ISO 10993-15:2019 Biological evaluation of medical devices – Part 15: Identification and quantification of degradation prod ucts from metals and alloys

ISO 10993-15:2019 Biological evaluation of medical devices – Part 15: Identification and quantification of degradation prod ucts from metals and alloys.
5 Reagent and sample preparation
5.1 Sample documentation
The general composition of the material(s) under test shall be documented.
5.2 Test solution (electrolyte)
The test solution (electrolyte) to be used shall be appropriate for the intended use of the medical device. All chemicals shall be of analytical grade and dissolved in water of grade 2 in accordance with Iso 3696.
The first choice for the electrolyte shall be an aqueous solution of 0,9 % sodium chloride.
Dependent on the composition and corrosion mechanism of the metal or alloy being tested, other electrolytes may be used, such as artificial saliva or artificial plasma. Examples of electrolyte compositions are given in Annex A. but other more material and physiologically relevant electrolyte solutions and test conditions may be utilized. Possible effect of implant—related protein interactions should be taken into account.
NOTE Formulations for artificial sweat, gastrointestinal fluids, and lung fluids have been used (see Bibliography).
In the test report, the choice of electrolyte shall be justified. If other than an aqueous solution of 0,9 % sodium chloride is used, the pH of the electrolyte shall be specified.
5.3 Preparation of test samples
5.3.1 Test samples
The sensitivity of chemical degradation testing is related to variation in material composition, to material processing, and to surface-finishing procedures. The sampling procedure, sample shape, and surface preparation are critical. In addition, confined spaces within or around the test article can result in crevice corrosion and defects in coatings can cause pit corrosion, both of which shall be taken into consideration. The samples shall be representative of the final devices.
5.3.2 Sampling
For each chemical test, multiple test samples shall be prepared as specified in ISO 10993-12. If substantial differences in the test results are found, the reasons for the difference shall be determined, and more samples shall be tested. The number of samples shall be justified.
If the metallic sample has anisotropic properties due to manufacturing conditions, tests involving single-surface exposure should include samples cut parallel to both the transverse and longitudinal manufacturing directions.
5.3.3 Sample shape
Standard samples (e.g. circular- or rectangular-section bars, flat coupons, one single free surface) may be used for degradation testing if they are prepared in a manner comparable to the final medical device. Samples of actual device components maybe of any shape and condition; however, the testing shall be carried out under well-controlled conditions which shall be reported.
The surface area of the sample exposed to the electrolyte shall be determined to ±10 % of the total geometrical area to assure an accurate and repeatable determination of the degradation rates.
If representative samples are used, consideration shall be made regarding whether the differences between the representative sample and the final medical device or component could affect the results of the test.ISO 10993-15 pdf download.