Measurement bench
Standards produce detector signals that define a straight calibration line.
Measurement sheet
| Standard / mol L⁻¹ | Signal / a.u. |
|---|
Concept figure
Greater concentration normally gives a greater signal for a positive-slope detector.
Live calibration plot
Standards and reference fit
Your line
Residuals
LOD
Instrument controls
Adjust the controls, then check your answer.
The maths
Linear calibration: signal = intercept + slope × concentration.
Least squares minimises Σ[signal − predicted signal]².
Unknown concentration = (unknown signal − intercept) / slope.
Limit of detection: LOD = 3.3 × residual standard deviation / slope. Residual SD uses n − 2 degrees of freedom.
For a sum, square weighted absolute uncertainties before adding. For a product or quotient, combine weighted relative uncertainties in quadrature. Inputs are treated as uncorrelated.