H-point standard additions method for analyte determination in ternary mixtures
The use of the H-point standard additions method for resolving ternary mixtures is proposed. The method calculates the analyte concentration from spectral data at two wavelengths where the two species selected as interferents present the same absorbance relationship. These wavelength pairs are easily found, and can be selected to give the most precise results. If a matrix effect is present, use of the standard additions method is necessary in order to obtain good results. If there is no matrix effect, only sample absorbances and molar absorption coefficients are necessary. Ternary mixtures of phenol, o-cresol, 4-chlorophenol and 3,4-dichlorophenol, which are species with highly overlapped spectra throughout the wavelength range, were selected to test the method. The results obtained are comparable to those obtained using multilinear regression.