Standard addition method

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The standard addition method or the standard admixing method is a possibility in analytical chemistry to create a calibration for quantitative determinations. The name refers to the addition of a standard (or analyte) to the analysis sample .

As a rule, a calibration function is created for calibration. For this purpose, a series of solutions of different concentrations is usually made from an artificial stock solution ( dilution series ). The calibration solutions and all samples are each measured once. The analyte concentration in the sample can be calculated using the calibration function.

With the standard addition method, however, a certain amount of analyte is added several times to each sample and the sample is measured after each addition. The increase in the analyte signal is determined. By linear regression , the concentration of the analyte can be calculated in the original sample. The calibration function is generated from the sample by adding analyte (“spiking”). In the optimal case, the added proportion of the analyte should be in the same order of magnitude as the concentration of the analyte in the original sample, which requires some prior knowledge of the sample content.

With the standard addition method, instrumental errors and interferences can be minimized, especially when measuring in low concentration ranges ( trace analysis , investigations of recovery rates for method validation ). The standard addition method is advantageous when the analyte signal is strongly influenced by the sample matrix (especially with complex matrices). Then matrix-adapted calibration standards would have to be available for normal calibration, which is usually not possible. The internal standard procedure is also only suitable to a limited extent for complex matrices.

The method of standard addition requires a linear response behavior of the analytical method and the exact dosability of the analyte as a standard addition. The advantage of standard addition is that matrix effects can be corrected. Disadvantages are the increased workload and possible problems when exceeding the linear range of the analytical method.

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  • DIN 32633: "Method of standard addition"