Simultaneous determination of several amino acids with multivariate calibration methods by using a continuous-flow system

Abstract

An initial approach to the simultaneous determination of several amino acids by using multivariate calibration methods is proposed. The method is based on the development of the reaction between amino acids and 1,2-naphthoquinone-4-sulfonate. Spectra of the corresponding derivatives obtained from a continuous-flow system were used to provide multivariate data for the multivariate procedure. Two multivariate calibration methods were applied, principal component regression (PCR) and partial least-squares regression (PLS). In order to compare the resolution capabilities of these multivariate methods, a series of synthetic solutions containing different concentrations of lysine, proline, phenylalanine and tryptophan were prepared. The selection of solutions for calibration and problem sets was performed on the basis of the distribution of the amino acid derivatives spectra on the first and second principal components. The effects of the number of working wavelengths, the number of principal components and the mathematical treatment of data (smoothed and derivative spectra) on the predictions were also investigated. The method was applied to the analysis of feed samples, where the determination of some particular amino acids such as lysine are of special interest. The results were in good agreement with those obtained with the standard amino acid autoanalyser procedure.