Standard addition

Method in analytical chemistry
The Standard addition method, often used in analytical chemistry, quantifies the analyte present in an unknown. This method is useful for analyzing complex samples where a matrix effect interferes with the analyte signal. In comparison to the calibration curve method, the standard addition method has the advantage of the matrices of the unknown and standards being nearly identical. This minimizes the potential bias arising from the matrix effect when determining the concentration.

Standard addition involves adding known amounts of analyte to an unknown sample, a process known as spiking. By increasing the number of spikes, the analyst can extrapolate for the analyte concentration in the unknown that has not been spiked. There are multiple approaches to the standard addition. The following section summarize each approach.

In classic polarography, the standard addition method involves creating two samples – one sample without any spikes, and another one with spikes. By comparing the current measured from two samples, the amount of analyte in the unknown is determined. In his polarography practical book, titled Chemische Analysen mit dem Polargraphen, Hohn referred this method as Eizhusatzes, which translates to "calibration addition" in English. Later in the German literature, this method was called as Standardzugabe, meaning "standard addition" in English. Modern polarography typically involves using three solutions: the standard solution, the unknown solution, and a mixture of the standard and unknown solution. By measuring any two of these solutions, the unknown concentration is calculated.