A clean sample (e.g., distilled water) processed through the instrumental steps of the measurement process to determine instrument contamination is called what?

• A. Method Blank
• B. Instrument Blank
• C. Surrogate
• D. Reagent Blank

Answer: (B)

Instrument blanks are used to check for contaminants that come from the measuring instrument itself. By running a clean solvent or blank sample through the full instrument path—everything from the sample introduction through detection—any signal that appears is due to the instrument or carryover, not an analyte. In your example, distilled water is prepared and processed just like real samples, so if you detect any signal, you know there’s instrument-related contamination that could affect measurements of actual samples. This distinguishes it from other blanks: a reagent blank tests for contaminants in the reagents and solvents used, a method blank goes through the entire method including sample prep to catch contamination from reagents and processing steps, and a surrogate is a known compound added to samples to monitor method performance rather than to detect instrument contamination.