Vincent Van Nostrand

The correlation between swab assay results and visible-residue limits (VRLs) for cleaning validation was examined. Previously completed validation studies were reviewed to compare swab results with recently determined VRLs. A current cleaning validation study evaluated both swab testing and VRL. Unexpected swab results led to an investigation, which showed the value of establishing the VRL in conjunction with swab recoveries for cleaning validation programs.

Before formal cleaning validation programs were instituted, visual inspection was the primary means of determining equipment cleanliness. The use of visual inspection is still typically a component of a cleaning validation program and for routine inspections of cleaning effectiveness, but the use of visual inspection as a sole criterion for equipment cleanliness has not been successfully implemented as a valid approach for cleaning validation.

Formulation residue, observer viewing distance, light intensity, viewing angle, observer viewing position, and observer-to-observer variability affect the ability to confirm the cleanliness of manufacturing equipment.

Formulation residue, observer viewing distance, light intensity, viewing angle, observer viewing position, and observer-to-observer variability affect the ability to confirm the cleanliness of manufacturing equipment.

Evaluations have shown, in most cases, visual observations are sensitive enough to verify equipment cleanliness. An experiment was conducted to explore the possibility of using a visible-residue limit as an acceptable cleaning limit in a pharmaceutical research facility, including an evaluation of the limits and subjectivity of ?visually clean? equipment.