“…129 On the other hand, various typical cryptands (221, 222 and 222B) have allowed the extraction of various metals such as Cu (II) , Tl (I) , Mn (II) and Pb (II) at neutral pHs in solvents like chloroform, dichloromethane and toluene, using eosin or erythrosin as the counterion, and detection by FAAS. [130][131][132][133] Many sorbents can better preconcentrate alkaline earth and transition elements (Ni, Pb, Cu, Co, Mn, Cd and Zn) simultaneously in neutral solutions because the metal cation is less affected by the hydroxyl groups and the ligands by protons. However, identical sorbents can better selectively separate precious metals (Pt, Pd, Ag and Au) under acidic conditions because metal cations solubilise better.…”