Determination of tryptophan in feed samples by cyclic voltammetry and multivariate calibration methods

A voltammetric method for the determination of tryptophan (Trp) in feed sam ples using multivariate calibration techniques is proposed. The multivariat e data consisted of the oxidation wave of cyclic voltammograms registered f rom 400 to 925 mV using a graphite-methacrylate composite electrode, at whi ch Trp was oxidized around a potential of 900 mV. The interference from oth er oxidizable amino acids as well as the feed sample matrix was circumvente d by using multivariate calibration methods. principal component regression (PCR) and partial least squares regression (PLS) and non-linear PLS (NL-PL S) were checked for quantifying Trp in these samples. The results obtained using NL-PLS were in agreement with those obtained with the standard method for the determination of amino acids, with an overall prediction error of 7.9%.