What is a blank sample?

• A. A sample used to calibrate instrument response.
• B. A sample that lacks the parameters of interest. A blank sample result is used to detect contamination during sample handling, preparation, and/or analysis.
• C. A replicate of the sample to test precision.
• D. A sample spiked with known analyte.

Answer: (B)

A blank sample is made to contain everything except the analyte of interest. Its purpose is to reveal background signals and potential contamination from solvents, reagents, containers, or the instrument itself, so you can see what baseline noise looks like and detect issues that could affect real samples. This is why blanks are used to catch contamination that can occur during handling, preparation, and analysis, and they provide a baseline to subtract from measurements and help establish detection limits.

The other ideas don’t fit: a sample used to calibrate instrument response involves known amounts of analyte to set a response scale, which isn’t a blank; a replicate to test precision is about repeatability of measurements, not the empty baseline; and a sample spiked with known analyte is used to test recovery or method performance, not a true blank.