Back-calculated accuracy in calibration curves refers to the agreement between measured concentrations and what?

Back-calculated accuracy in calibration curves refers to the agreement between measured concentrations and what?

• A. Nominal concentrations of calibration standards
• B. The calibration curve slope
• C. The measured retention times
• D. The internal standard response

Answer: (A)

Back-calculated accuracy focuses on how close the concentrations obtained by applying the calibration model to the instrument response are to the known, prepared concentrations of the calibration standards. You build the curve from standards with nominal concentrations, then use the curve to back-calculate what concentration would produce each measured response. If those back-calculated values align with the nominal concentrations, the calibration is accurate and unbiased for quantification of unknowns. The slope tells you how sensitive the response is but not how accurate the back-calculation is; retention times relate to when compounds elute, not to concentration accuracy; and the internal standard response is used for normalization, not the direct agreement between back-calculated and nominal concentrations.