What is the purpose of using a blank sample in analysis?

• A. To calibrate the instrument at the start of the run.
• B. To detect contamination during sample handling, preparation, and/or analysis.
• C. To replace a sample that was lost.
• D. To compare results across laboratories.

Answer: (B)

The main idea is that blanks reveal background signals and contamination in the analysis. A blank contains all the solvents and reagents but no analyte, so any signal detected comes from impurities, the reagents themselves, glassware, or carryover from previous runs. This baseline lets you see whether contamination or background interference is present and how big it is. If the blank shows no signal, you can trust that the measured signals come from the actual samples; if the blank has a signal, you know there’s contamination or interference that needs to be addressed or subtracted from your sample results.

Calibrating the instrument relies on standards with known concentrations, not blanks. A blank isn’t used to replace a lost sample. While blanks help with consistency and quality control, they’re primarily about detecting background contamination rather than cross-lab comparison.