If your silicone part touches a drug product, IV fluid or the human body, regulators will ask about extractables and leachables (E&L). This article explains what the terms mean, which standards apply, and what documentation you should ask your silicone supplier for — in plain engineering language.
Extractables vs. Leachables: The Key Distinction
The two terms are often confused, but they describe different stages of the same investigation:
| Term | What it measures | When it is run |
|---|---|---|
| Extractables | Chemical substances pulled out of the material under aggressive lab conditions (strong solvents, heat, extended time) | Early, as a "worst-case" screening of what the material could release |
| Leachables | Substances that actually migrate into the real drug product or fluid under normal-use conditions | Later, on the finished device or drug, as part of stability studies |
Think of extractables as the full list of "what might come out," and leachables as the smaller, real-world list of "what actually does." A material with a broad extractables profile can still have an acceptably small leachables profile once real contact conditions are applied.
The Standards That Govern E&L
- ISO 10993-18 — the core standard for chemical characterization of medical-device materials. It sets the framework for designing an extractables study: solvent selection, extraction conditions and analytical methods.
- USP <1663> and <1664> — pharmaceutical-focused chapters on assessing extractables and leachables for packaging and delivery systems (US Pharmacopeia).
- ISO 10993-1 — the parent standard that drives when chemical characterization is required as part of a biological-evaluation plan.
- ICH Q3C / Q3D — residual-solvent and elemental-impurity limits that feed into E&L risk assessment.
For silicone specifically, the relevant concerns are typically residual siloxanes (low-molecular-weight cyclic or linear oligomers such as D4, D5, D6), platinum-catalyst residues, peroxide by-products, and any compounding additives. Platinum-cured LSR generally produces a cleaner extractables profile than peroxide-cured solid silicone, which is one reason it is preferred for many drug-contact and long-term implantable-adjacent applications.
What a Solvent Panel Typically Includes
Because no single solvent mimics every fluid, extractables studies run a panel that brackets a range of polarities:
- Polar / aqueous — water, buffered saline, or an alcohol–water mix.
- Semi-polar — isopropanol, or ethanol/water mixtures.
- Non-polar — hexane or another hydrocarbon, used as a worst-case for lipophilic extraction.
The choice of solvents and extraction conditions (temperature, time, surface-area-to-volume ratio) is dictated by the intended clinical use — this is where a well-designed study avoids both false negatives and unnecessary over-testing.
Analytical Techniques Used
- GC-MS — identifies and quantifies volatile and semi-volatile organics, including cyclic siloxanes.
- LC-MS / HPLC — covers non-volatile and thermally labile compounds.
- ICP-MS / ICP-OES — measures elemental impurities and metal residues.
- FTIR and gravimetric NVR — non-volatile-residue screening and material fingerprinting.
See our silicone testing methods guide for a deeper look at ICP-OES and GC-MS specifically.
What to Request from Your Silicone Supplier
Before you commit, ask for documentation that shows the material has been characterized, not just "certified":
- A material extractables report with the solvent panel, conditions and detected compounds listed — not just a pass/fail summary.
- ISO 10993-18 chemical-characterization data, or a statement of readiness to support one.
- Biocompatibility test data to USP Class VI and/or the relevant ISO 10993 endpoints for your contact duration.
- The cure system used (platinum vs. peroxide) — this materially affects the extractables profile.
- Raw-material traceability to a named silicone feedstock (Elkem, Dow, DuPont or equivalent) so results are reproducible lot-to-lot.
How CYES SILICONE Supports E&L
We compound and mold medical-grade and platinum-cured LSR in-house, source silicone feedstock from suppliers including Elkem, Dow and DuPont, and test every incoming raw-material lot before production. For drug-contact and medical projects we support chemical-characterization programs by providing material identity, cure-system detail and traceable documentation to your ISO 10993-18 or USP <1663> study — so your regulatory file is built on a characterized material rather than an assumption. See our quality documents page for the full documentation set we can provide.