risk assessment rather than blanket testing

Q3D asks manufacturers to identify potential sources (reagents, water, equipment, container closure) and test where a risk is identified. Published case studies show the 'component approach', using supplier and excipient data, confirmed by finished-product testing; shared excipient databases support the same assessment.

Source: [ICH Q3D elemental impurities: component approach confirmed by finished-product testing, Ann Pharm Fr 2025 (PubMed 40378920)](https://pubmed.ncbi.nlm.nih.gov/40378920/); [ICH Q3D risk assessment using an excipients database, J Pharm Sci 2022 (PubMed 34673095)](https://pubmed.ncbi.nlm.nih.gov/34673095/)

## Measurement

ICP-MS offers lower detection limits; ICP-OES is robust for higher concentrations. A comparative study of both in a liquid pharmaceutical shows how the choice depends on the limits that need to be reached.

Source: [Elemental impurities by ICP-OES and ICP-MS: comparative analysis, Drug Dev Ind Pharm 2020 (PubMed 31999195)](https://pubmed.ncbi.nlm.nih.gov/31999195/)

## Where metals can enter peptide work

-   Palladium or other catalysts where protecting-group chemistry uses them.
-   Metal ions from buffers, salts and water used in purification.
-   Stainless-steel equipment and chromatography hardware.
-   Deliberate metal complexes, such as copper peptides, where the metal is part of the compound and is not an impurity.

## What to ask a supplier

Most research-grade CoAs report identity and purity only. If trace metals matter for your assay, for example metalloprotein or redox studies, ask whether an elemental screen is available or test in-house by ICP-MS. 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

### Which elements are ICH Q3D Class 1?

Arsenic, cadmium, mercury and lead.

### How are elemental impurities measured?

Usually by ICP-MS or ICP-OES after sample digestion.

### Do research peptide CoAs include metals testing?

Usually not; identity and HPLC purity are the standard release tests.

## Related

-   [Method validation terms (ICH Q2)](/guides/analytical-method-validation-terms-on-a-coa)
-   [Impurity types in peptide manufacturing](/learn/manufacturing/impurity-types)
-   [How to read a CoA](/guides/how-to-read-a-coa)
-   [Quality at Sable](/quality)
-   [Residual solvents (ICH Q3C)](/guides/residual-solvents-ich-q3c-and-peptides)

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)

-   Guideline: ICH Q3D(R2) (2022)
-   Class 1: As, Cd, Hg, Pb
-   Techniques: ICP-MS, ICP-OES
-   References: ICH Q3D PDF; PubMed 40378920, 34673095, 31999195
-   Updated 2026-10-16