Multivariate curve resolution and trilinear decomposition methods in the analysis of stopped-flow kinetic data for binary amino acid mixtures

A stopped-now method is proposed to carry out the kinetic development of the reaction between amino acids and 1,2-naphthoquinone-4-sulfonate by mixing analytes and reagent in a three-channel continuous-now system. The process is monitored using a diode array spectrophotometer. Thus, every sample produces a data matrix built up from the spectra registered at regular steps of time. As the reaction is faster for secondary amino acids than for primary ones, it is possible to distinguish between the kinetic formation of their corresponding derivatives. The method is applied to the simultaneous determination of phenylalanine and proline by using second-order multivariate curve resolution. The derivatives of these two amino acids present some differences in both orders of measure, i.e., their spectra and kinetic profiles, which can be exploited advantageously to quantify one of the analytes in the presence of the other as interference, without including any information about this interference in the modeling of the system.