Generalized H-point standard additions method for analyte determinations in unknown samples

The generalized H-point standard additions method (GHPSAM) is proposed. The method locates the linear spectral behaviour for the unknown global interference, if it exists, in all the spectral regions measured. The linear spectral interval for the interference is located from second derivative data. After this, the method validates the linearity supposition and estimates the analyte concentration free from bias error. So, only the data measured from the method are enough to obtain the unbiased analyte concentration in the presence of unknown interferences. Mixtures of phenol and 4-chloro-2-nitrophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol have been tested in order to check the validity of the method. The method also has been applied to the determination of amphetamine in urine samples. It works well in a lot of spectral situations, except in the cases when the global interference and the analyte are linear in the same spectral region.