The acyl substituents of N,N-disubstituted N'-acylthioureas have a significant influence on the polarity of the chelates formed. A considerable decrease in the stability of the complexes is observed changing from aromatic to aliphatic acyl substituents. In order to separate the acylthiourea complexes, high performance thin-layer chromatography (HPTLC) methods have been used, whereby both standard methods, adsorption chromatography on silicagel layers and RP-chromatography are applicable. The strong UV-absorption properties of acylthiourea chelates allow a very sensitive detection of the separated complexes. By the method described several metals can be determined simultaneously on a migration distance of 2 to 5 cm.