Quantitative determination of monosubstituted guanidines: a comparative study of different procedures

Analysis of N2-acyl arginine derivatives as well as of arginine analogs lacking in alpha-amino function by Weber's modification of the Sakaguchi procedure yielded colored complexes with absorbance values approximately twice that obtained with an equivalent concentration of unmodified arginine. The limitations concerning the applicability of the various modifications of the Sakaguchi procedure as well as of the fluorimetric assay to the quantitative estimation of a variety of monosubstituted guanidines and proteins are discussed.