What is the purpose of field blanks in a QA/QC program for environmental sampling?

• A. To calibrate instruments.
• B. To detect contamination introduced during sampling and analysis.
• C. To store samples.
• D. To speed up lab work.

Answer: (B)

Field blanks are used to reveal any contamination that could be introduced during the sampling process itself. They are prepared in the field under the same handling and exposure conditions as real samples, except they do not contain actual environmental material. The blank goes through the same chain of custody, transport, storage, and laboratory analysis.

If the field blank shows detectable levels of analytes, it indicates contamination from sampling equipment, bottles, preservatives, gloves, or other field conditions. This helps you identify where errors may have occurred and decide whether to re-sample or adjust how results are interpreted. If the field blank is clean, but the real samples show contaminants, you can have greater confidence that those findings originate from the environment rather than from the sampling process. These blanks are not for calibrating instruments, storing samples, or speeding up lab work; those roles are filled by other QA/QC practices and controls.