SPECTROPHOTOMETRIC DETERMINATION OF LYSINE IN THE PRESENCE OF OTHER AMINO-ACIDS AND PROTEINS USING FURFURALDEHYDE

The selective reaction of lysine, delta-hydroxylysine, ornithine and alpha,epsilon-diaminopimelic acid with furfuraldehyde, in anhydrous media, was investigated at 80, 85, 90 and 95-degrees-C by spectrophotometry, in the presence of various additional materials, such as potassium pyrosulphite, ascorbic acid and lead(II) acetate. Second-order rate constants and molar absorptivities were determined. Optimum conditions were established for the selective determination of lysine in the presence of intact proteins or in protein hydrolysates in the presence of a wide range of other amino acids including ornithine. Under optimum conditions, in the concentration range 2 x 10(-8)-3 x 10(-7) M, molar absorptivities and reproducibility data were measured with a standard error of 0.9-5.0%, depending on the procedure applied and on the amount of lysine present.