Alternative Solvents for Extractables and Leachables Evaluation

The authors examine alternative solvents for evaluation of process components that provide extraction equivalence and do not interfere chromatographically.

Extractables and leachables evaluation of packaging components and components of bioprocessing systems is a crucial regulatory requirement. Solvents used for evaluation of process components may include surfactants that can interfere with chromatographic detection and contaminate the chromatographic system. The authors examine alternative solvents that provide extraction equivalence and do not interfere chromatographically.

Since the FDA Guidance for Industry: Container Closure Systems for Packaging Human Drugs and Biologics was issued in May of 1999 (1), extractables and leachables evaluation of final packaging components has become an increasing priority of FDA. The regulation on equipment construction (applicable to bioprocessing system components) as per CFR Part 211.65 states: "Equipment shall be constructed so that surfaces that contact components, in-process materials, or drug products shall not be reactive, additive, or absorptive so as to alter the safety, identity, strength, quality, or purity of the drug product beyond the official or other established requirements" (1, 2). Every new drug application is expected to include some form of extractables profiling and leachables evaluation for the components at highest risk and in closest contact with the drug. In addition to final container-closure systems, components associated with the bioprocessing system of biologics are considered at risk for leachables. Shelf life, storage temperature, and conditions of real-time use of a component under evaluation with the process stream, drug substance, or a final drug product are all key factors in designing appropriate extractables studies, simulation studies, and ultimately leachables studies (3).

To demonstrate that a container-closure system or a bioprocessing component is suitable for its intended use, the components typically undergo an initial extractables screening. The design of the extraction experiment should appropriately exaggerate the conditions of real-time use without breaking down or degrading the polymeric component under testing. Although strong polar and strong nonpolar solvents, such as 100% isopropanol (IPA) and 100% hexanes, are commonly used for highly aggressive reflux or soxhlet extractions of final container-closure systems that typically contain the final drug product for extended periods of time, these solvents are not always appropriate for the components of bioprocessing systems, such as bioprocess bags, filters, tubing, O-rings, diaphragms, and gaskets (3, 4).

For bioprocessing components, initial extractables screening involves filling or immersing the component in a variety of model solvents that more closely represent the formulation and exaggerate the conditions of real-time use. The components are incubated in the solvent for a predetermined length of time at an elevated temperature, such as 40–60 °C for several days, weeks, or even months. This type of extraction is recommended over an aggressive reflux extraction because exposure of the formulation to bioprocessing components is usually very short, and the temperatures of real-time use are typically at or below 25 °C. Reflux extraction of bioprocessing components using strong polar or nonpolar solvents is commonly not recommended unless the real-time exposure of the formulation to the component is long or at temperatures greater than 25 °C and the component is compatible with the solvent (3, 4).

Many extractables studies have instead used model solvents that are comprised of the same excipients that are present in the process buffers, drug substances, or final drug-product formulations. These excipients often include surfactants, which are common ingredients in the formulations of biologics and are regarded as essential components of the model solvents to be used to generate extractables profiles. Surfactants, however, pose major chromatographic interferences when screening for nonvolatile organic compounds by high-performance liquid chromatography–mass spectrometry (HPLC–MS). The detection of extractable compounds may be masked by co-eluting surfactant peaks. In addition, high concentrations of these surfactants are problematic, as they can contaminate the HPLC–MS system. Dilution is not always a viable solution because sensitivity can be greatly affected. Therefore, alternative solvents that provide extraction equivalence and do not interfere chromatographically were examined.