IMPROVED SELECTIVITY IN MULTICOMPONENT DETERMINATIONS THROUGH INTERFERENCE MODELING BY APPLYING PARTIAL LEAST-SQUARES REGRESSION TO KINETICPROFILES

Binary and ternary mixtures of cysteine, tyrosine and tryptophan were used to show how kinetic methods together with partial least squares r egression (PLSR) can be used to overcome interferences in multicompone nt determinations; Two methods were compared: an equilibrium method wh ich uses the characteristic UV spectra of amino acids and a kinetic me thod which follows the reaction kinetics of the oxidation of the amino acids by hexacyanomanganate(IV). In both cases, multi-wavelength dete ction with a diode-array spectrophotometer was used. The results obtai ned from the two methods are critically compared. Lower concentrations of tyrosine and tryptophan can be determined by the equilibrium metho d because of their high absorptivities. On the other hand, the kinetic method, in conjunction with PLSR, can be considered an example of how selectivity can be improved. This allowed the resolution of mixtures of tyrosine and tryptophan in the presence of several complex spiked m atrices (aqueous extracts of feed samples that interfere to different extents) without any previous separation.