Standard Practice for Extraction of Medical Plastics
These extraction procedures are the initial part of several test procedures used in the biocompatibility screening of plastics used in medical devices.
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.
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).
Caution should be exercised in the understanding and intent of this practice as follows:
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 F 748.
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.
Test Methods D 543, D 570, and D 1239 may be useful in providing supplemental information.
1.1 This practice covers methods of extraction of medical plastics and may be applicable to other materials. This practice identifies a method for obtaining “extract liquid” for use in determining the biological response in preclinical testing. Further testing of the “extract liquid” is specified in other ASTM standards. The extract may undergo chemical analysis as part of the preclinical evaluation of the biological response, and the material after extraction may also be examined.
1.2 This practice may be used for, but is not limited to the following areas: partial evaluation of raw materials, auditing materials within the manufacturing process, and testing final products. This practice may also be used as a referee method for the measurement of extractables in plastics used in medical devices.
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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