Essential prerequisites for any injectable product are its sterility, its freedom from pathogens and its freedom from visible particle contamination . . . . These requirements must be satisfied prior to the release of an injectable product batch for sale and use.A major difficulty in responding to these assay requirements is the need for a size sensitivity difference of 100 or greater in determining the presence of viable pathogenic organisms and of non-viable random particle contaminants. The wide dynamic testing range cannot be satisfied in current art with a single non-destructive testing station. The present invention uses a special agitation procedure to generate separate liquid volumes containing the small viable and larger non-viable particle contaminants. This separation makes possible the introduction of sensing systems that have been optimized for each size range and that can operate in parallel without interference.