What is the purpose of field blanks in QA/QC?

• A. Field blanks help identify contamination introduced during field sampling and handling
• B. Field blanks measure ambient concentration
• C. Field blanks are used to calibrate instruments
• D. Field blanks replace lab blanks

Answer: (A)

Field blanks are used to detect contamination that can be introduced during the field sampling and handling process. By running a clean matrix through the same steps as real samples—opening, handling, transport, and storage in the field—any substances that appear in the blank point to contamination from sampling equipment, reagents, or handling practices rather than from the environment being measured. This helps ensure the data are trustworthy by identifying QA/QC issues in the field.

They don’t measure ambient concentration, since they contain no analyte and are specifically there to reveal contamination during collection. They aren’t used to calibrate instruments, which relies on calibration standards. They don’t replace lab blanks, which check for contamination introduced during lab processing.