Diffusion-ordered H-1 NMR spectroscopy techniques have been used to determine the binding strength of p-sulfonatocalixarene (SO3) towards a number of charged crown ether species in aqueous conditions. For several (doubly) charged (di)azacrown ethers, all were bound by SO3 either well or very well with binding constants between 5.1 x 10(2) - 9.9 x 10(5) m(-1). These results correlate with, and thus explain the phenomenon of rapid capture of azacrown ethers in molecular capsules based on p-sulfonatocalixarene and lanthanide metals. Similarly, the formation of ``Russian doll'' superanions in the solution phase is also elucidated. These superanions have been shown to selectively crystallise particular polynuclear aquated metal ions from mixtures in the aqueous phase. Neutral crown-6 is not bound by p-sulfonatocalixarene and displays a binding constant of 0 m(-1). When sodium crown-6 is examined in a similar fashion, binding by SO3 is observed in solution with K-a similar to 3.1 x 10(3) m(-1).