Application of soft and hard modeling methods to resolve the three competitive complex formation of 13 lanthanide-Arsenazo III complexes

The applicability of soft and hard modeling methods was used to determine the formation constants of complexes between 3,6-bis[(2-arsonophenyl)azo]-4,5-dihydroxy-2,7-naphtalenedisulphonic acid disodium salt (Arsenazo III) and 13 lanthanides. The results showed that all the 13 lanthanides (M) studied form a similar type of complexes and spectral profiles with Arsenazo III (L) with three formation constants corresponding to M/L ratios of 1:1, 1:2, and 2:2.