Materials Characterization: Differentiating Leachables and Extractables

When it comes to materials characterization, many people in the medical device industry tend to confuse leachables and extractables or use the terms interchangeably, David Albert, senior scientist and chief chemist at NAMSA, observed during a presentation at the MEDevice Forum in San Diego this week. And while it's understandable to do so, Albert notes, each term has a distinct meaning that is important to grasp.

"Extractables are chemical additives and byproducts extracted from devices or materials under exaggerated temperature and time conditions in organic solvents, waters, or buffers," Albert explains. He adds that they can be helpful in identifying potential leachables as well as in selecting the most suitable material for a given medical application.

Furthermore, extractables are becoming increasingly important for materials characterization, Albert says. "Something we're seeing a huge emphasis on from notified bodies and FDA today is validated methods. They want to make sure that you can detect all of the chemicals that are extracting but also at what level you can extract those things."

Such information, he adds, assists in determining toxicological risks and potential reactions that chemicals can induce in patients, including red eyes and dermatological reactions, for example. "That is why chemistry is now taking on [a more] unique position in biocompatibility today than it ever has before. [We need to] try to understand what we're dealing with and at what level is the exposure to these various chemicals," Albert notes.

Although extractables are becoming increasingly critical in materials' chemical characterization, leachables are important to understand as well. "Those are chemicals that migrate spontaneously from the materials under recommended conditions of use-that is, simulated physiologic conditions," Albert states. "The interesting thing is that these leachables are a subset of the extractables that we deal with in chemistry." --Shana Leonard