In sorbent tube sampling, which statement correctly defines a blank?

• A. A sorbent tube blank is not exposed to air to assess background contamination from handling or storage.
• B. A sorbent tube blank is used to collect the actual air sample.
• C. A sorbent tube blank is a standard reference material.
• D. A sorbent tube blank is a device to calibrate the pump flow.

Answer: (A)

A blank in sorbent tube sampling represents a tube that is not exposed to the air being tested, so any analyte detected would come from background sources such as handling, storage, or the tube material itself. This is crucial for QA/QC because it helps separate real sample results from contamination introduced during preparation or handling, allowing you to correct or flag results accordingly. It’s not meant to collect the actual air sample, it isn’t a standard reference material, and it isn’t used to calibrate pump flow.