kalibrationskurva

Kalibrationskurva, often translated as calibration curve, is a plot used in analytical methods to relate an instrument’s response to the concentration of an analyte. It is essential for quantitative analysis in fields such as chemistry, biochemistry, clinical diagnostics, environmental testing, and food safety.

Construction: A set of calibration standards with known concentrations spanning the expected measurement range is prepared. Each standard is measured under the same conditions as unknown samples; the instrument response (for example, peak area, absorbance, or detector signal) is recorded. The response is plotted against concentration, and a regression model—usually a linear least-squares fit—is applied to obtain an equation y = mx + b. The curve is evaluated by goodness-of-fit metrics such as R^2, and weighting may be used to compensate for heteroscedastic data. The linear range is the concentration interval where the response is proportional to concentration.

Use: To determine the concentration of an unknown, its response is measured and substituted into the calibration equation. Calibration is performed with blanks and quality-control samples; internal standards may be used to improve accuracy by correcting for variability.

Validation and limitations: Calibration must reflect the same assay conditions as the samples. Matrix effects can bias results; extrapolation beyond the calibration range should be avoided. Nonlinearity may require nonlinear regression or a piecewise calibration. Limits of detection (LOD) and quantification (LOQ) are often estimated from the calibration data.

Applications: Calibration curves are used in chromatography, UV–visible spectrophotometry, fluorescence, mass spectrometry, and immunoassays, among others. The Swedish term kalibrationskurva is commonly used in laboratory practice.