The peptidocalixarenes 1–3 bearing tryptophan, phenylglycine and leucil units at the lower rim and their complexes with alkali-metal (Li, Na, K, Rb, Cs) and selected lanthanide cations (La, Ce, Eu, Yb) were analyzed by ESI MS. The influences of the solvent (acetonitrile, methanol, addition of formic acid or sodium acetate) and the calixarene:cation molar ratio on signal intensities were investi...