Calibration Curve

Calibration Curve – A plot of the relationship between instrument response and analyte concentration, used to determine concentration of analytes calibrated for in test samples. The calibration solutions should include all elements of interest in the test samples, ideally at concentrations ‘bracketing’ the expected sample concentrations.

• Bracketing refers to calibration of points above and below the expected test value to allow for more precise determination of sample concentration. If a sample is expected to have ~7 ppm Ca, one may calibrate at 5 ppm and 10 ppm to ‘bracket’ this expected result.
• Typical calibration curves tend to have 2 – 5 points (concentrations) for all elements of interest. This means that customers will either need to purchase 2 – 5 calibration solutions, or one solution at a higher concentration that can be diluted in their lab to create 2 – 5 solutions. In some cases, customers will buy single element solutions for each of their analytes of interest to create all of their own solutions (this option is very time consuming and can be more prone to error).
• Ideally the more calibration points built into a calibration curve the more accurate the method should be. This also increases the robustness of the method and will allow a seasoned analyst to troubleshoot results faster and more accurately.
• See section on calibrants for calibration curve example.