Heavy metals testing: lead, arsenic, cadmium, mercury.
Heavy metals testing measures toxic elemental impurities — lead, arsenic, cadmium, and mercury above all — that can enter peptides through reagents, catalysts, and equipment. The standard method is ICP-MS (inductively coupled plasma mass spectrometry), and limits follow the USP <232>/<233> elemental impurities framework. Results should appear on the COA for serious research material.
Why heavy metals matter in peptide production
Peptide synthesis uses solvents, reagents, and sometimes metal-containing catalysts, and materials contact glassware and equipment throughout processing. Elemental impurities — lead, arsenic, cadmium, mercury, and others — can ride along. They carry toxic risks entirely unrelated to the peptide itself, and unlike microbial contamination they don't announce themselves.
The method: ICP-MS
Inductively coupled plasma mass spectrometry is the standard quantification technique:
- The sample is digested (destroyed) into a solution.
- A plasma torch ionizes everything in it.
- The mass spectrometer counts ions of each element by mass.
The result is a concentration per element, at parts-per-billion sensitivity.
The limits framework
Pharmaceutical practice follows USP <232> (which elemental impurities matter and their permitted daily exposures) and USP <233> (how to measure them). Research peptide COAs that report elemental analysis typically reference these frameworks or their ICH Q3D equivalent.
What to look for on a COA
- Named elements with numeric results (e.g., "Pb: <0.5 ppm"), not a bare "heavy metals: pass."
- The method named (ICP-MS or equivalent).
- Batch-specific results — see how to read a peptide COA.
Heavy metals testing rounds out the safety picture alongside endotoxin and sterility; together with purity and identity, they make up the core of a complete testing panel.
Questions. answered.
Why test peptides for heavy metals?
Synthesis reagents, catalysts, and equipment can introduce toxic elements like lead and mercury. They are invisible to purity methods like HPLC, so elemental analysis (ICP-MS) is required to detect them.
What are USP <232> and <233>?
USP chapters defining which elemental impurities matter and their exposure limits (<232>) and the analytical procedures for measuring them (<233>).