What is a Calibration Curve used for?

• A. A graph of known concentrations used to determine the concentrations of the unknown or to verify the proper functioning of an analytical instrument.
• B. A chart showing data trends over time.
• C. A control chart used to track measurement drift.
• D. A set of random standards not used in analysis.

Answer: (D)

A calibration curve is a plot that links the instrument’s response to known concentrations so you can translate a measured signal into a concentration for an unknown sample. You create it by measuring the response for a set of standards with known concentrations, then fit a line (often linear) to those data. With the resulting equation, you can interpolate the concentration of an unknown from its measured signal. This curve also helps verify that the instrument is operating within its linear range and that the response is proportional to concentration.

The idea isn’t about trends over time or tracking drift, and standards that aren’t used in analysis aren’t part of a valid calibration.