calibration curve

**Calibration Curve** is a **mathematical relationship between the instrument response and the known concentration or property value of calibration standards** — typically a plot of signal (intensity, counts, absorbance) vs. known value, fitted with a regression model to convert measured signals into quantitative results. **Calibration Curve Construction** - **Standards**: Prepare 5-7+ calibration standards spanning the expected measurement range — plus a blank (zero standard). - **Measurement**: Measure each standard — record the instrument response (signal). - **Regression**: Fit a model (linear, quadratic, or weighted) to the signal vs. concentration data. - **R²**: Correlation coefficient should be >0.999 for linear calibration — indicates good fit. **Why It Matters** - **Quantification**: The calibration curve converts raw instrument signals into meaningful concentration values — the basis of quantitative analysis. - **Range**: The calibration curve defines the valid measurement range — extrapolation beyond the curve is unreliable. - **Frequency**: Calibration curves should be refreshed regularly or verified — instrument drift changes the curve. **Calibration Curve** is **the translator from signals to numbers** — the mathematical relationship that converts raw instrument responses into quantitative measurements.