6533b853fe1ef96bd12abfbc

RESEARCH PRODUCT

H-Point standard additions method for resolution of binary mixtures with simultaneous addition of both analytes

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Abstract The basis of the H-point standard additions method, HPSAM, with simultaneous addition of both analytes is proposed for the resolution of binary mixtures. It is a modification of the previously described H-point standard additions method that permits the resolution of both species from a unique calibration set by making the simultaneous addition of the two analytes. The method uses as analytical signals the absorbances at pairs of wavelengths where each species shows the same absorbance. The required data to apply the method are the absorbance values at the previously selected wavelengths for the sample alone and spiked with both species at known concentrations. Linear relations between absorbance values and added concentration of analyte are found, and the intersection of the lines at the previously selected wavelengths permits to obtain the analyte concentration in the sample. Wavelength pairs can be selected to obtain the most precise results. The effect of the relation of the concentrations of the two species in the standard and in the sample has been studied. Some mixtures of phenol and o-cresol, species highly overlapped (absorption maxima: for phenol at 234.6 and 287.0 nm; for o-cresol at 236.6 and 288.4 nm) and with similar absorptivities have been tested. If the matrix effect is known to be absent, the method can be employed with absortivity coefficients of the pure compounds.