A New SBSE Method for Detecting Leachables

Medical implants can often contain contaminants, which come from their packaging or from the manufacturing of their polymer and metal components, or can form after the implant’s placement inside the patient. These contaminants, known as leachables, can make their way into a patient’s blood, endangering the patient’s health.

If leachables are discovered at concentrations that are too high, the product may not be approved by regulators such as the FDA. However, there are no legally binding upper limits for leachables in implants and prosthetics or any standard method for studying their concentrations. The Product Quality Research Institute does recommend a maximum exposure of 150 ng/day to genotoxic or carcinogenic leachables. Another challenge for studying leachables arises from the need to use large volumes of aqueous simulants to extract analytes, which are therefore at very low concentrations.

In a paper appearing in the Journal of Pharmaceutical and Biomedical Analysis, Gyorgy Vas, a researcher at Intertek, demonstrated a new method for studying potential leachables from whole implants that could yield results despite low concentrations. This method produced superior results to Solid Phase Micro Extraction (SPME) without the need for hazardous solvents.

Vas’ team studied ultra-high molecular weight polyethylene tibial knee inserts, which during manufacturing are often treated with the antioxidant 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (PBHP) to improve long-term product stability. Unfortunately, PBHP can degrade into byproducts that leach into surrounding tissue.

Vas’ team used the Twister, GERSTEL’s SBSE stir bar, to obtain organic compounds with higher recoveries and no use of solvents. Twisters were prepared for thermal desorption in the GERSTEL Thermal Desorption Unit (TDU), automated with the GERSTEL MultiPurpose Sampler (MPS). Desorbed analytes were cryogenically refocused in the GERSTEL Cooled Injection System, then separated by GC and analyzed with an MS/MS detector. All samples tested had detectable levels of antioxidant leachables, but none of the compounds found were leached from the implants above the recommended 150 ng/day. For longer-term degradation product detection, tests determined a linear range between 1.0 to 150 ng.

This method was then used on 11 tibial knee implants. Unlike traditional methods which only used fragments, Vas’ team could analyze a whole implant and run its sample tests with only minor manual steps, and without expensive, toxic solvents.

You can get more details about how Vas carried out his experiments, and review his results by reading the article, “Medical Implants—A Closer Look,” in GERSTEL Solutions Worldwide.

Then feel free to reach out for a deeper discussion on how we can improve your processes for studying leachables.