Abstract
Several methods are described for the simultaneous determination of binary mixtures of xanthopterin (XAN) and isoxanthopterin (ISO) and of binary mixtures of xanthopterin and biopterin (BIO). The total luminiscence information from each compound has been used to optimize the most adequate analytical signal. A synchronous spectrofluorometric univariate procedure to analyze XAN and ISO is proposed. The procedure is compared with two multivariate procedures based on partial least-squares (PLS-1) and hybrid linear analysis (HLA/XS), by using synchronous spectral data as analytical signals. For the resolution of binary mixtures of XAN and BIO, a comparison between the predictive ability of the multivariate calibration methods, PLS-1 and HLA/XS, on two spectral data sets, excitation and emission spectra, has been performed. The calculation of the net analyte signal (NAS) by the HLA/XS method allows the determination of selectivity and sensitivity in each case. The proposed procedures are validated in the determination of several mixtures of these compounds, and the error values in a test set are reported.