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

Abstract

A voltammetric method for the determination of tryptophan (Trp) in feed samples using multivariate calibration techniques is proposed. The multivariate data consisted of the oxidation wave of cyclic voltammograms registered from 400 to 925 mV using a graphite–methacrylate composite electrode, at which Trp was oxidized around a potential of 900 mV. The interference from other oxidizable amino acids as well as the feed sample matrix was circumvented by using multivariate calibration methods. Principal component regression (PCR) and partial least squares regression (PLS) and non-linear PLS (NL-PLS) 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%.