The generalized H-point standard-additions method to determine analytes present in two different chemical forms in unknown matrix samples - Part II. Cr(VI)-determination in water samples by absorption spectrophotometry

The generalized H-point standard-additions method (GHPSAM) is used in order to obtain the total Cr(VI) and chromate concentration in water samples who se matrices are completely unknown. Moreover, a new methodology, which is a modification of the GHPSAM, is proposed for the simultaneous determination of the two major chemical forms of Cr(VI) present in the sample. The metho d is based on the location of spectral intervals where the behaviour of the interferent absorbance can be considered as linear. From these intervals, the analyte concentration free from bias error can be estimated. Spiked sam ples of dig and harbour water measured in the UV-visible spectral region ha ve been tested to check the background signal cancellation.