5.1 These extraction procedures are the initial part of several test procedures used in the biocompatibility screening of plastics used in medical devices.

5.2 The limitations of the results obtained from this practice should be recognized. The choice of extraction vehicle, duration of immersion, and temperature of the test is necessarily arbitrary. The specification of these conditions provides a basis for standardization and serves as a guide to investigators wishing to compare the relative resistance of various plastics to extraction vehicles.

5.3 Correlation of test results with the actual performance or serviceability of materials is necessarily dependent upon the similarity between the testing and end-use conditions (see 12.1.2 and Note 4).

5.4 Caution should be exercised in the understanding and intent of this practice as follows:

5.4.1 No allowance or distinction is made for variables such as end-use application and duration of use. Decisions on selection of tests to be done should be made based on Practice F748.

5.4.2 This practice was originally designed for use with nonporous, solid materials. Its application for other materials, such as those that are porous, or absorptive, or resorptive, should be considered with caution. Consideration should be given to altering the specified material to liquid ratio to allow additional liquid to fully hydrate the material and additional liquid or other methods to fully submerge the test article. Additional procedures that fully remove the extract liquid from the test article, such as pressure or physically squeezing the material, should also be considered as appropriate. Although no definitions are given in this practice for the following terms, such items as extraction vehicle surface tension at the specified extraction condition and plastic specimen physical structure should be taken into account.

5.5 Test Methods D543, D570, and D1239 may be useful in providing supplemental information.