standard addition method (SAM)

The standard-addition  method  is a calibration method applied to reduce the effect of matrix interferences. It involves adding one or more increments of a standard solution to a sample  aliquots of the same size. Each spiked sample is then diluted to a fixed volume before analyzing. When  the amount of sample is limited, standard additions can also be carried out by successive introductions of increments  of the standard to a single measured aliquot of the unknown. Measurements are made on the original and after each addition. Placing a regression line through the absorptive data points obtained from the series of additions and interpolating it till crossing the abscissa, yields the initial analyte concentration of the sample.