Limits of the internal standard technique in chromatography

Abstract By use of the law of propagation of error it is possible to determine how the internal standard technique affects the reproducibility of a given chromatographic analysis. The usefulness of this procedure is demonstrated with practical examples. Guidelines are provided for the proper application of the internal standard technique in the analysis of drugs in biological materials. It can be shown that, in practice, an external calibration is often advantageous compared to the internal standard technique.