FLOW-INJECTION SPECTROPHOTOMETRIC DETERMINATION OF LYSINE IN FEED SAMPLES

A flow-injection spectrophotometric method is described for the determ ination of lysine, based on the product of the reaction between lysine and 1,2-naphthoquinone-4-sulphonate in basic medium. The influence of different physical, chemical and hydrodynamic parameters on absorbanc e were studied. At 480 nm, the response is linear up to 1.5 X 10(-4) M , the detection limit is 1.9 x 10(-6) M and the relative standard devi ation is 0.8%. Sample throughput is 80 h-1. The method was applied to the determination of free lysine in commercial feed samples, by means of multivariate calibration techniques, without the need of chromatogr aphic separation. Good concordance is shown between this method and th e standard procedure for amino acid analysis.