Comparison of the extrapolation precision of sequential and conventional standard addition calibrations

The precision of extrapolation for comparable cases of sequential standard addition calibration (S-SAC) and conventional standard addition calibration (C-SAC) are compared for various ratios of target analyte concentration and solution mass of the unknown solution to the standard solution. In addition the difference between homoscedastic and heteroscedastic analyser behaviour has been assessed. Whilst the precision of C-SAC is superior under most practical conditions it is not significant until the concentration of target analyte in the standard solution is less than ten times that of the unknown. The difference in extrapolation precision between C-SAC and S-SAC shows very little dependence on whether analyser behaviour is homoscedastic or heteroscedastic, or on the mass ratio of the unknown solution to the standard solution.