Contamination control in biomedical devices impacts soils regardless of status of viability.1-3 There is an ASTM working group and associated standard under development for overall assessment of extractable residue. The test method is geared toward metallic components to be used in implantable biomedical devices. We have been following the development of this standard4 and periodically provide progress reports. Development of the standard is of interest to biomedical device manufacturers and to the FDA. In addition, the emergence of this standard has potential profound, positive implications for all who are concerned with critical applications, where contamination control is a must.

The standard will be applicable to implantable metallic components with a range of soils, materials of construction, and product configuration. The standard under development would detect extractable contaminants using general gravimetric methods. Given the diversity of materials and soils, proposals for extraction methods include ultrasonics and refluxing with either water or any of an array of organic solvents.

The goal of the working group is to develop a standard, not a guidance document. This is significant in that, once the standard is finalized, companies can refer to it as a fairly specific part of their process. At the same time, it is likely that details of the extraction process will have to be documented for the specific product of concern. For example, it appears that given the diversity of contaminants and of product configurations, it would be unrealistic to specify or even to recommend one or two extraction solvents. In addition, given the diversity of safety and environmental regulations as well as specific company policies which restrict or even ban particular solvents, specifying a universally-acceptable solvent is daunting, and probably unachievable. Sampling techniques is another important issue. The challenge is to specify sampling in such a manner that product diversity and variable lot size (including small production runs) are accounted for.

The intent of the current work is relatively narrow; for example, the draft standard is not intended to cover re-usable biomedical devices. However, the current approach would be general enough, that applicability could range beyond that of the medical device community. By analogy, at one time, military specifications had power far beyond the military world. There are estimates that mil-specs were used by some 50% of businesses.5 The medical device standard, once developed and tested, has the potential for similar, if not greater broad-scale applicability.

The draft standard is obviously a work in progress. Depending on the extent of comments received, it is conceivable that the standard could be in place in the Fall of 2004. At that point, round-robin testing would begin.

Therefore, along with developing the new standard, the working group is also considering details of a round-robin testing. This will be a challenge. Obviously, not all conceivable parameters can be tested, so representative soils, substrates, and configurations will have to be selected. Pinning down the details of the ultrasonic process will also be a challenge. While ultrasonics are often considered in a rather generic sense, such factors as frequency, amplitude, tank design, solvent, time, and temperature can profoundly impact extraction efficiency. In addition, ultrasonics metrics is still in a developmental stage.6-8 The round-robin testing is therefore expected to yield results and findings which will also be valuable to the overall manufacturing community.

We live in a world inundated by standards. An effective standard, in our opinion, should be achieved by consensus and should be pertinent, achievable, practical, and adaptable to a range of applications, and not arbitrarily restrictive. The ASTM working group is taking important steps in a very critical area. The working group will continue its activities. In addition, a relevant symposium is planned for May 2005. We will continue to keep you posted.

We would like to thank ASTM Working Group F04.15.17 Chair, Dr. Stephen Spiegelberg of the Cambridge Polymer Group, for his helpful comments.

References:

a-d {. Kanegsberg, E. Kanegsberg, “Contamination Control In and Out of The Cleanroom,” A2C2 Magazine, (April, May, June, 2003).

f B. Kanegsberg, E. Kanegsberg, TContamination Control In and Out of The Cleanroom,” A2C2 Magazine, (October, 2003).

g W.G. Kenyon, Global Centre Consulting, personal communication.

h-k Œ. Kanegsberg, E. Kanegsberg, “Contamination Control In and Out of The Cleanroom,” A2C2 Magazine, (December, 2002; January, February, 2003).

Note: B. Kanegsberg is a member of the ASTM F04.15.17 working group concerned with “Standard Test Method for Assessing Extractable Residue in Implantable Metallic Components.” Observations are based on participation at the April 21, 2004 ASTM meetings, Salt Lake City, UT.