Specific colour reaction for the determination of lysine and/or ornithine

A simple procedure was worked out for the direct spectrophotometric determination of lysine and/or ornithine in hydrolysates of proteins and protein-containing materials. The method is based on the estimation of the coloured compound formed in the reaction of lysine and ornithine with furfurol. Since the reaction is specific for lysine and ornithine and separation of amino acids is not necessary for their determination the method is suitable for large scale screening of protein samples. The lower limit of detection is 0.5 mug for lysine and 2 mug for ornithine and the accuracy of the method is +/- 0.5% and +/- 2% respectively.