No abstract

Actinomycins, which belong to a family of chromopeptide antibiotics, consist of a hetero-tricyclic chromophore to which are attached two pentapeptide chains either identical or different in amino acid sequence. The classification of existing actinomycins and the identification of new actinomycins are dependent on the characterization and quantitation of the amino acids present in the peptide chains. A simple, fast and highly reliable two-dimensional separation technique employing electrophoresis in a formic acid/acetic acid buffer (pH 1.9) on thin layers of microcrystalline cellulose followed by thin-layer chromatography with an n-butanol:water:glacial acetic acid (50:40:10) solvent system in a direction perpendicular to the electrophoresis was developed to separate the amino acids contained in hydrolysates of the actinomycins. The separated amino acids were identified by two parameters, the chromatographic Rf value and the electrophoretic mobility calculated relative to some standard migrating compound.

An analytical procedure is described for the determination of 1-(2-aminoethyl)-3-(2,6-dichlorophenyl) thiourea in dietary admix. Because of the complex nature of the carrier matrix, sample cleanup was required prior to HPLC separation. Sample cleanup was achieved using a cation-exchange microcolumn which yield highly reproducible results. HPLC separation was accomplished using a 10 mu C18 column, monitoring the column effluent in the ultraviolet region at 254 nm. After sample cleanup, 1-(2-aminoethyl)-3-(2,6-dichlorophenyl) thiourea could be detected at levels as low as 3 ppm in dietary admix.

No abstract