Issues to Consider in Liquid Extraction Testing of Surfaces for Particulate Matter

Formulation ingredients, process fluids, drug substance, and drug product contact many types of material surfaces during the manufacturing of pharmaceuticals. To achieve the requirements for subvisible and visible particulate matter in final drug products, good manufacturing practice (cGMP) requires control over the cleanliness of contact surfaces with respect to particulate matter. For cell therapy and other aseptic processes where filtration to remove particulate matter may not be possible, particulate matter may accumulate with each process step and pose risks to final drug product purity. Quantitative measurement of particulate matter on contact surfaces provides essential data for risk assessments. Here we address the issues associated with the measurement of surface cleanliness via liquid extraction, and discuss approaches to assessing and reporting surface cleanliness.