Sampling is used extensively to monitor both behavior and quality throughout biopharmaceutical processesing (1, 2). Methods must deliver representative samples and — more important — not compromise the integrity of a given unit operation or the process of which it is part. When microorganisms, animal cells, viruses, or nonfilterable materials are involved, sampling methods must not introduce contamination (see the “Regulatory Requirements” box). For successful sampling, three methods have been used routinely over the years: steam-in-place (SIP) valves; aseptic tube…