Question

analytic chemistry

What is the advantage of using Standard Addition rather than directly measuring a sample?

I made two calibration curve , one with IS and one without IS.

Answer 1

With using a standard addition method the influence of matrix presented in sample is reduced. But standard addition corrects only for multiplicative interferences ,changes in calibration curve slope, not additive interferences changes in calibration intercept, such as spectral interferences. The method of standard addition is used in instrumental analysis to determine concentration of a substance in an unknown sample by comparison to a set of samples of known concentration, similar to using a calibration curve. Standard addition can be applied to most analytical techniques and is used instead of a calibration curve to solve the matrix effect problem. Standard addition is frequently used in atomic absorption spectroscopy and gas chromatography. The matrix effect problem occurs when the unknown sample contains many impurities. If impurities present in the unknown interact with the analyte to change the instrumental response or themselves produce an instrumental response, then a calibration curve based on pure analyte samples will give an incorrect determination.