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General information about a standard and a regulator’s published recommendations, not medical advice and not a substitute for the standard itself or for advice from a qualified test laboratory.
Short answer
ISO 10993-12 (also written ISO 10993 12) is the part of the ISO 10993 series that covers how a medical device or material is prepared for biological testing, including how test extracts are made. FDA’s guidance on using ISO 10993-1, issued September 8, 2023, points to it for extract amounts, solvents, extraction conditions and extract storage. It does not decide which biological endpoints a device needs; that is the job of ISO 10993-1.
Definition and scope
ISO 10993 is a multi-part series on the biological evaluation of medical devices. Part 1 sets out evaluation and testing within a risk management process, and FDA’s guidance on it is covered on FDA guidance on biocompatibility and ISO 10993. Part 12 deals with the step before many of those tests run: turning a device into something a test system can be exposed to, usually an extract. FDA’s text cites the 2021 edition, ISO 10993-12:2021.
The preparation choices FDA asks to be stated and justified are the surface-area-to-extract-volume ratio, the solvent, the temperature and time, and how the extract is handled and stored; they are set out below.
How extracts are prepared, according to FDA
FDA’s section on preparation for extract testing sets out a sequence that a test plan or report should follow. The points below restate that guidance.
1. Choose the amount of test article
- Determine the amount of test article as outlined in ISO 10993-12 or another FDA-recognized standard (FDA names ASTM F619, a standard practice for extraction of materials used in medical devices), using surface area to extract volume ratios.
- Mass to extract volume ratios are for cases where surface area cannot be calculated, or where using mass would produce a larger surface area to extract volume ratio than ISO 10993-12 recommends. An alternate ratio needs appropriate justification.
- For fluid path devices, the fluid path can be filled to capacity. If the ISO 10993-12 recommended ratio cannot be achieved, the fluid-contacting surface area and extraction volume should be noted in the test report. This applies to static and dynamic extractions.
2. Choose the solvents
FDA recommends using both polar and nonpolar solvents, such as those described in ISO 10993-12. Other solvents may be used where appropriate. FDA’s example is a mixed-polarity solvent such as cell culture medium with 5 to 10 percent serum for cytotoxicity testing.
3. Choose the extraction conditions
FDA states that traditional extraction methods, such as those in ISO 10993-12:2021, are acceptable for many biocompatibility tests. It lists these examples:
| Temperature | Duration |
|---|---|
| 37 °C | 72 hours |
| 50 °C | 72 hours |
| 70 °C | 24 hours |
| 121 °C | 1 hour |
FDA adds two cautions. For devices with prolonged or long-term contact, 37 °C may not be sufficient, while higher temperatures can generate chemicals that are not seen in clinical use. For heat-sensitive materials such as drugs, biomolecules or tissue-derived materials, FDA says extraction at 37 °C per ISO 10993-12 is recommended. In all cases, a justification for the selected extraction conditions should be provided.
4. Handle the extract
FDA asks that the extract’s condition (for example colour or particles) and any solvent change before and after extraction be reported, and that extracts be used without extra processing such as filtration, centrifugation or pH adjustment unless that is justified. Extracts should be used within the time frame given in ISO 10993-12 or an equivalent standard, with storage conditions described. FDA quotes ISO 10993-12:2021 that the “stability and homogeneity of the extract under the storage conditions shall be verified”.
Checklist: what a test report should document
This checklist is an editorial summary of the FDA recommendations above, useful when reading a test report or writing a test plan. Each line traces to the FDA guidance section on preparation for extract testing.
| Item | What FDA says should be documented or justified |
|---|---|
| Ratio and its basis | Surface area to extract volume per ISO 10993-12 or another recognized standard; justification if mass is used or a different ratio |
| Fluid path devices | Fluid-contacting surface area and extraction volume, if the recommended ratio could not be reached |
| Solvents | Polar and nonpolar solvents; justification for any other solvent |
| Conditions | Temperature and time, with a justification in all cases |
| Extract appearance | Colour, particles, and any solvent change before and after extraction |
| Processing | Whether the extract was used as is; justification for filtration, centrifugation or pH adjustment |
| Storage | Storage time and conditions, and why they do not affect results (stability and homogeneity verified) |
Where it matters for labs, clinics and supply decisions
FDA gives device-specific examples. A filled hemodialyzer has a much higher surface area to extract volume ratio than ISO 10993-12 recommends, and FDA says that if its non-membrane components are tested separately, ISO 10993-12 applies to them. For submicron or nano components, FDA notes that limitations may apply when using chemical-leachate-based ISO 10993-12 test conditions.
For anyone reading a biocompatibility summary from a manufacturer or test lab, the practical use of this section is to check that the preparation facts above are stated, not to judge a product. Related background: ISO 13485 quality management for medical devices, sterilization technology, the ethylene oxide sterilization process and extractables and leachables in single-use systems.
Common misunderstandings
Is ISO 10993-12 the same as ISO 10993-1?
No. ISO 10993-1 covers evaluation and testing within a risk management process; ISO 10993-12 covers preparing samples and extracts for the tests. FDA’s guidance on ISO 10993-1 refers to ISO 10993-12 for the preparation step.
Does it define exhaustive chemical extraction?
FDA refers exhaustive extraction for chemical analysis to ISO 10993-18, not ISO 10993-12.
Is one temperature always acceptable?
No. FDA lists several accepted condition pairs and asks for a justification for the one chosen, noting that 37 °C may be insufficient for prolonged or long-term contact devices and preferred for heat-sensitive materials.
FAQ
Is ISO 10993 12 the same standard as ISO 10993-12?
Yes. The two spellings refer to the same part of the series, ISO 10993-12, on sample preparation for biological testing.
What does ISO 10993-12 cover?
Preparation of test articles and extracts for biological testing, including amounts, solvents, extraction conditions and extract storage, as cited in FDA’s September 8, 2023 guidance.
What edition does FDA cite?
FDA’s 2023 guidance cites ISO 10993-12:2021 for its example extraction conditions and storage statement.
Sources
- U.S. Food and Drug Administration, Use of International Standard ISO 10993-1, “Biological evaluation of medical devices – Part 1: Evaluation and testing within a risk management process”, guidance issued September 8, 2023, section on preparation for extract testing. Checked 2026-11-01.
