The possibility of adapting the Standard Addition Method (SAM) to calibration in very difficult analytical conditions, namely when there is a need to determine an analyte with the use of nonlinear calibration graph and in the presence of matrix components causing additive interference effect, is investigated. To this aim the SAM in the common version and the Chemical H-point Standard Addition Method (C-HPSAM) realized by the flow injection technique were applied. Specifically, a flow manifold was used for construction of a set of nonlinear calibration graphs in different chemical conditions. As the graphs were intersected indicating both the additive interference effect and the analytical result free of this effect, the analyte concentration in the sample was able to be obtained with improved accuracy. The applicability of this approach was verified on the example of spectrophotometric determination of paracetamol in pharmaceuticals and of total acidity in wines. The C-HPSAM method enabled complete compensation of the additive effect and obtaining analytical results at a relative error not exceeding 6.0%.Graphical abstract
The implementation of a new calibration approach, termed the Signal Increment Standard Addition Method (SI-SAM), to the potentiometric determination of potassium in the synthetic samples and certified reference materials, is investigated. SI-SAM is a modification of SAM that is based on the change in the way in which the extrapolation is carried out. The calibration graph is extrapolated to the intersection with the signal of the first standard solution, not to the abscissa. Potentiometry is the method of choice due to its simplicity, rapid measurements, wide linear range and fulfilment of green analytical principles. However, careful attention is required to the calibration procedure because various versions of the standard addition method, which are commonly used in potentiometry, may create some problems leading to serious systematic analytical errors. The present work proves that SI-SAM allows for the elimination of this drawback and, consequently, for the determination of the considered analyte with improved results, especially in terms of accuracy and precision.
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